The safety and effectiveness of a modified convection heating system for children during anesthesia

Convection heating shows most promise in maintaining children's core temperatures under anesthesia. We have previously shown that a modified convection heating technique worked in a mannequin model and sought to establish its safety and effectiveness in a clinical study.

Children were recruited who were having elective surgery under general anesthesia lasting >90 min. The children were anesthetized and maintained in a room temperature of 21 degrees C. Warming was performed by a 'Bair Hugger' attached to a heat dissipation box, producing turbulent air from multiple outlet holes on its face. A plastic sheet covered the child, was attached to the top of the box, tucked into the sides of the bed and left open at the head end. Temperatures at various sites (air, skin, and core) were continuously monitored using thermistors connected to a datalogger and laptop. Analysis was performed using Excel.

The study comprised 40 children ranging in age from 2 days to 12.5 years and weigh 2.5-73 kg. Operations were 'peripheral' (e.g. urethroplasty) lasting 90 min to major laparotomy lasting 590 min. Body surface area uncovered was 5-25%. Skin temperatures rose to a maximum of c. 40 degrees C. Core temperatures rose after a 12-min lag by 0.01-0.04 degrees C x min(-1). In children who became hyperthermic, cooling was readily achieved by turning the heating off and leaving the fan running.

The technique is safe and effective for children throughout the pediatric range. The practice of increasing room temperature above 21 degrees C for elective cases should be abandoned. Continuous monitoring of core temperature is necessary to prevent hyperthermia.