Which physiological change is desirable during cardiopulmonary bypass in terms of temperature?

Hypothermia is a desirable physiological change during cardiopulmonary bypass (CPB) for several reasons. Lowering the body temperature during surgery reduces the metabolic rate of tissues and organs, which leads to a decreased demand for oxygen. This is particularly important in situations where blood flow may be temporarily interrupted or reduced, as it helps to protect vital organs from ischemic damage.

By inducing hypothermia, the body can tolerate periods of reduced blood supply more effectively. Furthermore, hypothermia can help to reduce the risk of neurological injuries and improve patient outcomes in cardiac surgeries involving CPB. It also facilitates better management of coagulation and can help mitigate the inflammatory response associated with CPB.

While normothermia, or maintenance of a normal body temperature, can be desirable during certain surgical procedures, hypothermia is specifically targeted in the context of CPB for its protective effects and advantages in reducing metabolic demands. Hyperthermia, on the other hand, would be detrimental during CPB as it increases oxygen consumption and metabolic rates, which could lead to complications. Thus, hypothermia is indeed the physiological state preferred during cardiopulmonary bypass.