Effect of forced-air warming system in prevention of postoperative hypothermia in elderly patients: A Prospective controlled trial

BACKGROUND: Postoperative hypothermia in elderly patients is a well-known serious complication as it impairs wound healing, induces coagulopathy, increases the risk of blood loss, enhances oxygen consumption, and precipitates cardiac arrhythmias. We conducted this randomized controlled trial to evaluate the effect of a forced-air warming system on rewarming elderly patients undergoing total knee or hip arthroplasty. METHODS: We recruited 243 elderly patients undergoing total knee or hip arthroplasty between May and December 2016. They were divided into three groups according to a computer-generated randomization table: group C (n = 78, rewarmed with only a regular blanket), group F1 (n = 82, rewarmed with a forced-air warming system set at 38°C), and group F2 (n = 83, rewarmed with a forced-air warming system set at 42°C). The nasopharyngeal temperature was recorded every 5 min for the first half hour, then every 10 min up to the end of the PACU (postanesthesia care unit) stay. The primary outcome was the rewarming time. The rewarming rate, increase in nasopharyngeal temperature (compared to the start of rewarming), hemodynamics, recovery time, and incidences of adverse effects were recorded. RESULTS: No significant differences were found among the three groups in terms of the baseline clinical characteristics, use of narcotic drugs, intraoperative temperature, and hemodynamics (P > .05). Compared with the elderly patients in groups C and F1, both the heart rate and mean arterial pressure of those in group F2 were significantly increased 20 min after arrival at the PACU (P < .05). Patients in group F2 had the shortest rewarming time (35.89 ± 6.45 min, P < .001), highest rewarming efficiency (0.028 ± 0.001°C/min, P < .001), and fastest increased nasopharyngeal temperature among the three groups. Moreover, the elderly patients in group F2 had lower incidences of arrhythmia and shivering (P < .05). CONCLUSIONS: The use of a forced-air warming system set at 42°C was shown to be the most effective way of rewarming elderly patients with postoperative hypothermia.