A patient undergoes intravenous regional anaesthesia (Bier block) for closed reduction of a forearm fracture using prilocaine. The surgeon asks to deflate the cuff five minutes after injection to check reduction quality. Why must the anaesthetist refuse?

• A The block will regress completely within seconds of early deflation
• B Early deflation causes reflex pulmonary hypertension
• C Deflation within twenty minutes triggers rebound compartment syndrome
• D Systemic bolus release of local anaesthetic may cause CNS and cardiac toxicity before tissue redistribution ✓

Explanation

The safety of the Bier block depends on slow washout of drug from the isolated limb. Deflating the cuff within about 20 minutes releases a large venous bolus into the systemic circulation before redistribution into muscle and fat, risking perioral tingling, tinnitus, seizures and arrhythmia. Prilocaine is preferred because it has the widest therapeutic index of the commonly used agents. Early cuff cycling with brief reinflation is the accepted compromise if release is unavoidable.

Reference: Hadzic's Textbook of Regional Anesthesia and Acute Pain Management, 2nd ed.

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Written and medically reviewed by the StethoPrep medical team.