Complications and treatment of mild hypothermia

Perioperative hypothermia triples the incidence of adverse myocardial outcomes. Mild hypothermia significantly increases blood loss and significantly augments allogeneic transfusion requirement. Only 1.9°C core hypothermia triples the incidence of surgical wound infection after colon resection and increases the duration of hospitalization by 20%. Redistribution hypothermia is the major cause of hypothermia during the first hour of neuraxial or general anesthesia. It can be minimized by actively warming peripheral tissues before induction of general or regional anesthesia. All effective noninvasive warming devices address the anterior skin surface because most heat is lost from this area. Passive insulation reduces cutaneous loss 30% (one layer) to 50% (three layers). However, active warming will be required to maintain normothermia in most patients. Forced-air and resistive heating are currently the most effective noninvasive options, although better systems are being developed. It is not possible to warm patients to any important extent by administration of heated intravenous fluids. However, each liter of fluid at ambient temperature decreases mean body temperature roughly 0.25°C in adults; each unit of refrigerated blood produces a similar reduction. Intravenous fluids should therefore be warmed when large volumes are required (ie., several liters per hour) or when forced air alone proves insufficient.