Effects of vasoactive medications on the blood flow of island musculocutaneous flaps in swine.

Pedicled flaps and microsurgical free tissue transfers are increasingly being used for reconstruction in the elderly and poorer risk patient. The use of systemically administered vasoactive agents to date has been avoided because of the fear that systemic levels of these agents perioperatively (particularly the vasopressors) might decrease blood flow and compromise the viability of the flap. There are no large-animal, real-time hemodynamic studies that support or disprove this belief. The objectives of this study were to (1) develop a musculocutaneous flap model in the pig that allows accurate, simultaneous monitoring of systemic and flap hemodynamic parameters such as flow and resistance and (2) identify the effects of commonly used vasoactive substances (dopamine, dobutamine, and phenylephrine) at clinically used levels on systemic and flap pressure/flow relationships. Vertically based rectus abdominis musculocutaneous flaps were raised in 8 anesthetized, 50- to 55-kg pigs, and a flow probe was placed around the artery. Catheters within the pulmonary artery and aorta were used to measure cardiac output and aortic root pressures. Measures of arterial blood pressure, cardiac output, and musculocutaneous flap flow were obtained at baseline and during the administration of varying doses of dopamine dobutamine and phenylephrine. Cardiac output increased significantly with low and high doses of dopamine and dobutamine, but decreased with increasing doses of phenylephrine. Flap flow, on the other hand, is increased only with dobutamine but remains unchanged with dopamine despite increased cardiac output. Flap flow decreases with high doses of phenylephrine. Flap flow also decreases relative to cardiac output with both dopamine and dobutamine. We conclude that (1) phenylephrine clearly affects flap flow adversely in a large-animal musculocutaneous model and therefore should be avoided, (2) dopamine does not affect total flap flow at either low or high doses despite increasing cardiac output, (3) dobutamine increases both flap flow and cardiac output, and (4) both dopamine and dobutamine should still be used with caution because the flap flow is not equally increased relative to total cardiac output. Possible changes in systemic and flap metabolic demand induced by these vasopressor drugs may therefore still be injurious to the flaps.