CPB Rewarming — FRCA Final MCQ

Correct answer: E — 10°C

The correct answer is E: 10°C. During CPB rewarming, the gradient between oxygenator arterial outlet blood and venous inflow blood should not exceed 10°C. A larger gradient promotes liberation of dissolved gases as colder blood is rapidly warmed, increasing the risk of gaseous microemboli. The arterial outlet temperature should also remain below 37°C to avoid cerebral hyperthermia. Option A is a plausible distractor because, once arterial outlet temperature is at least 30°C, maintaining a gradient of 4°C or less is considered reasonable for controlled late rewarming and separation from bypass; however, it is not the absolute out-gassing safety limit asked here. Gradients of 6°C or 8°C are acceptable but are not the specified maximum, whereas 12°C exceeds it.

Reference: Engelman R, Baker RA, Likosky DS, et al. Clinical Practice Guidelines for Cardiopulmonary Bypass—Temperature Management During Cardiopulmonary Bypass, recommendations on peak warming temperature gradient, 2015. https://pubmed.ncbi.nlm.nih.gov/26279227/