Ritual of the bedside exam

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Kind: captions
Language: en

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SALMAN KHAN: This is Sal again.

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I'm here at Stanford Medical
School with Doctor Abraham

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Verghese and what are
we going to talk about?

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ABRAHAM VERGHESE:
We're going to talk

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about the ritual of the
physical exam, the bedside exam.

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SALMAN KHAN: The physical
exam, the ritual--

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why do you call it a ritual?

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That's interesting that
you call it a ritual.

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ABRAHAM VERGHESE: Yeah,
I think the lesson

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I've learned from hanging around
with my anthropology colleagues

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here at Stanford is that rituals
are all about transformation.

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A ritual signals the
crossing of a threshold.

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You baptize to signal the
crossing of a threshold,

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we marry to signal our departure
from a life of solitude,

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loneliness, and misery
to one of eternal bliss.

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SALMAN KHAN: Yes.

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ABRAHAM VERGHESE:
So our lives are

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full of-- You shouldn't
be laughing Sal.

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SALMAN KHAN: No.

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It resonates so
strongly with me.

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ABRAHAM VERGHESE: So
crossing a threshold is

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why we have a ritual.

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And I would say that the
act of one individual

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coming to another, and telling
them things they wouldn't tell

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their rabbi or their preacher,
and then incredibly disrobing

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and allowing touch, I
would say that that signals

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a ritual of
incredible importance.

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And the fact that
we, in the postmodern

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sort of medical world,
have stopped seeing it

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that way and just see it as
another data gathering tool may

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work for us, but I don't think
it works for the patient.

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And I think that a major
disconnect between us

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and our patients is our
failure to see what they see,

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which is a profound ritual in
which they're highly invested.

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And we then come and just
stick our stethoscope

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on top of the shirt, or don't
examine them thoroughly,

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we are sort of short
changing ourselves

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of an important ritual.

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SALMAN KHAN: Yeah, and
I'll feel short changed.

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I'm kidding.

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Sorry.

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ABRAHAM VERGHESE: But
I'd love to list for you,

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if I may, those aspects of
what makes this a ritual.

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So if you look at
it, first of all

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there's always a
specialized space.

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You don't examine a patient
out in the corridor.

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It's always a special room, a
ceremonial room if you will.

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Mysterious looking objects on
the walls, a very specialized

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bed that you sit on.

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These are all signals
that this is a virtual.

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Then when the physician
walks in the physician

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often is wearing
a ceremonial garb,

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which happens to
be a white coat.

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SALMAN KHAN: Fascinating.

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This is interesting just from an
anthropological point of view.

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ABRAHAM VERGHESE: The physician
is wearing ceremonial garment.

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The patient is also
instructed to disrobe

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and gets a patient garment.

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SALMAN KHAN: Which
seems specially designed

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to put patients in a
position of weakness.

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ABRAHAM VERGHESE: I know.

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It's quite unfortunate.

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We should be rethinking
the [INAUDIBLE] garments

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[? major. ?]

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And then the physician then
begins a systematic exam,

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which at some level is
mysterious to the patient.

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It's not always
clear to the patient

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why the physician is
thumping on their chest

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or why the physician is
saying take a deep breath,

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or cross your arms, or stand
on tiptoe, or take your hand

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and touch your nose rapidly.

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So there's mysterious and
ritualistic aspects to it.

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And very often the
physician is using

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terms that are somewhat
Latinate and arcane, and utterly

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mysterious to the patient such
as fremitus, and percussion.

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SALMAN KHAN: What
does fremitus mean?

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ABRAHAM VERGHESE: Fremitus means
you ask the patient to say 99,

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and you listen, you put
your hand on their chest.

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You pick up the vibration,
and if they have consolidation

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or collapse the
fremitus is not what

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it should be compared
to the other side.

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SALMAN KHAN: The fremitus,
so was it the sound or the--

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ABRAHAM VERGHESE: It's
more like the vibration.

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Sound being transmitted
through and being picked up

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by your hand.

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SALMAN KHAN: Interesting.

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ABRAHAM VERGHESE:
So the thing that's

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most interesting to
me about the ritual

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is that the person
coming in might

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be a policeman, a
teacher, an entrepreneur,

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but in the process of
putting on that gown,

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and sitting on that
ceremonial chair,

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they have sort of been
stripped of all that identity,

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and they are taking on the
identity of being the patient.

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But conversely, I think there's
something very important that

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happens, which is that just
before this the patient has

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been vocalizing all their
symptoms and their complaints,

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and at that point the physician
could order ten tests,

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and go and look at
images, but there's

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something about the
physician then laying

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hands on the patient,
that sort of gives weight

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to what the patient
just talked about.

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You talk about
your belly hurting,

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and then this individual
carefully examines your belly.

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It's sort of
validating your soma.

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Your body is being
validated in this ritual.

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And then when you
finally have the tests

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all sent off they become sort
of-- what follows intuitively

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on the ritual of first having
it validated on your body.

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One of the things that
I bemoan sometimes

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is that at times the
patient in the bed,

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I feel, in hospitals
around America,

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has almost become an icon
for the real patient who's

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in the computer.

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SALMAN KHAN: Right.

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It's just something
to interface with

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to get to that data
structure in the computer.

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It's interesting.

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ABRAHAM VERGHESE:
I've coined a term

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for that entity in the computer.

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It's the iPatient.

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When the iPatient is getting
fabulous care the real patient

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I think has a need to feel
their complaints validated.

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To feel it validated
on their soma,

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and to engage in a ritual for
which there's a transformation.

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And you might well ask me,
what is the transformation

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that takes place in this ritual?

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And, I think the
transformation is

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the sense of the patient
has delivered the story,

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the physician in the
process of the ritual

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has validated that
they've heard the story

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and tried to locate
it on the soma,

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and the transformation
is really the ceiling

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of the patient
physician relationship.

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And so I think what
has happened Sal,

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unfortunately, is
that because we

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have so much technology we've
become very sloppy in the way

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we examine patients.

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I think that we should be a
hundredfold better at examining

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people given that we
have real-time feedback

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with echocardiograms,
angiograms, and all that.

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Instead of which, I
think people have never

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been less certain of
their bed side skills.

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SALMAN KHAN: What
about this phenomenon,

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just talking to physicians
I know in my own family,

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that there's so
much time pressure.

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They have to see so many
patients, one every 15 minutes,

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and all of this, and they
wish they could do this,

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but they'll say that I have
so many other things to worry

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about, and the
paperwork, and all that.

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Is it realistic?

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ABRAHAM VERGHESE: No, I think
that's a very real concern.

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But I think if you
can do this well.

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And our goal at Stanford
is to teach our students

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to do it very well.

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You actually save time.

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Because if you do a quick
exam and you find that they're

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tender in a certain spot you
can order the test that sources

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just that out,
rather than, which

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I think is much more common,
which is I don't really

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know what's going on,
I'll tick off every box,

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and maybe something will
fall out of the sky.

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So I think a directed exam,
not only fulfills the ritual,

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but if you're any good
at it, it actually

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allows you to ask better
questions of a test you order

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and minimize the patient's
exposure to radiation.

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And I think the trouble
is we get all these tests,

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and we get back
results we don't know

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what to do with, we stumble onto
what we call incidentalomas.

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Have you heard that term?

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SALMAN KHAN: Incidentaloma.

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Well, I have heard that VIP's
often get worse medical care

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because they do
everything for them.

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ABRAHAM VERGHESE:
Yeah, exactly and they

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wind up with finding things
they don't know what to do.

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SALMAN KHAN: Exactly yeah
over diagnosing things.

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ABRAHAM VERGHESE: But to
come back to a ritual,

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I think we at Stanford
are very proud to feel

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that, as much as we
represent this great bastion

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of technology and
advancement, we also celebrate

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the fundamental ritual aspects
of the patient physician

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relationship, which
is best symbolized

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in the physical exam.

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SALMAN KHAN: I think this
is why a lot of physicians

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originally want to
enter the field.

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It sometimes gets lost, but this
is why they wanted to do it.

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ABRAHAM VERGHESE:
And you're right.

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I think they often
get disappointed

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when they learn to do this
and arrive on the wards

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and find that no one's
carrying a stethoscope,

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and no one's carrying-- I mean
they carry the stethoscope.

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I think it's like
a mating symbol.

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SALMAN KHAN: No you gotta
carry one to look legitimate.

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ABRAHAM VERGHESE: But they
don't carry the knee hammer,

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and they don't carry
all the other tools.

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SALMAN KHAN: I once visited
my wife at the doctor

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and I wore her coat,
and I felt very good.

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ABRAHAM VERGHESE: Did you
drape your stethoscope

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around the neck too?

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SALMAN KHAN: Oh I did.

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Yeah, I looked
very authoritative.

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ABRAHAM VERGHESE: That's a
great signal that you arrived.

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So I think that we
have so much to learn

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from our anthropology colleagues
about the importance of ritual.

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I think sometimes we
operate as though medicine

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is all about reason, but it's
really reason, ritual, emotion.

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They all tie in together.

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This is art and science.

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SALMAN KHAN: No.

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This is fascinating.

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I'm going to reflect
on some of the rituals

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I do now to see if they are.

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Very cool.

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Well, thank you for this.

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ABRAHAM VERGHESE:
Thank you so much.


Childhood growth

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Language: en

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SAL KHAN: I'm here with
the Dr. Laura Bachrach

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at Stanford Medical School.

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And what are we
going to talk about?

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DR. LAURA BACHRACH:
We're going to talk

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about normal and abnormal
growth in children.

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SAL KHAN: Fascinating.

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DR. LAURA BACHRACH: So this
is an important concern.

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Parents really worry if their
child is growing normally.

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And physicians worry
about this too,

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because the change in height is
an important barometer of how

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the child is doing overall,
in terms of health.

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So to begin to assess the
child's growth pattern,

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we have to think about what
are the determinants of where

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the child should be
on the growth curve.

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The number one most important
determinant, of course,

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is genetics.

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Short parents are
more likely to have

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short children and vice versa.

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SAL KHAN: And that's true
even when a child is young,

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because sometimes I've
seen the opposite.

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So people who are petite
have large children

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and all the rest.

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But it is true that,
if someone is large,

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they're more likely to
have large children, even

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infants and toddlers.

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DR. LAURA BACHRACH: You've hit
upon a really important issue

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that's shown here in this slide.

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The size of a baby at
birth isn't necessarily

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going to reflect the genetics.

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There are babies that are
born small, because mother

00:01:05.370 --> 00:01:06.780
didn't have prenatal care.

00:01:06.780 --> 00:01:08.670
Mother was a smoker,
other factors

00:01:08.670 --> 00:01:11.340
that compromise the
growth of the child.

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And those babies
can be born small

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for their gestational age.

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During the first two
to three years of life,

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they have a chance to
catch up on the curve

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and reach what's called
their genetic potential.

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SAL KHAN: So let's
just make sure.

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I want to make sure.

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I've seen these
curves before, when

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I went to visit a
pediatrician, even

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I remember this when I used to
visit the pediatrician, which

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I did maybe a little too long.

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So this axis right
over here is age.

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DR. LAURA BACHRACH: In months.

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SAL KHAN: In months-- so
this is right here birth.

00:01:40.420 --> 00:01:41.800
This is birth.

00:01:41.800 --> 00:01:44.812
So if a baby is born
at-- I don't know.

00:01:44.812 --> 00:01:46.270
This is the weight
right over here.

00:01:46.270 --> 00:01:51.080
So if a baby is born at five
pounds-- is this in pounds?

00:01:51.080 --> 00:01:51.970
This is kilograms.

00:01:51.970 --> 00:01:54.957
OK, so five pounds
is right over.

00:01:54.957 --> 00:01:55.540
Is that right?

00:01:55.540 --> 00:01:57.770
Yeah, five pounds would
be right over here.

00:01:57.770 --> 00:01:59.615
So this would be a baby
born at five pounds.

00:01:59.615 --> 00:02:01.080
DR. LAURA BACHRACH: Right.

00:02:01.080 --> 00:02:04.130
And I'm talking more here,
during this growth lecture,

00:02:04.130 --> 00:02:08.009
about the height or
length of the baby,

00:02:08.009 --> 00:02:11.330
throughout babyhood
and childhood.

00:02:11.330 --> 00:02:14.500
But let's say, the baby
were born light in weight

00:02:14.500 --> 00:02:15.850
and short in length.

00:02:15.850 --> 00:02:18.320
SAL KHAN: So maybe
18 inches right here

00:02:18.320 --> 00:02:19.330
would be a short length.

