Evaluation of two warming systems after cardiopulmonary bypass

Abstract

We have compared the Thermomat electric undermattress (JMW Systems, Edinburgh, UK) and the Bair Hugger (Augustine Medical, Courtelary, Switzerland) forced-air warming blanket in 30 adult patients after cardiac surgery. All patients were warmed to an oesophageal temperature of 38 degrees C before termination of cardiopulmonary bypass (CPB); those with oesophageal temperatures < 35.5 degrees C at skin closure were allocated randomly to be rewarmed in the intensive care unit either on the Thermomat (n = 15) or under the Bair Hugger blanket (n = 15), at their highest settings. Oesophageal and lateral thigh skin temperatures were recorded every 15 min for 4 h. There was a significantly faster increase in core temperature (0.5 vs 0.75 degrees C h-1; P < 0.0002) and skin temperature (0.86 vs 1.3 degrees C h-1; P < 0.001) in the Bair Hugger group. However, there was no difference in the number of patients who reached a core temperature of 36 degrees C (15 Bair Hugger, 14 Thermomat) or 37 degrees C (11 Bair Hugger, seven Thermomat), or in the number of patients who reached a skin temperature of 37 degrees C in 4 h (four Bair Hugger, one Thermomat). Twelve patients in the Bair Hugger group reached a skin temperature of 36 degrees C compared with two in the Thermomat group (P < 0.001). The Bair Hugger warmed faster than the Thermomat both centrally and peripherally, and warmed more patients to a core temperature of 37 degrees C in 4 h, but did not reduce the time to tracheal extubation or alter important clinical aspects of postoperative course.

Forced-air warming and ultra-clean ventilation do not mix

“…Air-free alternatives, such as conductive fabric warming, have been developed that are comparably effective for the prevention of hypothermia. [8][9][10][11][12][13][14] These offer higher thermal efficiencies than forced-air warming and therefore release only a fraction of the excess heat. 6 Accordingly, we chose to compare the effects of forced-air and conductive fabric warming on clean airflow patterns over the surgical site in a partial-walled ultra-clean operating theatre during two simulated procedures: a hip replacement with upper-body warming, and a lumbar spinal procedure with lower-body warming.…”

Effect of forced‐air warming on the performance of operating theatre laminar flow ventilation*

“…Conductive heating devices employ an electrically heated pad in contact with the patient's body [7]. Both types of devices appear to be comparably effective for the prevention of accidental peri-operative hypothermia [8][9][10][11][12][13][14], although forced-air devices are less efficient in transferring the applied heat to the patient than conductive devices [15]. Therefore, we might expect forced-air devices to generate a greater excess heat load on the ventilation system.…”

Recommended Practices for the Prevention of Unplanned Perioperative Hypothermia

“…The method is effective in neonates, 87 pediatric patients, 85 and morbidly obese patients 88 . Forced‐air warming has also been found to be effective in rewarming patients after cardiopulmonary bypass 89–91 . Forced‐air warming does not increase the risk of wound contamination 83 , 92 …”