What makes a good flap go bad? A critical analysis of the literature of intraoperative factors related to free flap failure

Objectives/Hypothesis: The purpose of this article is to discuss the various factors related to poor outcome in free flap reconstructions of the head and neck (H&N). Free tissue transfer has become the standard reconstruction technique for complex H&N defects. With the evolution of free flap use in H&N surgery, numerous factors have been proposed that adversely affect flap outcome, many with the support of only anecdotal experience. We seek to critically review the literature to assess what evidence exists for the relation of various intraoperative factors to free flap complications. Study Design: Literature review. Methods: A review of the contemporary literature (1995 to present) on free flap reconstruction of the H&N was undertaken. A PubMed search using the terms head and neck, reconstruction, free flap, microvascular, failure, complications, fluids, intraoperative, hypertension, hypotension, nitrous oxide, temperature, and morbidity in various combinations was completed. Appropriate articles were selected and analyzed. Results: Studies report various factors thought to influence flap outcomes, often with divergent conclusions. Nonetheless, the body of evidence implicates several intraoperative factors to contribute to free flap complications including: >7 L intraoperative fluid administration, significant medical comorbidity, and prolonged operative time. There is no evidence supporting hypotension, pressors, colloids, and nitrous use in free flap failure. Conclusions: Although various dogmas related to the intraoperative care of free flap patients exist, including avoidance of hypotension and pressor use, there is no available clinical evidence to support these practices. Although free flap failure is uncommon, a better understanding of its causes is necessary to avoid this disastrous complication.