00:02:19.330 --> 00:02:21.130
DR. LAURA BACHRACH:
Right, and let's say,

00:02:21.130 --> 00:02:25.110
that baby was small
because his mother

00:02:25.110 --> 00:02:27.035
had issues during the pregnancy.

00:02:27.035 --> 00:02:28.910
SAL KHAN: Is it always
the case that the baby

00:02:28.910 --> 00:02:30.390
will be small because of issues?

00:02:30.390 --> 00:02:33.470
DR. LAURA BACHRACH: No.

00:02:33.470 --> 00:02:35.160
The bottom line is
that genetics plays

00:02:35.160 --> 00:02:38.062
less of a part in the
size of the baby at birth

00:02:38.062 --> 00:02:39.520
than it will later
on in childhood.

00:02:39.520 --> 00:02:40.490
SAL KHAN: All right,
it makes sense.

00:02:40.490 --> 00:02:42.590
DR. LAURA BACHRACH: So to
come back to your point,

00:02:42.590 --> 00:02:44.560
you'll meet parents
whose baby seem

00:02:44.560 --> 00:02:46.770
to be larger or
smaller than they are.

00:02:46.770 --> 00:02:50.102
But by age three the
child should be--

00:02:50.102 --> 00:02:51.310
SAL KHAN: Hold on one second.

00:02:51.310 --> 00:02:52.930
Let me just close this.

00:02:52.930 --> 00:02:53.430
OK.

00:02:53.430 --> 00:02:54.804
DR. LAURA BACHRACH:
By age three,

00:02:54.804 --> 00:02:58.590
the child should be in
his or her genetic groove,

00:02:58.590 --> 00:02:59.200
if you will.

00:02:59.200 --> 00:03:00.070
SAL KHAN: I see.

00:03:00.070 --> 00:03:01.528
DR. LAURA BACHRACH:
So there can be

00:03:01.528 --> 00:03:04.180
movement on the growth curve
in the first two to three years

00:03:04.180 --> 00:03:04.710
of life.

00:03:04.710 --> 00:03:08.160
There can be catch-up growth,
where the child, who was small,

00:03:08.160 --> 00:03:10.120
let's say, moves
from below the curve

00:03:10.120 --> 00:03:13.144
up to the 50th percentile,
by age 24 months.

00:03:13.144 --> 00:03:14.560
SAL KHAN: So this
would be a child

00:03:14.560 --> 00:03:15.768
who does something like this.

00:03:15.768 --> 00:03:18.700
DR. LAURA BACHRACH:
Exactly, exactly.

00:03:18.700 --> 00:03:21.730
And you can have the converse,
where you have a very big baby.

00:03:21.730 --> 00:03:24.110
Let's say, mother had
uncontrolled diabetes,

00:03:24.110 --> 00:03:25.590
and the baby was
born very large.

00:03:25.590 --> 00:03:29.820
That baby can have catch-down
growth, to the 50th percentile.

00:03:29.820 --> 00:03:34.690
By the age of three, certainly
movement across percentiles

00:03:34.690 --> 00:03:40.650
is considered to be abnormal
and warrants an investigation.

00:03:40.650 --> 00:03:43.460
SAL KHAN: So you really can
predict someone's even adult

00:03:43.460 --> 00:03:46.065
height, based on
where they at three?

00:03:46.065 --> 00:03:48.800
DR. LAURA BACHRACH: A general
rule of thumb is, that by age 2

00:03:48.800 --> 00:03:51.450
and 1/2 to 3, the child is
in their genetic groove.

00:03:51.450 --> 00:03:52.770
SAL KHAN: Really?

00:03:52.770 --> 00:03:53.470
Oh, wow.

00:03:53.470 --> 00:03:55.460
I didn't realize that
quickly you can kind of--

00:03:55.460 --> 00:03:57.370
so if a child, at
age three or four,

00:03:57.370 --> 00:03:59.170
is in the 25th
percentile in height,

00:03:59.170 --> 00:04:02.362
it's unlikely that they're
going to be in the NBA?

00:04:02.362 --> 00:04:04.220
DR. LAURA BACHRACH: In
general, that's true.

00:04:04.220 --> 00:04:05.420
There are a few exceptions.

00:04:05.420 --> 00:04:07.750
There are late
bloomers, what we call

00:04:07.750 --> 00:04:09.990
a constitutional
delay of growth.

00:04:09.990 --> 00:04:12.580
But a general rule
would be, what

00:04:12.580 --> 00:04:14.710
percentile you are by
the age of two or three

00:04:14.710 --> 00:04:16.501
is pretty much where
you're going to track,

00:04:16.501 --> 00:04:18.040
if all things are
going normally.

00:04:18.040 --> 00:04:19.970
SAL KHAN: Wow, I never
realized that it was that soon.

00:04:19.970 --> 00:04:22.470
DR. LAURA BACHRACH: And genetics
is an important determinant

00:04:22.470 --> 00:04:23.520
as I said.

00:04:23.520 --> 00:04:26.880
We can actually do a
calculation of where

00:04:26.880 --> 00:04:30.020
we think a child should end
up, the so-called mid-parental

00:04:30.020 --> 00:04:33.000
height, which we are
going to talk about later.

00:04:33.000 --> 00:04:35.930
So genetics is the
critical factor.

00:04:35.930 --> 00:04:38.950
But whether or not you
reach your genetic potential

00:04:38.950 --> 00:04:42.750
means that the cards have to
be lined up appropriately.

00:04:42.750 --> 00:04:44.860
So the cards that are
important for achieving

00:04:44.860 --> 00:04:48.570
your genetic potentials, first
of all, number one-- normal

00:04:48.570 --> 00:04:52.430
amounts of hormones that
are important for growing.

00:04:52.430 --> 00:04:56.115
And those are thyroid and growth
hormone, to a large extent.

00:04:58.880 --> 00:05:02.910
A second factor, of course,
is adequate nutrition.

00:05:02.910 --> 00:05:04.860
And we think
worldwide of children

00:05:04.860 --> 00:05:08.820
who are undernourished,
who don't look anywhere

00:05:08.820 --> 00:05:10.540
near their age, in
terms of height,

00:05:10.540 --> 00:05:11.960
because they're
so undernourished.

00:05:11.960 --> 00:05:13.115
It really cramps their style.

00:05:13.115 --> 00:05:14.300
SAL KHAN: And you see
the reverse of that.

00:05:14.300 --> 00:05:16.354
I mean, I don't know
what I am officially.

00:05:16.354 --> 00:05:17.020
I was born here.

00:05:17.020 --> 00:05:17.610
My parents weren't.

00:05:17.610 --> 00:05:19.175
So I'm what, first generation
or second generation.

00:05:19.175 --> 00:05:20.860
But you see that in
that, is that you

00:05:20.860 --> 00:05:22.790
see a lot of people
in my generation

00:05:22.790 --> 00:05:24.670
are much taller
than their parents,

00:05:24.670 --> 00:05:26.140
because their
parents were probably

00:05:26.140 --> 00:05:27.350
malnourished in some way.

00:05:27.350 --> 00:05:28.010
DR. LAURA BACHRACH:
Certainly, there

00:05:28.010 --> 00:05:30.370
can be a secular trend,
where the children get taller

00:05:30.370 --> 00:05:33.150
than the parents,
if the children have

00:05:33.150 --> 00:05:34.830
a different environment.

00:05:34.830 --> 00:05:37.370
The other thing we notice
about nutrition in our country

00:05:37.370 --> 00:05:39.640
is the over-nutrition
of our children.

00:05:39.640 --> 00:05:45.080
And what happens with obesity is
that children may grow faster,

00:05:45.080 --> 00:05:49.160
in terms of both weight
and height for their age.

00:05:49.160 --> 00:05:51.220
They don't end up
taller in the long run.

00:05:51.220 --> 00:05:54.714
But they move ahead more quickly
through the maturation process.

00:05:54.714 --> 00:05:55.380
SAL KHAN: I see.

00:05:55.380 --> 00:05:55.963
I didn't know.

00:05:55.963 --> 00:05:56.950
OK, it can accelerate.

00:05:56.950 --> 00:05:59.687
DR. LAURA BACHRACH: Exactly.

00:05:59.687 --> 00:06:01.020
SAL KHAN: I never realized that.

00:06:01.020 --> 00:06:01.812
That's fascinating.

00:06:01.812 --> 00:06:03.353
DR. LAURA BACHRACH:
And then we think

00:06:03.353 --> 00:06:04.540
about psychosocial factors.

00:06:04.540 --> 00:06:07.500
There literally is
a situation where

00:06:07.500 --> 00:06:11.690
infants can be deprived of
parental love and support,

00:06:11.690 --> 00:06:13.350
and you see something
dwarfing there.

00:06:13.350 --> 00:06:16.290
In a teenager, we see problems
with eating disorders,

00:06:16.290 --> 00:06:19.287
that's a cross between nutrition
and a psychological problem.

00:06:19.287 --> 00:06:21.120
So psychosocial factors
play a role as well.

00:06:21.120 --> 00:06:23.550
SAL KHAN: So they've
shown, or it's

00:06:23.550 --> 00:06:25.380
been seen that it's
noticeable changes

00:06:25.380 --> 00:06:27.770
in physical development,
based on, I guess,

00:06:27.770 --> 00:06:29.042
attention and love.

00:06:29.042 --> 00:06:30.750
DR. LAURA BACHRACH:
Yes, there's actually

00:06:30.750 --> 00:06:32.840
a syndrome called
psychosocial dwarfism, where

00:06:32.840 --> 00:06:35.700
you can actually see
a slow down in growing

00:06:35.700 --> 00:06:38.280
without adequate
interpersonal support.

00:06:38.280 --> 00:06:40.035
SAL KHAN: Wow,
that's fascinating.

00:06:40.035 --> 00:06:43.710
DR. LAURA BACHRACH: So
the issue is, when do you

00:06:43.710 --> 00:06:48.470
need to worry about a
child's growth pattern?

00:06:48.470 --> 00:06:50.260
In order to interpret
that, you have

00:06:50.260 --> 00:06:54.580
to understand about the
variability in growth.

00:06:54.580 --> 00:06:56.730
In the first two to
three years of life,

00:06:56.730 --> 00:07:00.240
children grow much more quickly
than they will later on.

00:07:00.240 --> 00:07:02.710
By the age of three,
until they hit puberty,

00:07:02.710 --> 00:07:05.006
children should grow
two inches a year.

00:07:05.006 --> 00:07:07.434
SAL KHAN: Two inches a year,
this is from the ages of--

00:07:07.434 --> 00:07:09.100
DR. LAURA BACHRACH:
After they're out of

00:07:09.100 --> 00:07:10.614
toddlerhood until
they hit puberty.

00:07:10.614 --> 00:07:12.405
SAL KHAN: So this is
like three to puberty.

00:07:12.405 --> 00:07:14.840
DR. LAURA BACHRACH:
Exactly, exactly.

00:07:14.840 --> 00:07:18.910
But when kids will hit puberty
is going to be variable.

00:07:18.910 --> 00:07:21.940
And so that's an issue.

00:07:21.940 --> 00:07:24.360
If children are growing
at a normal rate,

00:07:24.360 --> 00:07:28.130
it's not necessary to
memorize the inches per year.

00:07:28.130 --> 00:07:30.040
Children will track
along the growth curve.

00:07:30.040 --> 00:07:34.010
And if we can turn to the
next slide or next graph,

00:07:34.010 --> 00:07:36.950
this is a graph for what
we use for older children,

00:07:36.950 --> 00:07:40.700
after the age of 2
up until they're 18.

00:07:40.700 --> 00:07:43.680
This is the curve that we use.

00:07:43.680 --> 00:07:46.040
Now, beyond the age
of two, I said to you,

00:07:46.040 --> 00:07:51.020
it's not normal for children to
necessarily cross percentiles.

00:07:51.020 --> 00:07:53.900
So if, for example,
you have a child

00:07:53.900 --> 00:07:57.570
who is tracking along the
fifth percentile every year,

00:07:57.570 --> 00:07:58.927
growing their two inches a year.

00:07:58.927 --> 00:08:00.510
SAL KHAN: This is
the fifth down here?

00:08:00.510 --> 00:08:02.510
DR. LAURA BACHRACH: Right,
the lower line there.

00:08:02.510 --> 00:08:04.780
They're moving along,
steadily, steadily, steadily.

00:08:04.780 --> 00:08:10.770
That child has a more reassuring
growth curve than one,

00:08:10.770 --> 00:08:13.080
for example, who
as a five-year-old

00:08:13.080 --> 00:08:14.786
had been at the
top of the curve.

00:08:14.786 --> 00:08:16.160
SAL KHAN: Right,
a five-year-old.

00:08:16.160 --> 00:08:17.665
So five-year-old is right there.

