Self-Warming Blanket Versus Forced-Air Warming in Primary Knee or Hip Replacement: A Randomized Controlled Non-Inferiority Study.

Objective: After primary total knee/hip replacement (TKR or THR respectively) a prosthetic joint infection (PJI) could develop. Hypothermia could raise the risk of infection. Heating by forced-air can disrupt laminar airfl ow in the operation room (OR), potentially raising the risk of infection. We aimed to study non-inferiority of an active self-heating blanket (SHB) compared to a forced-air blanket (FAB) in preventing hypothermia.

Methods: A randomized controlled non-inferiority trial (N = 86 patients) was performed comparing a SHB versus a FAB in elective primary TKR/THR patients. Primary outcome was lowest measured temperature during surgery. Secondary outcomes were patients' core temperature before, during, and after surgery, thermal comfort visual analogue score (VAS) and complications during hospitalization.

Results: Lowest measured temperature was 35.9°C (± 0.6) in SHB and 36.1°C (± 0.5) in FAB group (p = 0.05). No signifi cant correlation was found with duration of surgery or temperature of the OR. No signifi cant difference in core temperature was found before surgery (SHB = 36.8°C [± 0.4], FAB = 36.8°C [± 0.5], p = 0.49), after induction of anaesthesia (SHB = 36.6°C [± 0.5], FAB = 36.7°C [± 0.5], p = 0.22) nor as a mean during surgery (SHB = 35.8°C [± 1.6], FAB = 36.0°C [± 1.3], p = 0.68). SHB patients were "colder" at the recovery bay, 35.8°C (± 0.6) compared to FAB patients, 36.1°C (± 0.5) (p = 0.04). Mean VAS thermal comfort was 53.3 (± 15.7) in SHB and 52.9 (± 12.3) in FAB patients. No difference in complication rate was found.

Conclusions: In this study neither kind of the warming blanket prevented perioperative hypothermia. Although a difference of 0.2°C was found between both groups at the end of TKR/THR surgery, this is most probably not clinically relevant. Complication rate in both groups was the same.