The effects of hypotension and norepinephrine on microvascular flap perfusion.

Microvascular flap surgery is a common technique in reconstructive surgery. The wide indications and variable patients provide challenge also for anesthesiologist. Both hypotension and hypoperfusion can be harmful to the flap. Hypotensive patients are treated with fluid resuscitation and vasopressors (e.g., norepinephrine), if needed. As vasoconstrictors, vasopressors might impair microvascular flap perfusion. In this experimental pig model we studied the effect of sevoflurane-induced hypotension on the perfusion of microvascular and superiorly pedicled rectus abdominis myocutaneous flaps. In addition, we evaluated the effect of norepinephrine on flap perfusion when it was used for correction of hypotension. Microdialysis (MD) was used to detect metabolic changes, as it is a sensitive method to detect early changes of tissue metabolism and ischemia in different tissue components of soft tissue flaps. The main finding of this study was that moderate degree of normovolemic hypotension or the use of norepinephrine for the correction of this hypotension did not affect flap perfusion as assessed by MD. More studies are clearly needed to confirm the safety of norepinephrine in clinical use in microsurgery.