00:08:17.665 --> 00:08:19.415
DR. LAURA BACHRACH:
And then the next year

00:08:19.415 --> 00:08:21.505
is on the 75th
moving down a line.

00:08:21.505 --> 00:08:22.470
SAL KHAN: I see.

00:08:22.470 --> 00:08:24.053
DR. LAURA BACHRACH:
And the year after

00:08:24.053 --> 00:08:25.620
is on the 50th percentile.

00:08:25.620 --> 00:08:27.560
Now, at that point
in time, the child

00:08:27.560 --> 00:08:29.450
has theoretically
a normal height

00:08:29.450 --> 00:08:31.310
because it's within the curve.

00:08:31.310 --> 00:08:34.005
But there's something very
abnormal about that rate

00:08:34.005 --> 00:08:34.504
of growing.

00:08:34.504 --> 00:08:38.031
And that's the child that's
more worrisome than the shorter

00:08:38.031 --> 00:08:38.530
child.

00:08:38.530 --> 00:08:39.961
SAL KHAN: Fascinating.

00:08:39.961 --> 00:08:41.419
DR. LAURA BACHRACH:
So bottom line,

00:08:41.419 --> 00:08:43.070
when a child would
come in to present

00:08:43.070 --> 00:08:45.670
to me because of a
concern about growing,

00:08:45.670 --> 00:08:48.287
I'd first of all try to
decide if they're are short

00:08:48.287 --> 00:08:49.620
and if they're growing normally.

00:08:49.620 --> 00:08:52.260
And those are two
different questions.

00:08:52.260 --> 00:08:54.350
The first question
is, are they short?

00:08:54.350 --> 00:08:55.930
And are they short
can be defined

00:08:55.930 --> 00:08:57.630
by looking at these curves.

00:08:57.630 --> 00:09:00.140
These are curves
representing the spectrum

00:09:00.140 --> 00:09:03.040
of normal height for a
healthy American youth.

00:09:03.040 --> 00:09:06.612
And they go from the 5th
to the 95th percentile.

00:09:06.612 --> 00:09:10.950
So you can compare a child
to the population as a whole.

00:09:10.950 --> 00:09:13.170
But I also like
to calculate what

00:09:13.170 --> 00:09:15.510
we call the mid-parental height.

00:09:15.510 --> 00:09:17.560
OK, this is where
we take into account

00:09:17.560 --> 00:09:21.500
the heights of the
parents, because that's

00:09:21.500 --> 00:09:23.120
the most important determinant.

00:09:23.120 --> 00:09:26.580
So how we calculate
that is as follows.

00:09:26.580 --> 00:09:29.820
We take the height of mom
and dad and average them.

00:09:29.820 --> 00:09:31.370
SAL KHAN: OK, let's do that.

00:09:31.370 --> 00:09:34.152
So I'm 5' 9", if I'm
wearing decent shoes.

00:09:34.152 --> 00:09:35.110
DR. LAURA BACHRACH: OK.

00:09:35.110 --> 00:09:37.510
SAL KHAN: So set
that to 69 inches.

00:09:37.510 --> 00:09:38.730
DR. LAURA BACHRACH: OK.

00:09:38.730 --> 00:09:41.710
And how tall is the
mother of your children?

00:09:41.710 --> 00:09:42.800
SAL KHAN: She's 5' 6".

00:09:42.800 --> 00:09:43.370
DR. LAURA BACHRACH: She's 5' 6".

00:09:43.370 --> 00:09:46.100
SAL KHAN: Which is why I don't
let her wear too large heels.

00:09:46.100 --> 00:09:47.060
DR. LAURA BACHRACH: OK.

00:09:47.060 --> 00:09:49.790
And are we trying to calculate
your son or your daughter?

00:09:49.790 --> 00:09:52.010
SAL KHAN: Let's do my son,
since he's a little older.

00:09:52.010 --> 00:09:53.472
So let's see, it's
plus 66 inches.

00:09:53.472 --> 00:09:54.430
DR. LAURA BACHRACH: OK.

00:09:54.430 --> 00:09:56.370
So we'll take the
midpoint of that.

00:09:56.370 --> 00:09:58.540
SAL KHAN: OK, so that's
really an inch and 1/2.

00:09:58.540 --> 00:10:01.127
So it's what, 67 and 1/2
inches between me and my wife.

00:10:01.127 --> 00:10:02.210
DR. LAURA BACHRACH: Right.

00:10:02.210 --> 00:10:04.920
And we're going to
add 2 and 1/2 inches.

00:10:04.920 --> 00:10:05.720
SAL KHAN: OK.

00:10:05.720 --> 00:10:08.435
So that gets us what,
to exactly 70 inches.

00:10:08.435 --> 00:10:09.940
DR. LAURA BACHRACH: Right.

00:10:09.940 --> 00:10:12.381
And that's the height
prediction for your son.

00:10:12.381 --> 00:10:13.380
SAL KHAN: Oh, very good.

00:10:13.380 --> 00:10:14.310
DR. LAURA BACHRACH:
Plus or minus--

00:10:14.310 --> 00:10:15.630
SAL KHAN: Oh, plus or minus.

00:10:15.630 --> 00:10:16.350
DR. LAURA BACHRACH: 4 inches.

00:10:16.350 --> 00:10:17.300
SAL KHAN: Plus or
minus 4 inches,

00:10:17.300 --> 00:10:18.420
oh, that's a big difference.

00:10:18.420 --> 00:10:20.170
DR. LAURA BACHRACH:
It's a big difference.

00:10:20.170 --> 00:10:22.780
But that's the nature
of human variability.

00:10:22.780 --> 00:10:23.500
SAL KHAN: I see.

00:10:23.500 --> 00:10:24.458
DR. LAURA BACHRACH: OK.

00:10:24.458 --> 00:10:26.535
Now, if this were
your daughter, we

00:10:26.535 --> 00:10:30.560
would take the 67 and 1/2 inches
and subtract 2 and 1/2 inches.

00:10:30.560 --> 00:10:31.795
Let's do that.

00:10:31.795 --> 00:10:34.394
SAL KHAN: OK, so that
gets us 65, so 5' 5"

00:10:34.394 --> 00:10:36.560
DR. LAURA BACHRACH: Exactly,
plus or minus 4 inches.

00:10:36.560 --> 00:10:38.224
SAL KHAN: Plus or
minus 4 inches.

00:10:38.224 --> 00:10:40.140
DR. LAURA BACHRACH: So
that's something we do.

00:10:40.140 --> 00:10:44.670
We then calculate-- in
fact, let's plot that,

00:10:44.670 --> 00:10:45.570
right on the curve.

00:10:45.570 --> 00:10:49.865
This is the boys' curve, so
let's plot the 70 inches.

00:10:49.865 --> 00:10:53.840
SAL KHAN: 70 inches is
right over here, OK.

00:10:53.840 --> 00:10:57.690
DR. LAURA BACHRACH: And
then the range of 74.

00:10:57.690 --> 00:10:59.707
SAL KHAN: 74 to 66.

00:10:59.707 --> 00:11:02.040
DR. LAURA BACHRACH: Right,
exactly-- pretty broad range.

00:11:02.040 --> 00:11:02.580
SAL KHAN: Yes.

00:11:02.580 --> 00:11:03.538
DR. LAURA BACHRACH: OK.

00:11:03.538 --> 00:11:07.900
But if we had a child who was
growing well below the curve

00:11:07.900 --> 00:11:09.560
and we thought the
midpoint should

00:11:09.560 --> 00:11:11.960
be about the 50th
percentile, that child

00:11:11.960 --> 00:11:13.450
would be short for the family.

00:11:13.450 --> 00:11:17.600
So we always like to take the
family heights into account.

00:11:17.600 --> 00:11:20.200
So number one question,
is the child's short?

00:11:20.200 --> 00:11:22.440
It will depend on what
the height prediction is.

00:11:22.440 --> 00:11:23.130
SAL KHAN: I see.

00:11:23.130 --> 00:11:25.169
So if my son was tracking
down here at the 5%.

00:11:25.169 --> 00:11:27.043
DR. LAURA BACHRACH: That
would be concerning.

00:11:27.043 --> 00:11:28.970
SAL KHAN: Even if he's growing
the two inches every year

00:11:28.970 --> 00:11:30.540
and he's tracking that, it
still would be concerning.

00:11:30.540 --> 00:11:32.050
DR. LAURA BACHRACH: Well, it
would raise some questions

00:11:32.050 --> 00:11:33.100
in our minds.

00:11:33.100 --> 00:11:36.900
But that's the more
important factor is not just

00:11:36.900 --> 00:11:38.860
where they on the
curve at the moment.

00:11:38.860 --> 00:11:40.640
But are they growing
at the normal rate?

00:11:40.640 --> 00:11:43.280
And the child who is not
growing at the normal rate

00:11:43.280 --> 00:11:45.960
raises more red
flags than the child

00:11:45.960 --> 00:11:47.220
who's trotting up the curve.

00:11:47.220 --> 00:11:48.136
SAL KHAN: Fascinating.

00:11:48.136 --> 00:11:50.305
That's interesting, wow.

00:11:50.305 --> 00:11:52.480
DR. LAURA BACHRACH:
So that's the issue.

00:11:52.480 --> 00:11:54.700
And that's what we
approach every day.

00:11:54.700 --> 00:11:57.440
We want to look into
the various causes,

00:11:57.440 --> 00:11:59.280
potentially, for
growth slowdown.

00:11:59.280 --> 00:12:04.130
We want to address treatment
to the specific etiology.

00:12:04.130 --> 00:12:05.675
SAL KHAN: And etiology means--

00:12:05.675 --> 00:12:07.330
DR. LAURA BACHRACH:
Well, for example,

00:12:07.330 --> 00:12:09.800
if the child has a deficiency
of thyroid hormone,

00:12:09.800 --> 00:12:10.870
we want to give
thyroid hormone back.

00:12:10.870 --> 00:12:12.280
SAL KHAN: So etiology
is like the cause.

00:12:12.280 --> 00:12:13.529
DR. LAURA BACHRACH: The cause.

00:12:13.529 --> 00:12:16.230
If the child isn't growing
because he has a nutritional

00:12:16.230 --> 00:12:18.670
problem, like Celiac
Disease, we want

00:12:18.670 --> 00:12:22.170
to put him on a special
diet to address that issue.

00:12:22.170 --> 00:12:24.240
Some parents think,
well, what we

00:12:24.240 --> 00:12:27.050
want to do-- my child is
healthy and normal and growing

00:12:27.050 --> 00:12:29.780
normally, but I want to give
him some growth hormone.

00:12:29.780 --> 00:12:31.550
That becomes a topic in itself.

00:12:31.550 --> 00:12:32.910
SAL KHAN: Right, very good.

00:12:32.910 --> 00:12:33.951
Well, thank you for this.

00:12:33.951 --> 00:12:35.680
This was super informative.


Precocious puberty

WEBVTT
Kind: captions
Language: en

00:00:00.938 --> 00:00:02.421
i'm here at stanford medical school

00:00:02.498 --> 00:00:05.400
with Morgan Theis and Dr. Laura Bachrach

00:00:05.400 --> 00:00:08.867
and they're going to teach us some things.

00:00:08.867 --> 00:00:11.133
Okay, so what are we going to learn about today?

00:00:11.133 --> 00:00:14.067
I'd like to talk about precocious puberty

00:00:14.067 --> 00:00:18.067
it seems to be on the minds of many parents these days

00:00:18.067 --> 00:00:22.267
they worry that their child is developing too early,

00:00:22.267 --> 00:00:26.600
they worry their child is going too small as a result,

00:00:26.600 --> 00:00:29.000
they worry their child is going to get picked on,

00:00:29.000 --> 00:00:31.800
and they worry they might have done something wrong.

00:00:31.800 --> 00:00:35.867
Fed the child the wrong food, or exposed them to the wrong videos,

00:00:35.867 --> 00:00:38.267
to cause this all to happen.

00:00:38.267 --> 00:00:41.800
So could we just talk about what precocious puberty means,

00:00:41.800 --> 00:00:43.800
it almost sounds like they've done something too soon,

00:00:43.800 --> 00:00:45.733
is that correct?

00:00:45.733 --> 00:00:47.667
It's exactly true.

00:00:47.667 --> 00:00:51.800
The normal process of puberty, in a girl, we think,

00:00:51.800 --> 00:00:56.067
we used to think, started around the aged of 10,

00:00:56.067 --> 00:00:58.600
with a little bit of breast development.

