Impact of Intraoperative Hypothermia on Microsurgical Free Flap Reconstructions

Background:  Patients requiring microsurgical defect reconstruction are highly susceptible to intraoperative hypothermia, given oftentimes long operative times and exposure of large skin surface areas. While the impact of hypothermia has been extensively studied across various surgical fields, its role in the setting of microsurgical free flap reconstruction remains elusive. This study evaluates the effects of hypothermia on outcomes of free flap reconstructions.

Methods:  Within 7 years, 602 patients underwent 668 microvascular free flap reconstructions. The cases were divided into two groups regarding the minimal core body temperature during free flap surgery: hypothermia (HT; < 36.0°C) versus normothermia (NT; ≥36.0°C). The data were retrospectively screened for patients' demographics, perioperative details, flap survival, surgical complications, and outcomes.

Results:  Our data revealed no significant difference with regard to the rate of major and minor surgical complications, or the rate of revision surgery between both groups ( > 0.05). However, patients in the HT group showed significantly higher rates of total flap loss (6.6% [HT] vs. 3.0% [NT],  < 0.05) and arterial thrombosis (4.6% [HT] vs. 1.9% [NT],  < 0.05). This translated into a significantly longer hospitalization of patients with reduced core body temperature (HT: mean 16.8 days vs. NT: mean 15.1 days;  < 0.05).

Conclusion:  Hypothermia increases the risk for arterial thrombosis and total flap loss. While free flap transfer is feasible also in hypothermic patients, surgeons' awareness of core body temperature should increase. Taken together, we suggest that the mean intraoperative minimum temperature should range between 36 and 36.5°C during free flap surgery as a pragmatic guideline.