Epinephrine, norepinephrine, dobutamine, and dopexamine effects on free flap skin blood flow

The optimal sympathomimetic drug to support blood pressure without adverse vasoconstriction of free flap circulation remains unknown. This study examined the effects of four agents (epinephrine, norepinephrine, dobutamine, and dopexamine) on free flaps following resection of head and neck cancer.

Twenty-four patients (25 data sets) were recruited into the study. Each patient received an infusion of the four drugs in a random order, with an intervening washout period between drugs, at four infusion rates. Continuous free flap skin blood flow monitoring was performed using laser Doppler velocimetry, with a second sensor on normal skin acting as a control. Global cardiovascular variables were monitored using the LiDCO Rapid Pulse Contour Analysis System (LiDCO Ltd., Cambridge, United Kingdom).

Dose-dependent, increased free flap skin blood flow was observed with norepinephrine and dobutamine. Both dopexamine and epinephrine infusions decreased blood flow. Flap skin blood conductance decreased (vasoconstriction) with norepinephrine, but markedly less than in control tissue, so overall the flap skin blood flow increased with increasing arterial blood pressure. Dobutamine increased flap skin conductance, without significantly increasing blood pressure, and modestly increased flap blood flow.

Both dobutamine and norepinephrine had beneficial effects on flap skin blood flow. The maximal improvement in flow occurred with norepinephrine, making it the optimal pressor to use in patients with hypotension after free flap surgery.