00:00:58.600 --> 00:01:01.667
And around 6 months later, the girls would get

00:01:01.667 --> 00:01:03.667
a little bit of pubic hair,

00:01:03.667 --> 00:01:06.014
and around the age of 12 and 3/4 to 13

00:01:06.014 --> 00:01:08.429
they'd get their first period.

00:01:08.429 --> 00:01:10.751
Ok.

00:01:10.751 --> 00:01:13.400
In boys, we used to think,

00:01:13.400 --> 00:01:15.733
the process was starting a little later,

00:01:15.733 --> 00:01:18.267
at about 11 and a half.

00:01:18.267 --> 00:01:20.933
The boys would get some enlargement of the testes.

00:01:20.933 --> 00:01:24.467
They'd get some pubic hair about a year later.

00:01:24.467 --> 00:01:28.000
And by age 15 or so, they'd be mature.

00:01:28.000 --> 00:01:33.267
We have a definition of what's precocious,

00:01:33.267 --> 00:01:37.533
uh, when there's signs of puberty before 8, in a girl,

00:01:37.533 --> 00:01:41.933
or before 9, in a boy.

00:01:41.933 --> 00:01:48.133
Ok. So, 8 or less in a girl, would be precocious,

00:01:48.133 --> 00:01:50.467
and that's for the breast development?

00:01:50.467 --> 00:01:52.400
For any signs of puberty:

00:01:52.400 --> 00:01:56.000
the breasts, the pubic hair or the period

00:01:56.000 --> 00:01:59.800
would be precocious if it happened before the age of 8 in a girl.

00:01:59.800 --> 00:02:07.467
And in a boy, before the age of 9.

00:02:07.467 --> 00:02:10.867
Now this has become a little bit controversial

00:02:10.867 --> 00:02:15.067
because there was one very large pediatric study

00:02:15.067 --> 00:02:19.333
that involved over 17 000 girls

00:02:19.333 --> 00:02:24.200
that found that as many as 25% of african american

00:02:24.200 --> 00:02:28.133
girls would have sign of puberty before 8,

00:02:28.133 --> 00:02:31.600
and as many 7% of the white girls had some

00:02:31.600 --> 00:02:34.533
signs of puberty before age 8.

00:02:34.533 --> 00:02:37.333
But we're still basically using these guidelines.

00:02:37.333 --> 00:02:40.933
Not to say that this is definetely abnormal, but

00:02:40.933 --> 00:02:43.267
this is something we're going to evaluate.

00:02:43.267 --> 00:02:46.267
If we see signs of puberty before those age landmarks.

00:02:46.267 --> 00:02:48.200
Ok, so it sounds like there's a lot of variability,

00:02:48.200 --> 00:02:50.667
it's kind of hard to know in any individual case,

00:02:50.667 --> 00:02:52.933
whether it's normal or not, but we have to have

00:02:52.933 --> 00:02:55.200
some kind of threshold for which we're going to

00:02:55.200 --> 00:02:57.533
work someone up to make sure everything is normal.

00:02:57.533 --> 00:02:59.800
You hit on a really important word.

00:02:59.800 --> 00:03:01.800
And that is variability.

00:03:01.800 --> 00:03:05.400
And a lot of this variability, uh, is determined by genetics.

00:03:05.400 --> 00:03:09.867
So part of what we always need to know is

00:03:09.867 --> 00:03:13.133
the timing of development in the family.

00:03:13.133 --> 00:03:16.267
So when did mom get her first menstrual period,

00:03:16.267 --> 00:03:20.200
when did dad get his puberty and growth spurt?

00:03:20.200 --> 00:03:22.800
So that's part of it, genetics,

00:03:22.800 --> 00:03:25.000
and we need to know that, take that into account:

00:03:25.000 --> 00:03:27.600
If mom had her first period at 10 and started

00:03:27.600 --> 00:03:29.133
her breasts at 8

00:03:29.133 --> 00:03:30.800
it might be perfectly normal for her daugher.

00:03:30.800 --> 00:03:33.133
If mom's period were at 14 and her daughter has

00:03:33.133 --> 00:03:35.133
breast development at 7 and a half

00:03:35.133 --> 00:03:36.200
it's more worrysome.

00:03:36.200 --> 00:03:37.200
Ok.

00:03:37.200 --> 00:03:39.800
Ok, the second factor that seems to be contributing,

00:03:39.800 --> 00:03:40.600
potentially,

00:03:40.600 --> 00:03:42.867
is the overnutrition of our young people.

00:03:42.867 --> 00:03:44.867
Oh, yes.

00:03:44.867 --> 00:03:47.600
And in the particular study that I mentioned to you,

00:03:47.600 --> 00:03:50.400
where they looked at over 17 000 children,

00:03:50.400 --> 00:03:53.400
at least for the white population,

00:03:53.400 --> 00:03:56.267
the could explain the earlier signs of puberty

00:03:56.267 --> 00:04:00.400
as an association with a high body mass index.

00:04:00.400 --> 00:04:03.733
So it looked as if, if you overnourish your child

00:04:03.733 --> 00:04:06.267
you may speed along their growth, and eventually,

00:04:06.267 --> 00:04:09.200
potentially, speed along the onset

00:04:09.200 --> 00:04:10.800
of puberty.

00:04:10.800 --> 00:04:14.067
Now, this did not hold up as an association in the

00:04:14.067 --> 00:04:16.533
african american population, so there's other factors

00:04:16.533 --> 00:04:18.267
going on there.

00:04:18.267 --> 00:04:20.333
But that's something that we rtake into account.

00:04:20.333 --> 00:04:22.800
THe bottom line is,

00:04:22.800 --> 00:04:26.533
the child may present with some signs of early puberty,

00:04:26.533 --> 00:04:29.267
mom or dad get worried,

00:04:29.267 --> 00:04:31.200
they go to the pediatrician,

00:04:31.200 --> 00:04:34.200
and the pediatrician has to decide what's going on.

00:04:34.200 --> 00:04:37.800
Ok, now, JUST Backing up a little bit, is this a problem?

00:04:37.800 --> 00:04:40.133
I mean, what's the problem with, say, a 7 year old girl

00:04:40.133 --> 00:04:45.867
starting puberty, or, uh, an 8 year old boy

00:04:45.867 --> 00:04:47.667
starting puberty early?

00:04:47.667 --> 00:04:48.933
I imagine there could be some social implications

00:04:48.933 --> 00:04:49.933
(as you mentionened)

00:04:49.933 --> 00:04:51.667
but what are sort of the things

00:04:51.667 --> 00:04:52.733
we worry about?

00:04:52.733 --> 00:04:54.667
Well, that's an important question,

00:04:54.667 --> 00:04:55.933
because it comes up not only how far do we go to

00:04:55.933 --> 00:04:57.800
evaluate them, but how far do we go

00:04:57.800 --> 00:04:59.800
to treat them?

00:04:59.800 --> 00:05:01.467
So, one of the concerns parents have,

00:05:01.467 --> 00:05:04.267
relates to their final height.

00:05:04.267 --> 00:05:07.800
So, if they start their growth spurt early in life,

00:05:07.800 --> 00:05:10.533
and close it off early in life,

00:05:10.533 --> 00:05:11.867
are them gonna cheat themselves

00:05:11.867 --> 00:05:13.933
out of some final height?

00:05:13.933 --> 00:05:14.533
Right.

00:05:14.533 --> 00:05:16.133
So height is a concern.

00:05:16.133 --> 00:05:20.067
And its impact really depends upon how young the child is.

00:05:20.067 --> 00:05:21.533
A three year old going into puberty

00:05:21.533 --> 00:05:23.400
is definetely going to end up short

00:05:23.400 --> 00:05:24.533
if we don't do something.

00:05:24.533 --> 00:05:26.400
A seven and a half old girl is

00:05:26.400 --> 00:05:29.400
probably not going to be altered by this

00:05:29.400 --> 00:05:31.467
in terms of height.

00:05:31.467 --> 00:05:33.200
The second concern is definetely what you

00:05:33.200 --> 00:05:34.867
brought up, in terms of social concern.

00:05:34.867 --> 00:05:39.733
Parents worry their child may behave in an older way,

00:05:39.733 --> 00:05:42.400
or be treat in a way that

00:05:42.400 --> 00:05:44.000
they're not quite ready for.

00:05:44.000 --> 00:05:46.933
They mey get unwarranted attention

00:05:46.933 --> 00:05:49.333
from people because they look older.

00:05:49.333 --> 00:05:51.800
And there is even potential concern for abuse,

00:05:51.800 --> 00:05:53.133
sexual abuse.

00:05:53.133 --> 00:05:53.633
Um, right.

00:05:53.633 --> 00:05:55.600
So those are the usual parental concerns

00:05:55.600 --> 00:05:57.800
for why they bring the child in.

00:05:57.800 --> 00:06:00.667
The other concern they have is, often

00:06:00.667 --> 00:06:02.467
"what am I doing wrong".

00:06:02.467 --> 00:06:02.967
There are a lot of questions about

00:06:02.967 --> 00:06:05.733
"should I have fed my child organic food?"

00:06:05.733 --> 00:06:07.933
"what about the soap i was using?"

00:06:07.933 --> 00:06:10.733
"what about the soap operas my child was watching?"

00:06:10.733 --> 00:06:11.667
You know, they're really

00:06:11.667 --> 00:06:13.933
concerned about something they might have done.

00:06:13.933 --> 00:06:16.667
And they worry about these additives in ourplastics,

00:06:16.667 --> 00:06:18.267
in our theeth sealants, etc...

00:06:18.267 --> 00:06:21.467
They worry about evils inour environment.

00:06:21.467 --> 00:06:22.133
Okay.

00:06:22.133 --> 00:06:25.267
So things that you address in the visit that

00:06:25.267 --> 00:06:26.400
you have with them are definetely

00:06:26.400 --> 00:06:29.667
some of the, the concerns that parent have

00:06:29.667 --> 00:06:31.933
about what they could have done differently.

00:06:31.933 --> 00:06:34.800
Exactly. We start out, assessing

00:06:34.800 --> 00:06:37.200
in a sort of a systematic way.

00:06:37.200 --> 00:06:38.867
The first question we want to know, is

00:06:38.867 --> 00:06:40.533
when did this all start?

00:06:40.533 --> 00:06:42.333
And what did they notice.

00:06:42.333 --> 00:06:43.600
And it's really important

00:06:43.600 --> 00:06:45.600
to break down the signs of puberty,

00:06:45.600 --> 00:06:47.667
because different hormones contribute to

00:06:47.667 --> 00:06:49.267
the different signs.

00:06:49.267 --> 00:06:51.533
For example, in a girl, if she is presenting with

00:06:51.533 --> 00:06:55.400
some body odor, some acne, and some pubic hair,

00:06:55.400 --> 00:06:57.800
but no signs of any breast development,

00:06:57.800 --> 00:07:00.333
that leads us down the road to

00:07:00.333 --> 00:07:02.200
worry about what we call her androgens

00:07:02.200 --> 00:07:03.333
or her male hormones.

00:07:03.333 --> 00:07:06.800
If a girl comes in with just breast development

00:07:06.800 --> 00:07:09.732
but none of the body hair

00:07:09.732 --> 00:07:11.933
or body odor, we think, aha! she's been

00:07:11.933 --> 00:07:13.800
exposed to estrogens.

00:07:13.800 --> 00:07:15.667
And so we get a lot from the physical exam in

00:07:15.667 --> 00:07:18.800
terms of thinking what hormones to go after.

00:07:18.800 --> 00:07:21.200
okay, so even though the definitions of precocious

00:07:21.200 --> 00:07:23.200
is just any of these

00:07:23.200 --> 00:07:26.467
different physical developments happening

00:07:26.467 --> 00:07:27.933
too soon, the combination that you see

00:07:27.933 --> 00:07:29.733
is going to direct what yo uthing is going on

00:07:29.733 --> 00:07:31.600
wit hthem clinically.

00:07:31.600 --> 00:07:32.400
Exactly.

00:07:32.400 --> 00:07:33.000
Ok

00:07:33.000 --> 00:07:34.733
It will make us more or less worried

00:07:34.733 --> 00:07:38.133
and it will take us down one avenue or another,

00:07:38.133 --> 00:07:41.267
thinking about what could be wrong,

00:07:41.267 --> 00:07:44.800
what level of abnormality in the hormone system is at work.

00:07:44.800 --> 00:07:48.200
Ok. Can I ask you a question, just curious, so

00:07:48.200 --> 00:07:51.667
what are the most common diagnosis given

00:07:51.667 --> 00:07:54.133
to people coming in with their kids, that are

00:07:54.133 --> 00:07:56.067
concerned for precocious puberty?

00:07:56.067 --> 00:07:58.467
The common diagnosis, is "variations are normal".

