Massey MR & Gupta DK: The effects of systemic phenylephrine and epinephrine on pedicle artery and microvascular perfusion in a pig model of myoadipocutaneous rotational flaps (Plast Reconstr Surg 2007;120: 1289). The authors’ introduction succinctly summarizes the ongoing “conflict” between anesthesiologists and reconstructive surgeons. “Anesthesiologists view the entire body as having flow that is dependent on systemic perfusion pressure, whereas reconstructive surgeons conjure that systemic administration of vasoactive agents causes vasoconstriction of the pedicle artery and microvasculature.” To test the effects of vasopressors on pedicle flap perfusion the authors measured both pedicle artery and microvascular blood flow after various infused doses of phenylephrine (20, 40, and 80 mcg/min) or epinephrine (0.5, 1 and 2 mcg/kg/min) with drug testing starting at 1 hour after creation of a right vertical rectus abdominis myocutaneous rotational flap. At the completion of surgery this flap’s blood flow was supplied solely by a superior epigastric vascular pedicle. The pigs were euvolemic and normotensive at the start of drug challenge. There was a dose dependent fall in both pedicle artery and microvascular blood flow when phenylephrine was given. There was large variability between free flaps. In contrast there was a dose dependent increase in blood flow and microvascular perfusion when epinephrine was used (particularly the two lower doses). Microvascular flow measurements made on control (un-operated) skin showed an increase in blood flow with both phenylephrine and epinephrine; thus the free flaps in this study responded differently than normal skin. This study differs from some of the prior studies of vasopressors on free flaps in that the sympathetic innervation to the flap was not disrupted, nor was there a period of no flow with subsequent risk of ischemic injury. The applicability of a study in pigs to the human situation is always an unanswerable question. However, the microvascular perfusion measurements done can be applied in the operating room. The study did not address the issue of which is better for flap perfusion – hypotension secondary to the effects of the anesthetic, producing normotension with large volume crystalloid infusion, or correcting blood pressure with a small amount of vasopressor.
David S. Smith, M.D., Ph.D.
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