Background: Although forced-air warming is the most commonly used method for perioperative patient warming, it is fundamentally problematic because it disturbs the carefully designed airflow in the operating room. Because unintended hypothermia has significant consequences, there is a need for more effective warming strategies. The effectiveness of warming technologies that apply heat through the skin is based on surface-area contact with the heat source and the duration of pre-warming. Therefore, we sought to test the therapeutic effectiveness of combined above- and below-warming therapies. Our hospital prohibits forced-air warming before the patient is draped, so a secondary goal was to determine the effect of preoperative warming using a system that does not interfere with airflow in the operating room.
Methods: We prospectively randomized 35 patients undergoing total knee arthroplasty into two groups: 1) forced-air warming/water mattress, using both WarmTouch® upper-body forced-air warming (Medtronic/Covidien Inc., Dublin, Ireland) and a Norm-O-Temp® underbody water mattress (CSZ/Gentherm Inc., Cincinnati, OH, USA), and 2) conductive fabric warming, using a HotDog® electric upper-body blanket (Augustine Temperature Management LLC, Eden Prairie, MN, USA) and a HotDog® underbody mattress.
Results: Throughout the surgical procedure, group 2 patients had significantly higher temperatures; this group experienced superior pre-warming during preoperative preparations and thus the redistribution temperature drop following the induction of anesthesia was reduced. Both groups achieved 100% normothermia by the end of surgery.
Conclusion: Based solely on the temperatures at the end of surgery, these data indicate that forced-air warming in conjunction with a water mattress warming system is as effective as a conductive fabric electric warming system alone.