MCQ – 83594

Correct Answer � A Explanation

In hypovolemic shock, there is a severe ↓ in circulating blood volume (e.g., hemorrhage, dehydration, burns).

– ↓ preload → ↓ cardiac output → ↓ renal perfusion.
– Compensatory mechanisms aim to preserve perfusion to vital organs & maintain blood pressure:
– Sympathetic nervous system activation → systemic & renal vasoconstriction.
– Renin-Angiotensin-Aldosterone System (RAAS) activation:
– Angiotensin II → preferential efferent arteriolar constriction to maintain glomerular filtration.
– In severe hypovolemia, both afferent & efferent arterioles constrict, with afferent constriction predominating, leading to ↓ renal blood flow & GFR.
– Afferent arteriolar constriction contributes to oliguria & AKI in prolonged hypovolemic shock.

Incorrect Options:
B. Efferent arteriolar constriction – Predominates, but afferent constriction is more dominant due to sympathetic stimuli.
C. Increased blood flow – Renal blood flow ↓ to preserve flow to the brain and heart.
D. Normal cardiac output –Cardiac output is ↓ due to low preload from volume loss. Hypovolemic shock is marked by ↓ central venous pressure and ↓ cardiac output.