During haemorrhagic shock, which of the following cardiovascular responses occurs LAST as compensatory mechanisms are sequentially overwhelmed?

• A Transcapillary refill (movement of interstitial fluid into the capillary)
• B Activation of baroreceptor reflex causing tachycardia and vasoconstriction
• C Release of ADH and activation of RAAS
• D Lactic acidosis-induced myocardial dysfunction and decompensated hypotension ✓

Explanation

The compensatory sequence in haemorrhagic shock proceeds from immediate to delayed responses. First (within seconds), baroreceptor reflex produces tachycardia and arteriolar/venous constriction via sympathetic activation. Next (minutes), neurohumoral activation — catecholamine surges, ADH release, and RAAS activation — augments vasoconstriction and reduces renal sodium and water excretion. Then (30 minutes to hours), transcapillary refill draws interstitial fluid into the vascular compartment. Progressive tissue hypoperfusion causes anaerobic metabolism, lactic acidosis, and eventually myocardial dysfunction and irreversible decompensation — the latest and most ominous event in the sequence.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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