Question

In hypovolemic shock there is -

• A. Afferent arteriolar constriction
• B. Efferent arteriolar constriction
• C. Increased blood flow to kidney
• D. Normal cardiac output

Answer 1

The Correct Option is A

Step 1: Begin with the haemodynamics of hypovolemia. Less circulating volume means less venous return, a smaller stroke volume and a fall in cardiac output. The body must defend blood pressure and perfusion of the brain and heart.
Step 2: The compensatory baroreceptor and sympathetic reflex raises heart rate and clamps down on systemic arterioles. The kidney is sacrificed: powerful sympathetic tone constricts the renal afferent arteriole, dropping renal blood flow so that blood is redirected to essential organs. Hence afferent arteriolar constriction is the right answer.
Step 3: Cross off the rest. Kidney blood flow is reduced, not increased. Cardiac output is depressed, so it is not normal. Selective efferent constriction is the angiotensin-mediated trick to preserve GFR in milder states, but the prevailing change in shock is afferent constriction with falling renal flow.
\[\boxed{\text{Afferent arteriolar constriction}}\]