Effect of active airway warming with a heated-humidified breathing circuit on core body temperature in patients under general anesthesia: a systematic review and meta-analysis with trial sequential analysis

Background: The application of a heated-humidified breathing circuit (HHBC) may re-duce respiratory heat loss during mechanical ventilation, but its effect in preventing intra-operative hypothermia is controversial. This study aimed to investigate the effectiveness of HHBC in maintaining the core temperature of patients receiving mechanical ventilation under general anesthesia.Methods: We searched MEDLINE, Embase, Cochrane library (CENTRAL), and Google Scholar to identify all randomized controlled trials (RCTs) up to February 2022 that com-pared the intraoperative core temperature in patients with heated humidifier (HH) and other circuit devices. The primary outcome was the intraoperative core temperature at the end of surgery. The weighted mean differences (WMDs) between the groups and their 95% CIs were calculated for each outcome. We performed a trial sequential analysis of the primary outcomes to assess whether our results were conclusive.Results: Eighteen RCTs with 993 patients were included in the analysis. A significantly higher core temperature was observed at the end of surgery in patients with HH than those with no device (WMD = 0.734, 95% CI [0.443, 1.025]) or heat and moisture ex-changer (WMD = 0.368, 95% CI [0.118, 0.618]), but with substantial heterogeneity.Conclusions: Although HHBC did not absolutely prevent hypothermia, this meta -analy-sis suggests that it can be used as an effective supplemental device to maintain the intraop-erative core temperature under general anesthesia. However, considering the substantial heterogeneity and limitations of this study, further well-designed studies are needed to clarify the effectiveness of HHBC.

Automated summary

This study investigated the effectiveness of heated-humidified breathing circuit (HHBC) in maintaining the core temperature of patients receiving mechanical ventilation under general anesthesia. The analysis of 18 randomized controlled trials revealed that patients with HHBC had significantly higher core temperature at the end of surgery compared to those without any device or with heat and moisture exchanger. This suggests that HHBC can be used as an effective supplemental device to maintain intraoperative core temperature.