Risk of bias analysis.

Objective
Prewarming has been recommended to reduce intraoperative hypothermia. However, the evidence is unclear. This review examined if prewarming can prevent intraoperative hypothermia in patients undergoing thoracoscopic and laparoscopic surgeries.
Methods
PubMed, CENTRAL, Web of Science, and Embase databases were searched for randomized controlled trials (RCTs) up to 15th January 2024. The primary outcome of interest was the difference in intraoperative core temperature. The secondary outcomes were intraoperative hypothermia (<36°) and postoperative shivering.
Results
Seven RCTs were eligible. Meta-analysis showed that intraoperative core temperature was significantly higher at the start or within 30mins of the start of the surgery (MD: 0.32 95% CI: 0.15, 0.50 I2 = 94% p = 0.0003), 60 mins after the start of the surgery (MD: 0.37 95% CI: 0.24, 0.50 I2 = 81% p<0.00001), 120 mins after the start of the surgery (MD: 0.34 95% CI: 0.12, 0.56 I2 = 88% p = 0.003), and at the end of the surgery (MD: 0.35 95% CI: 0.25, 0.45 I2 = 61% p<0.00001). The incidence of shivering was also significantly lower in the prewarming group (OR: 0.18 95% CI: 0.08, 0.43 I2 = 0%). Prewarming was also associated with a significant reduction in the risk of hypothermia (OR: 0.20 95% CI: 0.10, 0.41 I2 = 0% p<0.0001). The certainty of the evidence assessed by GRADE was “moderate” for intraoperative core temperatures at all time points and “low” for minimal intraoperative core temperature, shivering, and hypothermia.
Conclusion
Moderate to low-quality evidence shows that prewarming combined with intraoperative warming, as compared to intraoperative warming alone, can improve intraoperative temperature control and reduce the risk of hypothermia and shivering in patients undergoing thoracoscopic and laparoscopic procedures.