EFFECTS OF VASOACTIVE MEDICATIONS ON THE BLOOD-FLOW OF ISLAND MUSCULOCUTANEOUS FLAPS IN SWINE

Pedicled flaps and microsurgical free tissue transfers are increasingl y being used for reconstruction in the elderly and poorer risk patient . The use of systemically administered vasoactive agents to date has b een avoided because of the fear that systemic levels of these agents p erioperatively (particularly the vasopressors) might decrease blood fl ow 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 fl ap model in the pig that allows accurate, simultaneous monitoring of s ystemic and flap hemodynamic parameters such as flow and resistance an d (2) identify the effects of commonly used vasoactive substances (dop amine, dobutamine, and phenylephrine) at clinically used levels on sys temic and flap pressure/flow relationships. Vertically based rectus ab dominis musculocutaneous flaps were raised in 8 anesthetized, 50- to 5 5-kg pigs, and a flow probe was placed around the artery. Catheters wi thin the pulmonary artery and aorta were used to measure cardiac outpu t and aortic root pressures. Measures of arterial blood pressure, card iac output, and musculocutaneous flap flow were obtained at baseline a nd during the administration of varying doses of dopamine dobutamine a nd phenylephrine. Cardiac output increased significantly with low and high doses of dopamine and dobutamine, but decreased with increasing d oses 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 dopamin e and dobutamine. We conclude that (1) phenylephrine clearly affects f lap flow adversely in a large-animal musculocutaneous model and theref ore should be avoided, (2) dopamine does not affect total flap flow at either low or high doses despite increasing cardiac output, (3) dobut amine increases both flap flow and cardiac output, and (4) both dopami ne and dobutamine should still be used with caution because the flap f low is not equally increased relative to total cardiac output. Possibl e changes in systemic and flap metabolic demand induced by these vasop ressor drugs may therefore still be injurious to the flaps.