00:07:58.467 --> 00:08:00.800
Aha.

00:08:00.800 --> 00:08:05.333
There is a condition called

00:08:05.333 --> 00:08:07.800
"isolated premature adrenarche" which is a

00:08:07.800 --> 00:08:09.800
fancy doctor way of saying

00:08:09.800 --> 00:08:13.533
the adrenal glands producting their

00:08:13.533 --> 00:08:16.600
hormones, we see pubic hair, underarm hair, and acne.

00:08:16.600 --> 00:08:19.333
Uh... We also can see isolated

00:08:19.333 --> 00:08:21.800
breast development in little toddler girls

00:08:21.800 --> 00:08:23.333
that's not concerning.

00:08:23.333 --> 00:08:25.467
So that would just go away, or?

00:08:25.467 --> 00:08:27.667
Yes. Typically that begins between

00:08:27.667 --> 00:08:29.000
six months and two years and

00:08:29.000 --> 00:08:29.800
goes away.

00:08:29.800 --> 00:08:33.667
But even within the more full blown cases,

00:08:33.667 --> 00:08:37.200
where we're seeing breast and the pubic hair

00:08:37.200 --> 00:08:39.667
in a girl, or the enlagrement of the testes

00:08:39.667 --> 00:08:43.200
and the pubic hair in a boy, where's it's full on,

00:08:43.200 --> 00:08:48.067
full blown puberty, it may be idiopathic,

00:08:48.067 --> 00:08:49.800
or not pathological.

00:08:49.800 --> 00:08:51.267
We think that in girls,

00:08:51.267 --> 00:08:57.267
who develop fully, 95% of the time, even if they

00:08:57.267 --> 00:09:00.133
have the full blown puberty,

00:09:00.133 --> 00:09:02.733
it's idiopathic, or not pathological.

00:09:02.733 --> 00:09:06.400
Whereas in boys, about 50% of the time, there is pathology.

00:09:06.400 --> 00:09:10.133
So the condition is less common on boys, but

00:09:10.133 --> 00:09:12.133
when it occurs in boys, it's more worrisome.

00:09:12.133 --> 00:09:12.867
Oh, interesting.

00:09:12.867 --> 00:09:17.600
So it's less common for boys to have any signs of

00:09:17.600 --> 00:09:19.467
precocious puberty, but when it does happen you worry more.

00:09:19.467 --> 00:09:21.333
Exactly.

00:09:21.333 --> 00:09:23.733
Because it's more likeyl to be something bad.

00:09:23.733 --> 00:09:24.267
Exactly.

00:09:24.267 --> 00:09:24.867
Ok.

00:09:24.867 --> 00:09:30.667
So I'm guessing as an endocrinologist,

00:09:30.667 --> 00:09:34.467
once you've sort of ruled out the normal things, then you start th

00:09:34.467 --> 00:09:36.200
then you start thinking more about

00:09:36.200 --> 00:09:38.600
sort of what's going on in terms of all the

00:09:38.600 --> 00:09:39.800
different hormones that are controlling the

00:09:39.800 --> 00:09:40.300
se

00:09:40.300 --> 00:09:41.800
things, which maybe is something that

00:09:41.800 --> 00:09:43.533
we'll talk about in a different

00:09:43.533 --> 00:09:44.600
lecture

00:09:44.600 --> 00:09:45.400
exactly.

00:09:45.400 --> 00:09:47.000
is there any other sort of general things

00:09:47.000 --> 00:09:48.600
that you wanted to adress when

00:09:48.600 --> 00:09:50.533
we'll just talking about...

00:09:50.533 --> 00:09:52.867
I think the general advice I would give to a parent

00:09:52.867 --> 00:09:56.800
if see signs of puberty in their child,

00:09:56.800 --> 00:09:59.933
before 8 in a girl, before 9 in a boy,

00:09:59.933 --> 00:10:02.867
they should at least question their pediatrician

00:10:02.867 --> 00:10:05.867
about it, uh, and the pediatrician should do

00:10:05.867 --> 00:10:07.667
a complete exam, and the

00:10:07.667 --> 00:10:10.400
other factor that needs to be looked at carefully is growth,

00:10:10.400 --> 00:10:14.200
because a child who is truly in puberty will have a growth spurt.

00:10:14.200 --> 00:10:17.267
So, those are things that parents can be

00:10:17.267 --> 00:10:17.800
aware of at home, but I think it's

00:10:17.800 --> 00:10:21.400
important that the parent asks the pediatrician about it,

00:10:21.400 --> 00:10:23.400
if they are concerned.

00:10:23.400 --> 99:59:59.999
Ok, well thank you so much.


Bacterial meningitis

WEBVTT
Kind: captions
Language: en

00:00:00.580 --> 00:00:03.410
SAL KHAN: We're here at Stanford
Medical School with fourth year

00:00:03.410 --> 00:00:07.812
medical student Morgan Theis
and Dr. Charles Prober.

00:00:07.812 --> 00:00:09.520
MORGAN THEIS: OK, Dr.
Prober, what are we

00:00:09.520 --> 00:00:11.020
going to talk about today?

00:00:11.020 --> 00:00:12.686
DR. CHARLES PROBER:
So Morgan, I thought

00:00:12.686 --> 00:00:16.050
we'd talk about bacterial
meningitis in children.

00:00:16.050 --> 00:00:17.929
MORGAN THEIS: OK.

00:00:17.929 --> 00:00:19.470
DR. CHARLES PROBER:
And what I'd like

00:00:19.470 --> 00:00:22.200
to do, in reflecting
on bacterial meningitis

00:00:22.200 --> 00:00:27.140
is go back to some lessons
that we learned in "The Prudent

00:00:27.140 --> 00:00:32.420
Prescribing of
Antibiotics," a prior video.

00:00:32.420 --> 00:00:34.960
And one of the things
that was mentioned

00:00:34.960 --> 00:00:38.670
as a general principle
in that particular video

00:00:38.670 --> 00:00:44.100
was trying to understand
where the site of infection

00:00:44.100 --> 00:00:48.380
is in a child, in order to
pick the right antibiotics

00:00:48.380 --> 00:00:50.390
and the right management.

00:00:50.390 --> 00:00:52.780
So in this case,
because I'm referring

00:00:52.780 --> 00:00:55.570
to bacterial meningitis,
a question might be,

00:00:55.570 --> 00:00:59.940
what would make you think that a
child has bacterial meningitis?

00:00:59.940 --> 00:01:02.620
That is, what are the
signs and symptoms

00:01:02.620 --> 00:01:04.539
of bacterial meningitis?

00:01:04.539 --> 00:01:06.970
MORGAN THEIS: So this is kind
of thinking about the site,

00:01:06.970 --> 00:01:08.344
knowing that
there's an infection

00:01:08.344 --> 00:01:10.730
in the cerebrospinal
fluid or fluid

00:01:10.730 --> 00:01:12.800
around the brain
and spinal cord.

00:01:12.800 --> 00:01:15.544
You have to look for that in a
variety of ways, as a doctor.

00:01:15.544 --> 00:01:16.710
DR. CHARLES PROBER: Exactly.

00:01:16.710 --> 00:01:21.610
And one of the things which
will make a physician suspicious

00:01:21.610 --> 00:01:25.040
that there may be an infection
in the cerebrospinal fluid

00:01:25.040 --> 00:01:27.290
or that is, in the
central nervous system

00:01:27.290 --> 00:01:29.790
is, a child may not
be behaving normally.

00:01:29.790 --> 00:01:33.460
That is, they'll have an
altered state of consciousness.

00:01:33.460 --> 00:01:36.820
They'll be very, very sleepy.

00:01:36.820 --> 00:01:40.536
Or they'll be very irritable.

00:01:40.536 --> 00:01:43.240
MORGAN THEIS: OK, so
I guess I would say,

00:01:43.240 --> 00:01:47.000
the signs here--
irritable children.

00:01:47.000 --> 00:01:48.500
And what was the
other one you said?

00:01:48.500 --> 00:01:49.958
DR. CHARLES PROBER:
And I mentioned

00:01:49.958 --> 00:01:51.200
they might be very sleepy.

00:01:51.200 --> 00:01:53.440
Some people might use
the word lethargic,

00:01:53.440 --> 00:01:56.700
as an altered state
of consciousness.

00:01:56.700 --> 00:02:00.110
And at the extreme of that,
the child would be in a coma.

00:02:00.110 --> 00:02:05.470
But that would be more
advanced in the infection.

00:02:05.470 --> 00:02:08.460
And then, the child
would almost invariably

00:02:08.460 --> 00:02:13.880
have a fever associated
with it, with this illness.

00:02:13.880 --> 00:02:17.740
And on examination, when the
physician examines the child,

00:02:17.740 --> 00:02:21.980
they may detect what are
called meningeal signs.

00:02:21.980 --> 00:02:27.390
And those meningeal signs
include a stiff neck,

00:02:27.390 --> 00:02:30.074
especially if the child is
over one or two years of age.

00:02:30.074 --> 00:02:31.490
MORGAN THEIS: And
how can you tell

00:02:31.490 --> 00:02:32.961
if someone has a stiff neck?

00:02:32.961 --> 00:02:35.210
DR. CHARLES PROBER: So what's
the physician will often

00:02:35.210 --> 00:02:37.950
do is hold the child
behind the head

00:02:37.950 --> 00:02:42.160
and try to flex the head on
the next, try to flex the neck.

00:02:42.160 --> 00:02:44.340
And stiff would
be literally that.

00:02:44.340 --> 00:02:47.130
The child's neck
would not bend, when

00:02:47.130 --> 00:02:49.174
the head is elevated
from the bed.

00:02:49.174 --> 00:02:50.090
MORGAN THEIS: Oh, wow.

00:02:50.090 --> 00:02:52.410
So it just stays really linear.

00:02:52.410 --> 00:02:53.880
You can't really curve it well.

00:02:53.880 --> 00:02:55.150
DR. CHARLES PROBER: Exactly.

00:02:55.150 --> 00:02:58.580
The other meningeal signs that
may be present in addition

00:02:58.580 --> 00:03:00.620
to the stiff neck
are the child may

00:03:00.620 --> 00:03:04.930
have some seizures,
abnormal movements.

00:03:04.930 --> 00:03:09.380
The child might also assume an
abnormal posture, stiffening

00:03:09.380 --> 00:03:11.610
of the body, so not just
the next being stiff

00:03:11.610 --> 00:03:16.130
but the rest of the body
being stiff as well.

00:03:16.130 --> 00:03:19.720
And on examination of
the neurologic system,

00:03:19.720 --> 00:03:21.530
the nervous system,
the child may

00:03:21.530 --> 00:03:23.900
have what are referred
to as focal. signs.

00:03:23.900 --> 00:03:27.960
That is asymmetry between
the two sides of the body.

00:03:27.960 --> 00:03:29.790
MORGAN THEIS: Oh, and
what kind of things

00:03:29.790 --> 00:03:31.440
would you see that
were asymmetrical?

00:03:31.440 --> 00:03:33.990
DR. CHARLES PROBER: It could
be that one side of the body

00:03:33.990 --> 00:03:35.880
is weaker than the other.

00:03:35.880 --> 00:03:37.850
It could be that
one side of the body

00:03:37.850 --> 00:03:41.870
has different reflexes than
the other side of the body.

00:03:41.870 --> 00:03:44.230
So these are all
signs and symptoms

00:03:44.230 --> 00:03:48.520
that may be associated with
bacterial meningitis, that

00:03:48.520 --> 00:03:52.240
would make the physician
suspicious of the diagnosis

00:03:52.240 --> 00:03:53.102
of meningitis.

00:03:53.102 --> 00:03:53.840
MORGAN THEIS: OK.

00:03:53.840 --> 00:03:55.140
So we talked about
some of the things

00:03:55.140 --> 00:03:56.190
you look for as a doctor.

00:03:56.190 --> 00:03:58.320
Now, just going back
a minute, you said,

00:03:58.320 --> 00:04:00.726
we're talking about
bacterial meningitis.

00:04:00.726 --> 00:04:03.100
Does that assume that there
are other types of meningitis

00:04:03.100 --> 00:04:04.790
that we're not addressing
in this lecture?

00:04:04.790 --> 00:04:06.873
DR. CHARLES PROBER: That's
a very important point.

00:04:06.873 --> 00:04:09.730
So I am focusing on
bacterial meningitis.

00:04:09.730 --> 00:04:12.440
There are other types
of organisms, that is,

00:04:12.440 --> 00:04:15.250
non-bacteria that
can cause meningitis.

00:04:15.250 --> 00:04:19.269
And the most prominent of those
other organisms are viruses.

