SIADH true is all except?
Ans. is 'b' i.e., Urine Na+ is normal or slightly low Clinical criteria to diagnose SIADHDecreased plasma osmolarity (<280 mosm/kg)Hyponatremia (dilutional hyponatremia with Na+ <135 mmolAbsence of fluid volume depletion.In appropriate urinary osmolarity >150 mosm/Kg.Increased urinary sodium excretion >30 meq/L. While on normal salt and water intake.Water loading test in SIADHA water loading or ADH testing is sometimes performed in patients with hyponatremiaIn this test specific quantities of water is given to the patient and the amount of urine produced and the changes in urine osmolarity and blood osmolarity are monitored.With this test the patients with SIADH typically show decreased serum sodium and osmolality but not normal urine sodium and quantity of urine.They do not produce as much urine as expectedA normal person should excrete >90% of the water load within 4 hours whereas patients with SIADH are not able to excrete more than 20-30% of the water loadThe urine osmolality is high relative to serum osmolality.This suggests that patients do not excrete adequate water load.Management of SIADHGeneral principles used in the management of SIADH Fluid restriction It is the mainstay of the treatment of most patients with SIADH with a suggested goal intake of less than 800 ml/day.In addition to fluid restriction the therapy of SIADH associated hyponatremia often requires the administration of sodium chloride either as oral tablets or intravenous saline.When using intravenous saline, the osmolality of the administered fluid must be greater than the osmolality of urine (This is achieved by administering hypertonic saline).Among patients with urine osmolality more than twice the plasma osmolality, a loop diuretic may be used to reduce urinary concentration.Vasopressor receptor antagonist (Vaptans)Vasopressor receptor antagonists increases free water excretion without the loss of any sodium or potassium.Intravenous conivaptan (which is used in hospitalized patients) and oral tolvaptan are available and approved for use in patients with hyponatremia due to SIADH.The utility of vaptan therapy is limited byExcessive thirstProhibitive cost (at least in the united states) andThe potential for overtly rapid correction of hyponatremia which has led to the necessity for hospitalization for the initiation of therapy.Only one of the vasopressor antagonist i.e. conivaptan has been approved for short term in hospital I. V. treatment of SIADH and the hyponatremia of congestive heart failure.Others are currently in phase III trials.Choosing, the appropriate therapyThe choice of therapy in patients with hyponatremia due to SIADH varies with the severity of hyponatremia and the presence or absence of symptoms. a) Patients with severe hyponatremia who present with seizures or other severe neurological abnormalities or with symptomatic hyponatremiaIn these cases urgent intervention with hypertonic saline is requiredIn these patients the serum sodium has fallen below 120 meq/L in less than 48 hrs leading to potentially fatal cerebral edema.These patients require urgent interventionIt consists of 100 ml bolus of 3% saline - If neurological symptoms persist or worsen100 ml bolus of 3%saline can be repeatedHypertonic saline preserve cerebral perfusion and prevent complications from hyponatremia induced brain edema, swelling.The intravenous hypertonic saline increases serum sodium concentration by approximately 1.5 meq/L and 2.0 meq/L in women.Mild to moderate symptomsLess severe neurological symptoms (e.g. dizziness, gait disturbance, forget fullness, confusion, lethargy)These are seen in patients with a serum sodium concentration below 120 meq/L that develops over more than 48 hrs.Initial therapy in these patients depends in part upon the severity of symptoms.Confusion and lethargyThese patients require initial administration of hypertonic saline therapy. The serum sodium should be raised at the rate of 1meqLL/hour for three to four hours.For patients with mild symptoms (forget fullness, gait disturbances)These patients do not require administration of hypertonic saline.In these patients the initial therapy consists of fluid restriction and oral salt tablets.Asymptomatic hyponatremiaThese patients have serum sodium b/w 120-129 meqLL.These patients are often treated only with fluid restriction.However, some of these seemingly asymptomatic patients have subtle neurological manifestation that can interfere with the quality of life and that may be improved by raising the serum sodium by the following methods.VaptansSaltsLoop diuretics (in patients with urine osmolality more than twice that of the plasma)Goal of serum sodium * Serum sodium should be maintained at 130 meq/L or higher in patients with SIADH because of possible presence of subtle neurologic manifestations and falls when the serum sodium is b/w 120-129 meq/L.
Serum Na can be as low as 135
Urine sodium is normal or slightly low
Vaptans are new FDA approved drugs for its Rx
Water loading test can be used
Pituitary and Hypothalamus