The effects of systemic phenylephrine and epinephrine on pedicle artery and microvascular perfusion in a pig model of myoadipocutaneous rotational flaps.
BACKGROUND: Anesthesiologists and reconstructive surgeons have differing views regarding the control of rotational flap perfusion. Anesthesiologists view the entire body as having flow that is dependent on systemic perfusion pressure, whereas plastic surgeons conjure that systemic administration of vasoactive agents causes vasoconstriction of the pedicle artery and the microvasculature. The aim of this study was to investigate the effects of systemically administered phenylephrine and epinephrine on rotational myocutaneous flap perfusion. METHODS: After institutional animal care and use committee approval, seven vertical rectus abdominal myocutaneous (VRAM) flaps were created in six pigs. Under 1.0 minimum alveolar concentration isoflurane anesthesia, pedicle artery blood flow (transit time flow probe) and microvascular perfusion (laser Doppler flow probe) were recorded at baseline and after achieving steady hemodynamics with the systemic intravenous administration of phenylephrine (20, 40, and 80 microg/minute) and epinephrine (0.5, 1, and 2 microg/kg/minute). RESULTS: Under stable physiologic conditions, phenylephrine consistently decreased the pedicle artery blood flow and the microvascular perfusion of porcine VRAM rotational flaps, whereas epinephrine consistently increased both flows across the entire dose range studied. Furthermore, epinephrine-induced increases in cardiac output correlated well with the observed increases in pedicle artery blood flow and microvascular perfusion. CONCLUSIONS: With the systemic delivery of phenylephrine, rotational myocutaneous flaps react in a manner described by the surgeon. In contrast, the anesthesiologist's model of the hemodynamics is correct for low to moderate doses of epinephrine. Therefore, epinephrine may be the vasoactive agent of choice for treating perioperative hypotension without harming the rotational flap blood flow.
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