00:04:19.269 --> 00:04:23.220
So you can have a viral
meningitis, sometimes referred

00:04:23.220 --> 00:04:26.710
to as aseptic meningitis.

00:04:26.710 --> 00:04:28.190
And that, in fact,
is more common

00:04:28.190 --> 00:04:29.990
than bacterial meningitis.

00:04:29.990 --> 00:04:32.440
So it's very
important to consider.

00:04:32.440 --> 00:04:36.120
There are also some parasites
that can cause meningitis.

00:04:36.120 --> 00:04:41.190
And there are some fungi
that can cause meningitis.

00:04:41.190 --> 00:04:45.070
The fungi and
parasites are uncommon

00:04:45.070 --> 00:04:47.840
in the general
population, but they

00:04:47.840 --> 00:04:53.260
may occur in patients who have
an abnormal immune system.

00:04:53.260 --> 00:04:55.210
Viral meningitis,
on the other hand,

00:04:55.210 --> 00:04:57.590
is really, as I
mentioned, quite common.

00:04:57.590 --> 00:05:01.660
But for today, I'm focusing
on bacterial meningitis.

00:05:01.660 --> 00:05:04.160
So you suspect that the
infection may be present,

00:05:04.160 --> 00:05:07.530
based upon those signs
and symptoms that we've

00:05:07.530 --> 00:05:08.870
spoken about.

00:05:08.870 --> 00:05:12.050
And then to prove or
determine whether or not

00:05:12.050 --> 00:05:17.570
meningitis is present,
cerebral spinal fluid

00:05:17.570 --> 00:05:19.140
has to be examined.

00:05:19.140 --> 00:05:26.175
And cerebral spinal fluid, which
is typically abbreviated CSF.

00:05:26.175 --> 00:05:30.170
MORGAN THEIS: CSF is
cerebrospinal fluid.

00:05:30.170 --> 00:05:32.120
We already got that but OK.

00:05:32.120 --> 00:05:32.955
Sorry.

00:05:32.955 --> 00:05:34.780
DR. CHARLES PROBER:
And that's obtained

00:05:34.780 --> 00:05:37.810
by doing something called a
lumbar puncture, by putting

00:05:37.810 --> 00:05:41.115
a needle in the back
to obtain fluid.

00:05:41.115 --> 00:05:42.370
MORGAN THEIS: OK.

00:05:42.370 --> 00:05:44.140
Is that also what
a spinal tap is?

00:05:44.140 --> 00:05:46.473
DR. CHARLES PROBER: And that's
also called a spinal tap,

00:05:46.473 --> 00:05:49.140
exactly, a Lumbar
puncture or a spinal tap.

00:05:49.140 --> 00:05:55.820
When that's obtained using a
needle into the lumber area,

00:05:55.820 --> 00:05:58.870
the fluid is then sent
to the laboratory, who

00:05:58.870 --> 00:06:02.490
will examine the fluid
in different ways.

00:06:02.490 --> 00:06:04.890
One is to look
under the microscope

00:06:04.890 --> 00:06:08.150
and determine if there are an
abnormal number of white blood

00:06:08.150 --> 00:06:09.060
cells present.

00:06:09.060 --> 00:06:11.380
MORGAN THEIS: So abnormal
meaning high or low?

00:06:11.380 --> 00:06:12.830
DR. CHARLES PROBER:
Meaning just high actually.

00:06:12.830 --> 00:06:13.450
MORGAN THEIS: OK.

00:06:13.450 --> 00:06:14.991
DR. CHARLES PROBER:
The normal number

00:06:14.991 --> 00:06:17.220
of white blood cells
in the CSF is 0.

00:06:17.220 --> 00:06:19.742
So high is something
greater than 0.

00:06:19.742 --> 00:06:20.450
MORGAN THEIS: OK.

00:06:20.450 --> 00:06:22.533
DR. CHARLES PROBER: And
with bacterial meningitis,

00:06:22.533 --> 00:06:26.210
it tends to be really quite
high, 1,000 or 2,000 or more

00:06:26.210 --> 00:06:27.740
than that.

00:06:27.740 --> 00:06:30.077
With viral meningitis, it
may not be quite as high.

00:06:30.077 --> 00:06:31.660
MORGAN THEIS: And
that's per some unit

00:06:31.660 --> 00:06:33.635
of volume of this fluid.

00:06:33.635 --> 00:06:35.256
DR. CHARLES PROBER: Exactly.

00:06:35.256 --> 00:06:38.360
A glucose concentration
is also measured

00:06:38.360 --> 00:06:40.210
when the fluid is
sent to the lab.

00:06:40.210 --> 00:06:43.670
And with bacterial meningitis,
the glucose in the spinal fluid

00:06:43.670 --> 00:06:47.100
tends to be low, less than 40.

00:06:47.100 --> 00:06:49.015
MORGAN THEIS: Now,
why would it be low?

00:06:49.015 --> 00:06:52.410
DR. CHARLES PROBER: It's low
because with meningitis, you

00:06:52.410 --> 00:06:58.090
have an abnormal penetrability
or lack of penetrability

00:06:58.090 --> 00:07:00.839
of the meninges, which are
the coverings of the brain,

00:07:00.839 --> 00:07:02.380
reducing the amount
of glucose that's

00:07:02.380 --> 00:07:05.340
transported into
the spinal fluid.

00:07:05.340 --> 00:07:08.110
And then, most
importantly, the fluid

00:07:08.110 --> 00:07:09.600
is examined with
something called

00:07:09.600 --> 00:07:12.410
a Gram stain, a
special kind of stain.

00:07:12.410 --> 00:07:17.600
It's Gram with a capital
G, named after Dr. Gram.

00:07:17.600 --> 00:07:21.000
And a Gram stain can
determine whether or not

00:07:21.000 --> 00:07:23.754
there are bacteria present.

00:07:23.754 --> 00:07:24.740
MORGAN THEIS: OK.

00:07:24.740 --> 00:07:26.135
So you're actually
staining the bacteria.

00:07:26.135 --> 00:07:27.301
DR. CHARLES PROBER: Exactly.

00:07:27.301 --> 00:07:29.630
And if there are sufficient
bacteria present,

00:07:29.630 --> 00:07:33.600
the Gram stain will
reveal those bacteria.

00:07:33.600 --> 00:07:36.690
And so with
bacterial meningitis,

00:07:36.690 --> 00:07:40.810
the second prudent principle
is to know the usual pathogens.

00:07:40.810 --> 00:07:43.240
So if a spinal
fluid is obtained,

00:07:43.240 --> 00:07:46.840
there are lots of white
cells, the glucose is low.

00:07:46.840 --> 00:07:49.080
Even with a negative
Gram stain, one

00:07:49.080 --> 00:07:51.440
can guess the usual
pathogens, because the list

00:07:51.440 --> 00:07:53.880
is short in normal children.

00:07:53.880 --> 00:07:57.810
And those bacteria, the short
list includes a bacteria

00:07:57.810 --> 00:08:05.860
called Haemophilus
influenzae, type B.

00:08:05.860 --> 00:08:07.510
MORGAN THEIS: Is
there an A on that?

00:08:07.510 --> 00:08:08.510
I mean, an E at the end?

00:08:08.510 --> 00:08:10.720
DR. CHARLES PROBER:
There is an E on the end.

00:08:10.720 --> 00:08:14.590
A second bacteria is
the new pnuemococcus.

00:08:14.590 --> 00:08:16.030
MORGAN THEIS: Now, that's funny.

00:08:16.030 --> 00:08:17.680
It sounds like it
causes pneumonia.

00:08:17.680 --> 00:08:20.305
DR. CHARLES PROBER: And it does
indeed cause pneumonia as well.

00:08:20.305 --> 00:08:22.440
But it also causes
bacterial meningitis.

00:08:22.440 --> 00:08:24.470
And a third bacteria is
called meningicoccus.

00:08:28.680 --> 00:08:32.030
And those are the
prominent bacteria

00:08:32.030 --> 00:08:35.880
in normal children with
bacterial meningitis.

00:08:35.880 --> 00:08:37.510
The reason though,
we're not seen

00:08:37.510 --> 00:08:41.929
as much bacterial meningitis
in 2011 as we were seeing 10

00:08:41.929 --> 00:08:45.450
and 20 years ago is,
we now have vaccination

00:08:45.450 --> 00:08:48.105
against each of those
three different pathogens.

00:08:48.105 --> 00:08:49.415
MORGAN THEIS: All of them?

00:08:49.415 --> 00:08:50.498
DR. CHARLES PROBER: We do.

00:08:50.498 --> 00:08:54.150
We vaccinate against
Haemophilus influenzae, type B,

00:08:54.150 --> 00:08:56.561
starting at two months of age.

00:08:56.561 --> 00:08:59.580
And by the time the child
is about a year and a half,

00:08:59.580 --> 00:09:01.640
they're completely
protected against

00:09:01.640 --> 00:09:04.470
that particular bacteria.

00:09:04.470 --> 00:09:07.270
The pneumococcus, we
also vaccinate against.

00:09:07.270 --> 00:09:08.452
And it's very successful.

00:09:08.452 --> 00:09:11.310
The vaccine is very
successful at reducing

00:09:11.310 --> 00:09:13.370
the frequency of
pneumococcal meningitis.

00:09:13.370 --> 00:09:16.740
It also starts at
two months of age.

00:09:16.740 --> 00:09:21.380
And meningicoccus, the
vaccine is relatively new

00:09:21.380 --> 00:09:23.310
and is used in children
who are a bit older.

00:09:23.310 --> 00:09:27.950
They're over two years of age,
under special circumstances.

00:09:27.950 --> 00:09:30.570
So that means that
we still can see,

00:09:30.570 --> 00:09:33.720
and do see, cases of
meningicoccal meningitis,

00:09:33.720 --> 00:09:36.255
because it occurs in children
under two years of age.

00:09:36.255 --> 00:09:37.130
MORGAN THEIS: I see.

00:09:37.130 --> 00:09:38.530
DR. CHARLES PROBER: But those
are the usual pathogens.

00:09:38.530 --> 00:09:40.790
And when you go to other
parts of the world who

00:09:40.790 --> 00:09:43.560
don't use vaccines,
those are the pathogens

00:09:43.560 --> 00:09:47.910
that will be prominent in
causing bacterial meningitis.

00:09:47.910 --> 00:09:51.380
And knowing those pathogens,
we go to the third principle

00:09:51.380 --> 00:09:56.470
of antibiotic prescribing, which
is knowing what antibiotics

00:09:56.470 --> 00:09:58.310
typically kill those bacteria.

00:09:58.310 --> 00:09:59.030
MORGAN THEIS: OK.

00:09:59.030 --> 00:10:01.974
So what should I call that
category, like matching?

00:10:01.974 --> 00:10:03.890
DR. CHARLES PROBER:
That's called the pathogen

00:10:03.890 --> 00:10:07.120
sensitivity, knowing
what antibiotics

00:10:07.120 --> 00:10:09.374
work against the likely bug,
so pathogen sensitivity.

00:10:09.374 --> 00:10:11.290
MORGAN THEIS: Pathogen
sensitivity, OK, great.

00:10:11.290 --> 00:10:13.695
DR. CHARLES PROBER:
Sensitivity to the antibiotics.

00:10:13.695 --> 00:10:16.120
MORGAN THEIS: And I think
you were mentioning in you

00:10:16.120 --> 00:10:20.840
last lecture, that varies
by the location in the body

00:10:20.840 --> 00:10:23.235
and the location in
the world that you're

00:10:23.235 --> 00:10:24.110
using the antibiotic.

00:10:24.110 --> 00:10:24.350
Is that right?

00:10:24.350 --> 00:10:25.660
DR. CHARLES PROBER:
It varies according

00:10:25.660 --> 00:10:26.924
to the location in the world.

00:10:26.924 --> 00:10:28.340
MORGAN THEIS: But
not in the body.

00:10:28.340 --> 00:10:30.839
DR. CHARLES PROBER: Not in what
part of the body they're in.

00:10:30.839 --> 00:10:32.720
And fortunately,
for the treatment

00:10:32.720 --> 00:10:35.100
of bacterial meningitis,
to cover all three

00:10:35.100 --> 00:10:39.080
of the bacteria that are
on the list of pathogens,

00:10:39.080 --> 00:10:41.370
two antibiotics cover
all three of them.

00:10:41.370 --> 00:10:44.990
And I'll just mention
their names as I end this.

00:10:44.990 --> 00:10:46.735
One antibiotic is cefotaxime.

00:10:49.650 --> 00:10:52.955
And a reasonable facsimile
of cefotaxime is ceftriaxone.

