Post-resuscitation targeted temperature management (TTM) is initiated in a comatose survivor of out-of-hospital VF arrest. The target temperature of 33°C is maintained for 24 hours. The main concern with deep hypothermia (below 30°C) that makes 33°C preferable to aggressive cooling is:

• A Paradoxical cerebral vasoconstriction worsening ischaemia
• B J waves (Osborn waves) in the ECG indicating hypothermic arrhythmogenicity
• C Increased metabolic demand from shivering at 33°C
• D Coagulopathy, ventricular fibrillation, and immune suppression at temperatures below 30°C ✓

Explanation

Moderate hypothermia at 32–36°C confers neuroprotective benefit while avoiding the major risks of deep hypothermia below 30°C, which include coagulopathy (impaired coagulation factor function and platelet dysfunction), ventricular fibrillation (a major arrhythmic complication at <28–30°C), and immune suppression increasing infection risk. J/Osborn waves on ECG do appear at 32–35°C but are diagnostic markers, not the primary contraindication to deeper cooling. Shivering is a problem at TTM temperatures and requires active suppression, but this is a complication of the technique, not the reason for avoiding temperatures below 30°C.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.