skip to main content

Tourniquet Deflation Physiology — FRCA Final MCQ

Instant feedback + full explanation. One question, done properly.

ModerateGeneral AnaesthesiaTourniquet Deflation PhysiologyFRCA Final

A 72-year-old man (ASA III) has a total knee replacement under spinal anaesthesia. A tourniquet is applied at 300 mmHg for 110 minutes. On deflation, what acute physiological changes should the anaesthetist anticipate?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — No significant changes if tourniquet time is <2 hours

Tourniquet deflation causes predictable physiological changes: (1) hypotension from reactive hyperaemia in the ischaemic limb (effective central hypovolaemia), (2) increased ETCO2 from washout of CO2 accumulated during ischaemia, (3) transient metabolic acidosis from lactic acid washout, (4) transient hyperkalaemia from potassium release, and (5) reduction in core temperature from cold blood returning from the ischaemic limb. These changes peak at 1-3 minutes post-deflation. The anaesthetist should pre-treat with fluid loading and be prepared with vasopressors.

Reference: AAGBI – 2020 – Tourniquet safety guidelines; RCOA – 2023 – Orthopaedic anaesthesia