Anesthesia duration and hypothermia affect graft survival in vascularized free flap surgery

Objective: The success rate of free flap revascularization is affected multifactorically. The aims of this study were to determine the anesthetic factors, with emphasis on hypothermia, in free flap failure and the relationship between hypothermia and free flap survival. Patients and Methods: We reviewed the anesthesia and medical records of patients undergoing free flap surgery from January 1995 to December 1999. The surgeries were all done by one surgeon in a medical center. During this period, 336 patients received free flap surgery. The data from 311 patients were collected and analyzed. The outcome of the surgery was evaluated and graded as successful, partially failed, or failed by the surgeon. Typically, an ischemic area larger than a quarter of the flap was rated as failed; between one fifth and a quarter of the area was rated as partially failed; and less than a fifth was rated as successful. Results: A total of 240 patients (77.2%) had successful flaps, while the other 71 patients (22.8%; 3.5% failed plus 19.3% partially failed) had failed ones. There were no statistical differences in gender, age, or hemoglobin level. Of note is that the total failure rate (partially failed plus failed cases) was significantly higher if the intra-operative body temperature was below 34 °C (57.14% vs 22.83%, respectively) or if the anesthesia duration was longer than 8 hours (P<0.05). Conclusions: Anesthesia durations longer than 8 h and intraoperative hypothermia below 34 °C might contribute to the failure of free flap surgery.