00:10:52.955 --> 00:10:54.330
They're very
similar antibiotics.

00:10:54.330 --> 00:10:56.816
So we give one or the other
of those two antibiotics.

00:11:00.150 --> 00:11:02.720
And because some of
the new pneumococci

00:11:02.720 --> 00:11:06.915
are resistant to so-called
beta lactam drugs, penicillin

00:11:06.915 --> 00:11:10.000
and cephalosporins,
vancomycin also

00:11:10.000 --> 00:11:16.220
is used to initiate therapy for
suspected bacterial meningitis.

00:11:16.220 --> 00:11:16.970
MORGAN THEIS: OK.

00:11:16.970 --> 00:11:18.840
So we use vancomycin
if we think you

00:11:18.840 --> 00:11:20.810
have sort of
resistant bugs, bugs

00:11:20.810 --> 00:11:23.840
that are resistant to the first
two antibiotics you mentioned.

00:11:23.840 --> 00:11:24.490
DR. CHARLES PROBER: Exactly.

00:11:24.490 --> 00:11:25.680
MORGAN THEIS: And there's
some kind of lab tests

00:11:25.680 --> 00:11:27.470
you might be able to
do to find that out.

00:11:27.470 --> 00:11:28.636
DR. CHARLES PROBER: Exactly.

00:11:28.636 --> 00:11:31.590
So those are the principles
of antibiotic prescribing,

00:11:31.590 --> 00:11:35.280
in terms of the diagnosis
of bacterial meningitis--

00:11:35.280 --> 00:11:37.110
knowing the site
of infection-- that

00:11:37.110 --> 00:11:40.090
is, the spinal fluid--
knowing how to diagnose it,

00:11:40.090 --> 00:11:42.910
what the pathogens, and
what antibiotics wold work

00:11:42.910 --> 00:11:45.272
against those pathogens
at that site of infection.

00:11:45.272 --> 00:11:45.980
MORGAN THEIS: OK.

00:11:45.980 --> 00:11:48.020
And just my last
question is, just

00:11:48.020 --> 00:11:50.540
because we've learned
a lot about how there

00:11:50.540 --> 00:11:53.160
is a tight barrier
between the blood

00:11:53.160 --> 00:11:56.440
and the cerebrospinal
fluid, are these antibiotics

00:11:56.440 --> 00:11:59.350
that you've listed here-- are
those able to sort of penetrate

00:11:59.350 --> 00:12:01.890
through that barrier and get
into the cerebrospinal fluid?

00:12:01.890 --> 00:12:03.890
DR. CHARLES PROBER: An
extraordinarily important

00:12:03.890 --> 00:12:06.820
question, which got to another
principle of antibiotics, which

00:12:06.820 --> 00:12:09.100
is, you have to make sure
they can be delivered

00:12:09.100 --> 00:12:11.610
to the suspected
site of infection.

00:12:11.610 --> 00:12:13.420
And for those
particular antibiotics,

00:12:13.420 --> 00:12:14.385
the answer is, yes.

00:12:14.385 --> 00:12:15.240
MORGAN THEIS: OK.

00:12:15.240 --> 00:12:17.180
Thank you so much.


2011 Calculus BC free response #1d

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:05.533
Part d: Find the total distance traveled by the particle over the time interval between

00:00:05.533 --> 00:00:11.159
time t = 0 and t = 3, or 0 <= t <= 3.

00:00:11.159 --> 00:00:14.267
So let's draw some axes here to just make sure

00:00:14.267 --> 00:00:18.462
and you wouldn't obviously have to do this if you were doing it under time pressure during the actual

00:00:18.462 --> 00:00:23.185
AP exam but my point here to make sure we all are understanding what's going on.

00:00:23.185 --> 00:00:25.867
So when t = 0, where are we?

00:00:25.867 --> 00:00:29.129
Well they tell us; x(0) is 0 so x is 0

00:00:29.129 --> 00:00:35.298
and y(0) is -4 so we're at the point (0, -4).

00:00:35.298 --> 00:00:42.913
That's when t = 0 and in the last problem we figured out what happens when t = 3;

00:00:42.913 --> 00:00:45.133
we figured out that x is at 21.

00:00:45.133 --> 00:00:48.600
I'll just say that's 21 right over there.

00:00:48.600 --> 00:00:54.221
x(3) is 21 and y(3) was like -3 point something,

00:00:54.221 --> 00:00:57.287
so that puts us right over here.

00:00:57.287 --> 00:01:04.708
So this is 21 and we figured this out in the last problem, I think it was -3.226,

00:01:04.708 --> 00:01:07.800
and so this is what happens when t = 3.

00:01:07.800 --> 00:01:10.482
And between these point who knows what the path is.

00:01:10.482 --> 00:01:16.267
We could plot it if we wanted but it might look something like this, so who knows what it does, and we go like that.

00:01:16.267 --> 00:01:21.246
And so in are part d right here they're asking us "What is the total distance traveled?",

00:01:21.246 --> 00:01:28.267
or another way to think about it is "What is the length of this path?"

00:01:28.267 --> 00:01:35.000
And we could, there is a formula for arc length and if you know it, you could just apply it.

00:01:35.000 --> 00:01:39.508
It's not a bad thing to know going into the AP exam, especially under time pressure,

00:01:39.508 --> 00:01:43.010
but I always forget what it is, I'm almost 35 now,

00:01:43.010 --> 00:01:46.852
so I always like to re-derive it and there's always something a little bit satisfying about

00:01:46.852 --> 00:01:52.031
that too because we remind ourselves why the formula works.

00:01:52.031 --> 00:01:56.533
Well how do we figure a little bit of that arc length?

00:01:56.533 --> 00:01:59.687
So actually let me do a little other part; I like this part more.

00:01:59.687 --> 00:02:03.969
So let's say, "How do we figure out a little bit of that arc length right over there?"

00:02:03.969 --> 00:02:07.538
So let's say you have a little bit of that arc length that...

00:02:07.538 --> 00:02:09.918
I'm going to zoom in on that.

00:02:09.918 --> 00:02:18.600
Well you have a little bit of a small change in x over that arc length that I've blown up,

00:02:18.600 --> 00:02:26.379
so call that dx, and you have a small change in y as well, dy,

00:02:26.379 --> 00:02:29.631
and we know from the Pythagorean theorem,

00:02:29.631 --> 00:02:32.662
if we get small enough you can approximate this as just the hypotenuse

00:02:32.662 --> 00:02:36.000
as this is the base, this is the height, and this is the hypotenuse.

00:02:36.000 --> 00:02:41.933
And so this is going to be, especially if you get these small enough, a line is going to be a pretty -

00:02:41.933 --> 00:02:47.985
you could really approximate this arc by the hypotenuse

00:02:47.985 --> 00:02:51.769
right over here.

00:02:51.769 --> 00:02:53.031
We know what this is from the Pythagorean theorem.

00:02:53.031 --> 00:02:59.298
This is going to be the square root of dx squared plus dy squared,

00:02:59.298 --> 00:03:02.157
straight up from the Pythagorean theorem.

00:03:02.157 --> 00:03:05.415
Now, how do we write these as functions of t?

00:03:05.415 --> 00:03:14.067
Well we know that dx/dt is equal to x'(t)

00:03:14.067 --> 00:03:18.590
or if we treat differentials kind of like numbers, and you can most of the time, this is not very rigorous,

00:03:18.590 --> 00:03:29.185
but you that that dx is equal to x'(t) dt and we know that dy of t or dy/dt,

00:03:29.185 --> 00:03:32.677
we know this is the same thing at the derivative of y with respect to t;

00:03:32.677 --> 00:03:39.754
y'(t) multiply both sides by dt you get dy = y'(t) dt.

00:03:39.754 --> 00:03:45.154
And all I'm doing here is essentially reproving or re-deriving the arc length formula.

00:03:45.154 --> 00:03:55.418
So we know that this right over here is just a small little arc length so we could call that dL or da for small arc length.

00:03:55.418 --> 00:03:58.682
Or actually we don't have to worry about what we call that right now.

00:03:58.682 --> 00:04:02.298
But this expression for that very little small arc length right over there;

00:04:02.298 --> 00:04:08.529
if I rewrite it in terms of this and this, what I have on the right-hand side,

00:04:08.529 --> 00:04:10.825
and I want to do that so that I can get everything in terms of t,

00:04:10.825 --> 00:04:15.890
I get it is equal to the square root of dx squared...

00:04:15.890 --> 00:04:25.052
Well dx squared is the same thing as (I'll do it in that magenta color) x'(t) dt squared

00:04:25.052 --> 00:04:37.682
and then you have plus dy squared, and dy squared is just this stuff: y'(t) dt squared.

00:04:37.682 --> 00:04:45.529
And so this little arc length is this right over here, and then you can actually factor out a dt squared,

00:04:45.529 --> 00:05:03.369
so this is going to be equal to dt squared times x'(t) squared plus (I'll do this in green) y'(t) squared.

00:05:03.369 --> 00:05:07.067
And then of course you can factor out the dt out of the radical sign now.

00:05:07.067 --> 00:05:09.805
The square root of dt squared is just dt

00:05:09.805 --> 00:05:14.638
so all of this simplifies to (I'll write it in yellow)

00:05:14.638 --> 00:05:20.041
this part right over here is x'(t) squared

00:05:20.041 --> 00:05:24.766
and this part right over here is y'(t) squared,

00:05:24.766 --> 00:05:28.291
and then we factor out the dt.

00:05:28.291 --> 00:05:34.723
Now this is all just a way to derive what this little small d-arc or this little small arc length is

00:05:34.723 --> 00:05:38.333
but we don't want to find just a small arc length, we want to sum over all of them,

00:05:38.333 --> 00:05:41.975
so what we want to do is integrate the dt's,

00:05:41.975 --> 00:05:45.836
take the infinite sum of these infinitely small pieces right over here,

00:05:45.836 --> 00:05:53.667
these infinitely small arc lengths from t = 0 to t = 3.

00:05:53.671 --> 00:05:56.364
And so now we just do it.

00:05:56.364 --> 00:06:01.344
And so they tell us what x'(t) is and y'(t) is.

00:06:01.344 --> 00:06:02.692
Let me just rewrite the expression.

00:06:02.692 --> 00:06:13.926
This is going to be equal to the integral from 0 to 3 of the square root of x'(t) squared;

00:06:13.926 --> 00:06:20.867
the problem they give us what x'(t) is, its 4t + 1.

00:06:20.867 --> 00:06:32.933
So its 4t + 1 squared plus y'(t) squared...

00:06:32.933 --> 00:06:42.148
the derivative of y with respect to t is sine of t squared

00:06:42.148 --> 00:06:47.177
and we need to square that as well and then dt.

00:06:47.177 --> 00:06:51.271
And this is not a simple thing to find the antiderivative of,

00:06:51.271 --> 00:06:56.169
but lucky for us we are allowed to use our calculators in this part of the AP exam.

00:06:56.169 --> 00:07:01.067
And so all you have to do at this point, we've already done really the hard work,

00:07:01.067 --> 00:07:03.856
is use this definite integral function.

00:07:03.856 --> 00:07:14.164
It's in our catalog right over here and you can go straight to the 'f's and go a page down.

00:07:14.164 --> 00:07:21.123
We need to find the definite integral, we have to punch this into our calculator, of the square root of,

00:07:21.123 --> 00:07:26.405
(and I'll write it as x's just because the x button is much easier to get to than trying to put a variable t in there),

00:07:26.421 --> 00:07:44.215
so the square root of 4x plus 1 squared plus sine of x squared

00:07:44.215 --> 00:07:49.437
(instead of writing a t here, I'm just writing an x here, just to clarify what I'm doing)

00:07:49.437 --> 00:07:52.443
and then we want to square that,

00:07:52.443 --> 00:07:54.557
let's see, that closes that parentheses,

00:07:54.557 --> 00:07:57.533
and then I need to close the radical parentheses right over there.

00:07:57.533 --> 00:08:00.225
I want to say that my variable of integration is x

00:08:00.225 --> 00:08:04.298
I could have put t's here and set up my variable of integration as t, there's not any difference there

00:08:04.298 --> 00:08:09.877
and then I'm going between 0 and 3.

00:08:09.877 --> 00:08:17.892
And so, let's let the calculator do all the work here and we get...

00:08:17.892 --> 00:08:20.933
its taking a little time.

00:08:20.933 --> 00:08:24.067
We get 21.091.

00:08:24.067 --> 00:08:29.292
So this is equal to 21.091 and that's the entire arc length.

00:08:29.292 --> 99:59:59.999
That's the distance that this particle traveled.


