The list of negative patient outcomes associated with unintended perioperative hypothermia is surprisingly long: wound infections, myocardial ischemia and cardiac disturbance, coagulopathy, prolonged and altered drug effects, increased mortality, shivering, pain and thermal discomfort, and delayed emergence from anesthesia. And it can all happen surprisingly fast. Unintended hypothermia can develop in the hour immediately following the induction of anesthesia. Even mild hypothermia can be associated with significant morbidity and mortality. Much has been written about how to prevent this frequent complication of surgery, but here's a quick refresher on the top 5 consequences of hypothermia that afflict millions of U.S. surgical patients every year.
- Increased wound infection. Hypothermia may increase patients' susceptibility to perioperative wound infections by causing vasoconstriction and impaired immunity. Hypothermia impairs the immune function and decreases cutaneous blood flow that reduces tissue oxygen delivery. This in turn increases the chance of a wound infection and also impairs the wound-healing process. Vasoconstriction occurs when the core body temperature decreases, which is a protective mechanism to divert blood to the center of the body and help maintain the normal body temperature. The reduction of nutrient and oxygen supply to wounds will increase the frequency of surgical wound infection. A threefold increase in the frequency of surgical site infections is reported in colorectal surgery patients who experience perioperative hypothermia.
- Cardiac dysfunction. Ventricular tachycardia in particular is associated with mild hypothermia. Angina, decreased cardiac output, and dysrhythmias can also be related to unintentional hypothermia. As little as 2°C core hypothermia can significantly increase the incidence of a myocardial ischemia in high-risk patients undergoing peripheral vascular surgery.
- Increased blood loss. Mild hypothermia reduces platelet function and decreases activation of the coagulation cascade. Therefore, hypothermia can increase blood loss and require transfusions during surgery. The literature shows that an approximately 2°C drop in core body temperature can increase blood loss by 500mL. Shivering post-operatively can cause an increase in oxygen demand, bleeding times and blood viscosity, and contribute to a risk for metabolic acidosis, along with hyperventilation and hypoxia.