Deliberate mild hypothermia is occasionally discussed for cerebral protection during aneurysm surgery. The physiological basis for its protective effect is that for every 1 degree Celsius fall in body temperature, cerebral metabolic rate for oxygen decreases by approximately:

• A 2 percent
• B 6 to 7 percent ✓
• C 15 percent
• D 25 percent

Explanation

Cerebral metabolic rate falls by roughly 6 to 7 percent for every 1 degree Celsius reduction in temperature, which proportionally reduces cerebral blood flow requirements and prolongs tolerance of temporary arterial occlusion. This Q10 relationship underlies the rationale for cooling in circulatory arrest and deep hypothermia techniques. A 2 percent figure understates the effect, while 15 and 25 percent would correspond to drops of two to four degrees Celsius respectively.

Reference: Miller's Anesthesia, 9th ed.

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Written and medically reviewed by the StethoPrep medical team.