Thermal management during anaesthesia and thermoregulation standards for the prevention of inadvertent perioperative hypothermia

Incidence of inadvertent perioperative hypothermia is still high, and thus thermoregulatory standards are warranted. This review summarizes current evidence of thermal management during anaesthesia, referring to recognized clinical queries (temperature measurement, definition of hypothermia, risk factors, warming methods, implementation strategies). Body temperature is a vital sign, and 37°C is the mean core temperature of a healthy human. Systematic review shows that for non-invasive temperature monitoring the oral route is the most reliable; infrared ear temperature measurement is inaccurate. Intraoperatively, acceptable semi-invasive temperature monitoring sites are the nasopharynx, oesophagus and urinary bladder. Clinically relevant hypothermia starts at 36°C with regard to major adverse outcomes (increased infectious complications, morbid cardiac events, coagulation disorders, prolonged length of hospital stay, and increased costs). Skin surface warming for 20min immediately before anaesthesia (pre-warming) minimizes initial redistribution hypothermia. Intraoperatively, active warming should be applied when anaesthesia time is >60min. Effective methods of active warming are forced-air warming or conductive warming, provided that enough skin surface is available. Infusion fluid warming, increasing the operating room temperature, and warming of irrigation fluids are adjunctive therapies. The patient's body temperature should be above 36°C before induction of anaesthesia, and should be measured continuously throughout surgery. Active warming should be applied intraoperatively. Postoperative patient temperature and outcomes should be evaluated.

Key words: normal body temperature, temperature monitoring, perioperative hypothermia, pre-warming, active patient warming, outcome evaluation