Cold

Though we manipulate a lot of parameters in surgery, one of the more unique and simultaneously mundane ones is temperature. In medical school, I wondered why temperature was a vital sign; sure, it's important to know if a patient has a fever, but how is it as important as the blood pressure or oxygen saturation? Why the focus on temperature?

At the beginning of anesthesia residency, I also found the fuss over temperature unnecessary. We learn the effects of general anesthesia on body heat homeostasis, the consequences on infection, bleeding, and shivering, and methods of rewarming. But for most short adult cases, temperature changes are inconsequential. In contrast, pediatric anesthesiologists obsess on temperature because children, infants, and neonates lose heat rapidly, and the smallest patients don't have the normal compensatory mechanisms to keep themselves warm.

In neurologic surgery, however, we want our patients to be cold. Though the benefit of mild hypothermia during brain surgery is not clear in randomized clinical trials, the theory makes sense. If the brain is cold, its metabolic demand decreases, and periods of decreased flow, retraction pressure, and surgical manipulation will have less of an effect. Indeed, in cardiac arrest, cooling the patient can lead to better long-term neurologic outcomes. So during some brain surgeries, we actively cool the patient down with a water blanket, and rewarm as the surgeons finish up. The timing is critical; to get a 200lb patient from 37 to 34 is no easy task, and returning him back to a relatively warm state for the end of surgery takes a little planning.

Image of Adolph Northern's Napoleon's Retreat from Moscow is in the public domain, from Wikipedia.