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Comparison of forced-air patient warming systems for perioperative use
G G Giesbrecht1, M B Ducharme, J P McGuire
1Department of Anesthesia, University of Manitoba, Winnipeg, Canada.
Background:
Perianesthetic hypothermia is common and produces several complications, including postoperative shivering, decreased drug metabolism and clearance, and impaired wound healing. Forced-air warming transfers more than 50 W to the body and is an efficient method for either preventing or reversing decreases in core temperature.
Methods:
The authors compared the efficacy of four complete forced-air warming systems: (1) Bair Hugger 250/PACU Patient Warming System with 300 Warming Cover (Augustine Medical, Eden Prairie, MN); (2) Thermacare TC1000 Power Unit with TC1050 Comfort Quilt (Gaymar Industries, Orchard Park, NY); (3) WarmAir 130 Hypothermia System with 140 Warming Tube (Cincinnati Sub-Zero Products, Cincinnati, OH); and (4) WarmTouch 5000 Patient Warming System and 503-0810 CareQuilt (with the connecting hose compressed [short] and extended [long]) (Mallinckrodt Medical, St. Louis, MO). Six minimally clothed male volunteers were studied supine in a 24.5 degrees C environment. Cutaneous heat flux and skin temperature was measured at 14 area-weighted sites using thermal flux transducers. After 20-min control periods, volunteers were warmed for 40 min in each condition. A cotton blanket was placed over each cover. Power units were placed at the foot end of the bed, started cold, and set at maximum temperature and flow settings. All units reached maximum efficiency within 20 min.
Results:
Total heat transfer with the Bair Hugger system (95 +/- 7 W) was greater (P < 0.05) than with WarmTouch (short hose 81 +/- 6 W and long hose 68 +/- 8 W), Thermacare (61 +/- 5 W), and WarmAir (38 +/- 6 W) systems. Each cover also was tested on a common power unit (Bair Hugger 200). Total heat transfer was greater (P < 0.05) with the Warming Cover (Bair Hugger) (88 +/- 8 W), followed by the Comfort Quilt (Thermacare) (56 +/- 6 W), CareQuilt (WarmTouch) (50 +/- 7 W), and the Warming Tube (WarmAir) (43 +/- 6 W).
Conclusions:
The advantages of the Bair Hugger system and Warming Cover are evident in areas that are important for heat transfer from the periphery to the body core (chest, axilla, abdomen, and upper legs).