Cutaneous heat loss in children during anaesthesia

We have measured non-evaporative, cutaneous heat loss using heat flux transducers at eight skin sites in five children during anaesthesia and compared the data with basal metabolic heat production. The effect of disposable surgical covering and a radiant heater on heat flux was examined. The mean total heat flow rate before draping was 3-9 W higher than the basal metabolic rate after induction of anaesthesia with a simultaneous decrease in rectal temperature. Mean cutaneous heat loss was 62 (SD 9) W m-2 (9.5 (2.1) kJ kg-1 h-1) in children older than 1 yr and 84 W m-2 (17.2 kJ kg-1 h-1) in a 3-month-old infant. Disposable drapes diminished cutaneous heat loss by 29% and a radian heater by 77%. Heat conduction to the mattress was 21 (7) W m-2. These results showed that the decrease in core temperature after induction of anaesthesia was genuine cooling, that is heat loss exceeded heat production.