Intentional hypothermia is often used following the initiation of CPB. Core body temperature may be reduced to 20–32°C. In recent years, so-called tepid bypass has been used; this may be accomplished by allowing the patient’s temperature to “drift” down-ward to 30–35°C. Metabolic oxygen requirements are generally halved with each reduction of 10°C in body temperature. At the end of the surgical pro-cedure, rewarming via the heat exchanger restores normal body temperature.For complex repairs, profound hypothermia to temperatures of 15–18°C allows total circulatory arrest for durations of as long as 60 min. During that time, both the heart and the CPB machine are stopped.The adverse effects of hypothermia include platelet dysfunction; reversible coagulopathy; and depression of myocardial contractility.
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