2011 Calculus BC free response #1 (b & c)

WEBVTT
Kind: captions
Language: en

00:00:00.670 --> 00:00:04.550
Part b-- find the slope
of the tangent line

00:00:04.550 --> 00:00:09.180
to the path of the particle
at time t is equal to 3.

00:00:09.180 --> 00:00:12.350
So the slope of the
tangent line is just

00:00:12.350 --> 00:00:15.690
going to be equal to
the rate of change of y

00:00:15.690 --> 00:00:19.330
with respect to x at that point.

00:00:19.330 --> 00:00:26.349
And this is the same
thing as dy/dt over dx/dt.

00:00:26.349 --> 00:00:28.640
And dealing with differentials
is a little bit strange,

00:00:28.640 --> 00:00:30.810
especially when you want
to deal with rigorously,

00:00:30.810 --> 00:00:33.820
but you can view them as very
little, small changes in y,

00:00:33.820 --> 00:00:35.560
small changes in,
t small changes in

00:00:35.560 --> 00:00:37.050
x, small changes in t.

00:00:37.050 --> 00:00:39.290
When you view it this way,
you could say, hey, look.

00:00:39.290 --> 00:00:42.460
If I just multiply both
sides, both the numerator

00:00:42.460 --> 00:00:45.190
and the denominator,
by dt over dt-- which,

00:00:45.190 --> 00:00:47.950
if you do view them as
the same small change--

00:00:47.950 --> 00:00:49.620
then they would
cancel out, and you

00:00:49.620 --> 00:00:52.467
would get back to
the dy over dx.

00:00:52.467 --> 00:00:54.050
And the reason why
I wrote it this way

00:00:54.050 --> 00:00:57.980
is that they actually
give us these values.

00:00:57.980 --> 00:01:01.650
They give us dy/dt and
they give us dx/dt.

00:01:01.650 --> 00:01:11.040
So if you want to find the
slope at time equals 3,

00:01:11.040 --> 00:01:16.230
we just have to find dy/dt at
time equals 3 and dx/dt at time

00:01:16.230 --> 00:01:17.710
equals 3.

00:01:17.710 --> 00:01:21.320
So dy/dt at time
equals 3-- well,

00:01:21.320 --> 00:01:23.480
this is dy/dt right over here.

00:01:23.480 --> 00:01:26.650
It's just going to be sine
of 3 squared, or sine of 9.

00:01:29.370 --> 00:01:33.423
And dx/dt at time 3, that's
just going to be-- they

00:01:33.423 --> 00:01:35.560
tell us what dx/dt is
as a function of time.

00:01:35.560 --> 00:01:37.270
4 times 3 plus 1.

00:01:37.270 --> 00:01:40.429
Well, that is equal to 13.

00:01:40.429 --> 00:01:42.220
And then we can just
get our calculator out

00:01:42.220 --> 00:01:44.030
and evaluate this.

00:01:44.030 --> 00:01:46.020
We did a lot of this work
in the first problem.

00:01:46.020 --> 00:01:47.644
But let's just actually
take the value.

00:01:47.644 --> 00:02:01.035
So we have sine of 9 divided
by 13 gets as 0.0317.

00:02:01.035 --> 00:02:01.660
And we're done.

00:02:01.660 --> 00:02:03.480
That's the slope
of the tangent line

00:02:03.480 --> 00:02:07.020
to the path of the particle
at time t is equal to 3.

00:02:10.070 --> 00:02:11.020
I think we have time.

00:02:11.020 --> 00:02:13.930
We could crank out
part c as well.

00:02:13.930 --> 00:02:17.170
Part c-- find the position
of the particle at time t

00:02:17.170 --> 00:02:19.040
is equal to 3.

00:02:19.040 --> 00:02:25.990
So they give us x prime of t,
and they give us y prime of t.

00:02:25.990 --> 00:02:27.180
This is x prime of t.

00:02:27.180 --> 00:02:28.800
This is y prime of t.

00:02:28.800 --> 00:02:34.320
We need to figure out
x of x of 3 and y of 3.

00:02:34.320 --> 00:02:40.730
So if we can, let's
write x of t and y of t

00:02:40.730 --> 00:02:43.000
and then try to
evaluate them at 3.

00:02:43.000 --> 00:02:47.050
So let's see. x of
t is going to be

00:02:47.050 --> 00:02:50.420
equal to the antiderivative
of this right over here.

00:02:50.420 --> 00:02:56.529
So the antiderivative of 4t
is going to be 2t squared.

00:02:56.529 --> 00:02:57.570
Take the derivative here.

00:02:57.570 --> 00:02:58.790
You'll just get 4t.

00:02:58.790 --> 00:03:02.620
Antiderivative of
1 is t, plus t,

00:03:02.620 --> 00:03:04.620
and then you're going to
have a plus a constant.

00:03:04.620 --> 00:03:06.870
Or essentially, we just
took the indefinite integral

00:03:06.870 --> 00:03:09.450
of this side, of 4t plus 1.

00:03:09.450 --> 00:03:10.700
So you get your constant here.

00:03:10.700 --> 00:03:11.680
Because if you take
the derivative,

00:03:11.680 --> 00:03:13.304
this constant will
obviously disappear.

00:03:13.304 --> 00:03:14.810
You'll lose that information.

00:03:14.810 --> 00:03:18.430
Lucky for us, they also gave
us this initial condition.

00:03:18.430 --> 00:03:26.130
x of 0 is 0, when t is 0,
this term is going to be 0.

00:03:26.130 --> 00:03:28.244
This term is going to be 0.

00:03:28.244 --> 00:03:29.660
And they're saying
the whole thing

00:03:29.660 --> 00:03:30.743
is going to be equal to 0.

00:03:30.743 --> 00:03:32.930
So c is going to be 0, as well.

00:03:32.930 --> 00:03:35.920
Let me do that explicitly
just so we don't get confused.

00:03:35.920 --> 00:03:41.190
So x of 0 is going to be equal
to 0 plus 0 plus c, which

00:03:41.190 --> 00:03:43.510
they're telling
us is equal to 0.

00:03:43.510 --> 00:03:45.150
So c is equal to 0.

00:03:45.150 --> 00:03:47.870
So that tells us
that x of t is going

00:03:47.870 --> 00:03:51.660
to be equal to 2t
squared plus t.

00:03:51.660 --> 00:03:55.860
So if you want to
find x of 3, you just

00:03:55.860 --> 00:03:58.050
evaluate it right over here.

00:03:58.050 --> 00:04:00.470
So if you want to
find x of 3, it's

00:04:00.470 --> 00:04:03.510
going to be 2 times 9 plus 3.

00:04:03.510 --> 00:04:07.700
2 times 9 is 18, plus 3 is 21.

00:04:07.700 --> 00:04:09.750
So x of 3 is 21.

00:04:09.750 --> 00:04:12.320
Now let's try to do y of t.

00:04:12.320 --> 00:04:14.320
I'll do it in a different color.

00:04:14.320 --> 00:04:17.060
So let me scroll over to
the right a little bit.

00:04:17.060 --> 00:04:20.829
So let's say y of t is
equal to-- so if you

00:04:20.829 --> 00:04:23.745
try to take the
antiderivative of this,

00:04:23.745 --> 00:04:26.370
this is not simple to
take the antiderivative

00:04:26.370 --> 00:04:27.674
of this right over here.

00:04:27.674 --> 00:04:29.590
It's actually very hard
to do it analytically.

00:04:29.590 --> 00:04:31.750
Not even clear if you
can do it analytically.

00:04:31.750 --> 00:04:34.180
Lucky for us, this
part of the AP exam,

00:04:34.180 --> 00:04:36.070
we are allowed to
use calculators.

00:04:36.070 --> 00:04:37.839
So we could just say
this is equal to--

00:04:37.839 --> 00:04:39.880
and this is straight from
the fundamental theorem

00:04:39.880 --> 00:04:44.520
of calculus-- y of t is equal
to the integral from 0 to t.

00:04:44.520 --> 00:04:50.000
And I'll just write it
as sine of x squared dx.

00:04:50.000 --> 00:04:53.100
I didn't want to use a t here
and then use a t, as well.

00:04:53.100 --> 00:04:54.337
That would make it confusing.

00:04:54.337 --> 00:04:56.170
So you integrate with
respect to x, and then

00:04:56.170 --> 00:04:58.350
one of the upper bound
is going to be t.

00:04:58.350 --> 00:04:59.454
And this is y of t.

00:04:59.454 --> 00:05:01.870
And of course, you're going
to have to put a constant over

00:05:01.870 --> 00:05:04.339
here, because if you took
the derivative of this,

00:05:04.339 --> 00:05:06.380
you would get y of t, and
you'll lose information

00:05:06.380 --> 00:05:07.226
from this constant.

00:05:07.226 --> 00:05:09.100
Now, we can figure out
what that constant is,

00:05:09.100 --> 00:05:11.670
because they tell
us what y of 0 is.

00:05:11.670 --> 00:05:15.600
So y of 0 is going to be equal
to the integral from 0 to 0.

00:05:15.600 --> 00:05:17.630
So this part right over
here is going to be 0.

00:05:17.630 --> 00:05:20.656
So it's going to be equal to
c, which they tell us y of 0

00:05:20.656 --> 00:05:22.820
is also equal to negative 4.

00:05:22.820 --> 00:05:27.730
So we get y of t is equal
to the integral from 0

00:05:27.730 --> 00:05:33.130
to t of sine of x
squared dx minus 4.

00:05:33.130 --> 00:05:35.330
So that's y as a function of t.

00:05:35.330 --> 00:05:39.050
And we already figured
out what x of 3 is.

00:05:39.050 --> 00:05:41.470
Now we have to figure
out what y of 3 is.

00:05:41.470 --> 00:05:45.000
y of 3 is going to be
equal to the integral

00:05:45.000 --> 00:05:51.610
from 0 to 3 of sine of x
squared dx and then minus 4.

00:05:51.610 --> 00:05:55.040
And, once again, lucky for us,
we can use calculators here.

00:05:55.040 --> 00:05:58.660
So let's get the
calculator out, and we

00:05:58.660 --> 00:06:02.075
want to go to the
catalog of functions.

00:06:02.075 --> 00:06:04.430
So I press 2nd
Custom here, which

00:06:04.430 --> 00:06:06.145
gives us this little
catalog thing.

00:06:06.145 --> 00:06:07.770
And I want to do the
definite integral.

00:06:07.770 --> 00:06:09.930
And it's actually FN INT.

00:06:09.930 --> 00:06:10.960
So let me go to the F's.

00:06:14.680 --> 00:06:15.420
FN INT.

00:06:15.420 --> 00:06:18.400
So I have to go a
little bit further down.

00:06:18.400 --> 00:06:18.999
A little bit.

00:06:18.999 --> 00:06:19.540
There you go.

00:06:19.540 --> 00:06:21.690
That's my function
that I want to use.

00:06:21.690 --> 00:06:23.820
This is a definite
integral, and then I

00:06:23.820 --> 00:06:25.490
want to evaluate the
definite integral

00:06:25.490 --> 00:06:26.780
of this right over here.

00:06:26.780 --> 00:06:32.484
So the function is going
to be sine of x squared--

00:06:32.484 --> 00:06:34.650
that's what I want to
evaluate the definite integral

00:06:34.650 --> 00:06:39.635
of-- from 0 to 3.

00:06:42.310 --> 00:06:44.500
And my variable--
I need to see what

00:06:44.500 --> 00:06:46.690
the variable of
integration is first--

00:06:46.690 --> 00:06:48.350
so my variable of
integration is x,

00:06:48.350 --> 00:06:51.880
and I'm going to go from 0 to 3.

00:06:51.880 --> 00:07:00.210
And this gives me-- let the
calculator think a little bit--

00:07:00.210 --> 00:07:04.530
0.77356, and then to
that-- so that's just

00:07:04.530 --> 00:07:05.900
this first part right over here.

00:07:05.900 --> 00:07:07.760
And then I need to subtract 4.

00:07:07.760 --> 00:07:15.020
So minus 4 gives negative
3.226, I'll go with.

00:07:15.020 --> 00:07:18.384
So this is equal
to negative 3.226.

00:07:18.384 --> 00:07:19.550
Did I write that down right?

00:07:19.550 --> 00:07:20.480
I have a bad memory.

00:07:20.480 --> 00:07:23.580
Negative 3.226, and we're done.

00:07:23.580 --> 00:07:26.850
So y of 3 is equal
to negative 3.226.

00:07:26.850 --> 00:07:29.290
So the position of
the particle at time t

00:07:29.290 --> 00:07:32.740
equals 3, if you
wanted a coordinate,

00:07:32.740 --> 00:07:36.490
it would be 21, negative 3.226.