Mammals need to maintain a nearly constant internal temperature. If the internal temperature deviates substantially from normal, metabolic functions generally deteriorate. The human thermoregulatory system usually maintains a core body temperature near 37°C. Perioperative hypothermia, however, is common because of the inhibition of thermoregulation induced by anesthesia and the patient's exposure to a cool environment. Hypothermia leads to numerous complications, including coagulopathy, morbid cardiac events, and a decreased resistance to surgical-wound infection. Normal Thermoregulation The processing of thermoregulatory information has three components: afferent thermal sensing, central regulation, and efferent responses. Together, they work to maintain the normal core body temperature. . . .

Mild perioperative hypothermia.

THE combination of anesthetic-induced impairment of thermoregulatory control and exposure to a cool operating room environment makes most surgical patients hypothermic. Several prospective, randomized trials have demonstrated various hypothermia-induced complications. There is no widely accepted definition for the term mild hypothermia. Furthermore, the term is not even used consistently in the literature. For the purpose of this review, mild hypothermia refers to core temperatures between 34 and 36°C.

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Complications and treatment of mild hypothermia

Hypothermia, defined as a core temperature less than 35 degrees C, is frequently not recognized, in part because of the inadequacy of standard thermometers. This entity has multiple causes and unique pathophysiologic consequences that complicate diagnosis and treatment. Understanding of the physiology of thermoregulation is important in light of recent advances in therapy using core rewarming. Pathophysiology, etiology and management of the hypothermia syndrome are reviewed.

Hypothermia: Pathophysiology, Clinical Settings, and Management

Intraoperative warming therapies: a comparison of three devices.

The hypothesis that forced-air warming preserves core temperature better than circulating-water mattresses was tested in: (a) 16 adults undergoing major maxillofacial surgery, including radical node resection and flap reconstruction; (b) 53 adults undergoing hip arthroplasty, having approximately 25% of their body surface area available for warming; (c) 20 infants undergoing minor maxillofacial surgery; and (d) 10 young children undergoing pelvic or femoral osteotomies. Patients having each type of surgery were randomly assigned to forced-air warming (approximately 40 degrees C) or conductive warming using a full-length circulating-water mattress at 40 degrees C. Forced-air warming was applied to the legs of the adults undergoing maxillofacial surgery and to one arm, the shoulders, and the neck in the adults undergoing hip arthroplasty; a U-shaped, tubular forced-air cover was positioned around the pediatric patients. Core temperatures increased in all patients given forced-air warming and decreased or remained constant in those without active warming. Furthermore, we needed to decrease the temperature of the warmer from high to medium (approximately 37 degrees C) in most patients assigned to forced-air warming to prevent hyperthermia. After 15 h of anesthesia, rectal temperatures in the adults undergoing maxillofacial surgery were 3.4 degrees C higher in the forced-air group (P < 0.01). After 4 h of anesthesia, esophageal temperatures had increased 0.8 +/- 0.5 degrees C in the patients warmed with forced-air and decreased 0.8 +/- 0.3 degrees C in those warmed by circulating-water mattresses (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Eugene L. Nagel

Papers

Thermal Burns Caused by Warming Blankets in the Operating Room

Anesthetic management of a patient with recessive epidermolysis bullosa dystrophica.

Effects of mast suit on central venous pressure in the sitting position

Failure of inflatable cuff resulting in foreign body in the trachea.

Immunoglobulins in Anesthesiologists