How to get away from the cold: body temperature during surgery

the heroine and eventually died of hypothermia. A patient who enters the cold environment of an operating room is also at risk of becoming hypothermic. The human thermoregulatory system usually maintains the core body temperature near 37 o C. Temperature control is accomplished through a feedback mechanism involving the central nervous system. The hypothalamus acts as a thermoregulatory center to increase or decrease total body temperature. Core temperature is monitored by structures such as the tym-panic membrane, pulmonary artery, distal esophagus, and na-sopharynx, which can detect hypothermia as well as malignant hyperthermia. Although an increasing core temperature is not the first sign of acute malignant hyperthermia, it can help confirm the diagnosis. However, the most common perioperative thermal disturbance by far is inadvertent hypothermia, which increases the chances of myocardial ischemia [1]. Several studies have shown that hypothermia also slows the healing of surgical wounds and increases the incidence of surgical site infections [2]. Even moderate hypothermia (35 o C) can modify the platelet functions and enzymatic reactions that underlie physiological coagulation. Decreased platelet activity can lead to increased bleeding, which may necessitate a transfusion [3]. Hypothermia can also reduce the metabolic rate, leading to a prolonged effect of certain drugs used during anesthesia and some uncertain effects. This is particularly significant in elderly patients [4]. Shivering is a response to cold that is characterized by involuntary muscular activity, the purpose of which is to increase metabolic heat. However, many patients complain of discomfort caused by shivering in the recovery room [5]. Thermoregulation is impaired during general anesthesia. The suppression of thermoregulatory defense mechanisms during general anesthesia is dose-dependent and mostly results in perioperative hypothermia [6]. In this issue of Korean Journal of Anesthesiology (KJA), Lim et al. [7] report that a combined interscalene block and general anesthesia reduced the concentration of desflurane and prevented intraoperative hypothermia during arthroscopic shoulder surgery. The core temperature of patients who receive only an interscalene block should be monitored to evaluate the effect of the block alone. Although an in-terscalene block may affect sympathetic nerve activity, the body temperature of the patients decreased less with decreased doses of the volatile anesthetic agent. When inhalational anesthesia was maintained at a constant concentration, the vasoconstric-tion threshold during combined epidural-general anesthesia was lower and the core temperature was decreased further than for general anesthesia alone [8]. These results indicate that the shielding effect of the decreased temperature, …