Transfusion criteria in free flap surgery

Objective: The ideal hematocrit for patients undergoing free flap reconstruction is unknown. It is standard practice to keep hematocrit levels above 30 percent, although there is evidence that blood transfusions are associated with both infectious and noninfectious complications. We propose that lowering the trigger for postoperative transfusions from 30 percent to 25 percent will not increase flap-related complications and may reduce unnecessary blood transfusions. Study Design: Observational cohort study. Setting: Tertiary care center. Subjects and Methods: Patients undergoing free tissue transfer from January 2007 through February 2008 received blood transfusions for hematocrit < 30 percent, whereas patients having surgery from March 2008 through April 2009 received blood transfusions for hematocrit < 25 percent. Outcomes include flap-related complications, length of stay, number of units transfused, and lowest postoperative hematocrit. Results: In the group transfused for hematocrit < 30 percent, 123 patients underwent 129 free flaps. In the group transfused for hematocrit < 25 percent, 122 patients underwent 135 flaps. The mean lowest postoperative hematocrit levels were significantly lower in the group transfused for hematocrit < 25 percent compared with the group transfused for hematocrit < 30 percent (26.6% vs 28.4%, respectively, P < 0.0001). The group with hematocrit < 25 percent also received fewer units of blood transfused (1.47 vs 2.11, P = 0.028). Complication rates between the two groups were not significantly different aside from higher rates of fistula and respiratory failure in the group transfused for hematocrit < 30 percent. Flap loss was 2.3 percent compared with 6.7 percent (P = 0.138). Conclusion: For patients undergoing free flap surgery, a postoperative transfusion trigger of hematocrit < 25 percent decreases blood transfusion rates without increasing rates of flap-related complications.