Renin trigger — FRCA Primary MCQ

Correct answer: D — Renin rises with reduced afferent arteriolar pressure

Reduced renal perfusion pressure is a key trigger for renin release. Right ventricular afterload rises with pulmonary vascular resistance is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Perfusion of non-ventilated alveoli creates shunt is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Citrate binds ionised calcium is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. The loop of Henle creates the medullary osmotic gradient is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA physiology, the correct answer is usually the variable that best explains the observed change in the anaesthetised patient.

Reference: West's Respiratory Physiology; Ganong Review of Medical Physiology; Primary FRCA textbooks