The Clinical Role of Intraoperative Core Temperature in Free Tissue Transfer.

Background: Lengthy microvascular procedures carry hypothermia risk, yet limited published data evaluate the overall impact of core temperature on patient and flap morbidity. Although hypothermia may contribute to complications, warming measures are challenged by conflicting reports of intraoperative hypothermia improving anastomotic patency.
Methods: A retrospective review included all free flaps performed by plastic surgeons at an academic medical center from December 2005 to December 2010. Intraoperative core temperatures were measured by esophageal probe, and median values recorded over 5-minute intervals yielded a case mean (Tavg), maximum (Tmax), and nadir (Tmin). Outcomes included flap failure, pedicle thrombosis, recipient site infection and complications associated with patient, and flap morbidity. Analysis used Student t test, Fisher exact test, Probit, and logistic regression.
Results: Of 156 consecutive free tissue transfers, the median Tavg, Tmax, and Tmin were 36.5°C, 37.1°C, and 35.8°C, respectively. The flap failure rate was 7.7% (12/156) and pedicle thrombosis occurred in 9 (6%) cases. Core temperatures did not associate with overall flap failure or pedicle thrombosis but recipient site infection occurred in 21 (13%) patients who had significantly lower mean core temperatures (Tavg=36.0°C, P<0.01). Lower Tavg and Tmax significantly predicted recipient site infection (P<0.01 and P<0.05, respectively). Cut-point analysis revealed significant increases in recipient site infection risk at Tavg less than 37.0°C (P=0.026) and Tmin less than or equal to 34.5°C (P=0.020).
Conclusions: Intraoperative hypothermia posed significant risk of flap infection with no benefit to anastomotic patency in free tissue transfer.