Seasonal Impact on Free Flap Surgery in Terms of Flap Loss and Wound Healing Disorders: A Retrospective Cohort Study of 158 Free Flaps.

(1) Background: Postoperative flap loss and wound healing disorders are severe complications after microsurgical free flap surgery. Despite multiple clinical observations, a possible influence of season and external temperature on outcome are largely missing. (2) Methods: Retrospectively, data were collected from 151 patients receiving microsurgical free flaps from March 2018 to August 2019. Patients were divided into two cohorts. The winter group includes all patients who underwent surgery from October 2018 to March 2019 and the summer group al those who underwent surgery from April 2018 to September 2018. Data included demographic information, pre-existing conditions, flap characteristics, and postoperative complications like flap losses and wound healing problems. External temperatures during the first 14 postoperative days were documented and the predictor of flap loss and wound healing disorders was detected. (3) Results: In the winter group (October-March; Ø 7.24 °C) 72 patients (46 female, 24 males; Ø 57.0 years) and in the summer group (April-September; Ø 18.79 °C) 81 patients (48 female, 33 males; Ø 56.0 years) received free flap surgery. There were no significant differences in demography (age: = 0.593; gender: = 0.419; BMI: = 0.141). We found a significant increase in flap loss during summer (χ(1) = 6.626; = 0.010; V = 0.209) strengthened by logistic regression analysis ( = 0.037; Exp(B) = 9.655). Additionally higher average temperatures 14 days postoperatively represents another main driver ( = 0.023, Exp(B) = 1.161) for postoperative flap loss. (4) Conclusions: The data confirm a significantly higher postoperative flap loss in the summer group. This information may potentially contribute to optimization of perioperative management and planning of elective and semi-elective surgeries.