Influence of control variables on mannequin temperature in a paediatric operating theatre

Background: Core temperature drops in all children having general anaesthesia. Convection heating may be useful, but its effectiveness in the paediatric setting is not established. Additionally, its utility in many paediatric situations is limited by blanket design. Methods: Using a mannequin model in a sham operation, we assessed the likely safety and effectiveness of a draping technique in association with a 'Bair Hugger' and a heat dissipation unit (HDU). In Part 1 of the study, the influence of ambient temperature was assessed. In Part 2, a simulated laparotomy was set up and a more detailed assessment of air temperatures around the mannequin was made. In addition, the effect of a change in the HDU design was assessed. Results: Part 1: the technique achieved 'near-plateau' temperature within 5-10 min. A difference of 8°C in ambient temperature (between 18 and 26°C) translated only to a 2-3°C difference under the drapes. Part 2: the technique produced sidestream cooler zones at the head and shoulders. Air temperature at these sites was 28-34°C, whereas at other points (irrespective of their distance from the heat source), it was 37-40°C. Warm air reached sufficient skin sites to anticipate adequate heat transfer in the clinical situation. Air temperature at 'skin' surface stayed below 40°C over the 90-min study period. Conclusions: A customized HDU used in association with a 'Bair Hugger' unit and a careful surgical draping technique provides stable, safe and consistent air temperatures around a mannequin. Net heat gain by a child's body should occur with this arrangement. Further evaluation in a clinical study is underway.