True about shock -a) In early stage cardiac output and BP are maintainedb) There is decreased sympathetic activityc) Renin secretion may be increased d) Aldosterone secretion is decreased
Stages of shock 

Shock tends to evolve through three general phages : -

A. Non progressive (Initial or compensated reversible) shock
In the early stage of shock, there is activation of compensatory mechanisms that attempt to maintain adequate perfusion of the heart and brain, and to maintain adequate cardiac output and blood pressure.
These compensatory mechanisms include : -
	1. Due to decrease perfusion pressure, baroreceptors are stimulated that leads to increased sympathetic discharge & catecholamines release with reduced vagal activity. All these cause : -
	a) Peripheral vasoconstriction Cool clammy extrimities (In hyperdynamic stage of septic shock and in neurogenic shock the extrimities are warm due to vasodilatation).
	b) Tachycardia
	2. Decreased renal perfusion and sympathetic stimulation cause increased renin release from the kidney and activation of renin angiotensin system. So that : -
Angiotensin II causes vasoconstriction and release of aldosterone.
Aldosterone causes fluid and salt conservation by kidney.
In this stage patient can be managed by correcting the underlying cause, e.g., fluid therapy in hypovolemic. Shock and control of infection in septic shock.

B. Progressive (Decompensated reversible) shock
Due to continued tissue hypoxia, aerobic respiration replaced by anaerobic glycolysis that leads to formation of lactic acid → Lactic acidosis & pH.
Acidosis (↓ pH) causes blunting of venoconstrictor effect of catecholamine → Venodilatation → Pooling of blood in peripheral veins. As there is arteriolar constriction ( ↑ peripheral resistance) and venodilatation (↓ venous return) → Cardiac output is decreased.
Peripheral pooling of blood and decreased cardiac output cause anoxic injury to endothelial cells that may cause DIC.
Decreased perfusion to vital organs like brain causes mental confusion & drowsiness and decreased perfusion to kidney causes decline in urinary output.
In this stage patient can be managed but more aggresive management is required i.e., along with correction of underlying cause; intropic agent, vasopressor, oxygen and resuscitation may be required.

C. Irreversible shock
Unless there is intervention in previous stages, the process enters in an irreversable stage in which there is multiple organ damage.
In this stage survival is not possible even after intervention.
a
bc
ac
b