The purpose of this study is to determine the lowest concentration of subcutaneous phenylephrine (neosynephrine) required for effective vasoconstriction in skin graft donor sites. Surgery for burn injury is associated with blood loss. Tourniquet use and tumescence with epinephrine have decreased blood loss. However, absorption of epinephrine has been reported with systemic effects. Phenylephrine, an α1-adrenergic receptor agonist, has vasoconstrictive properties similar to epinephrine's without other α-adrenergic or β-adrenergic activity. The aim of this study is to determine the lowest effective concentration of phenylephrine that will provide vasoconstriction in split-thickness graft donor sites. By using intensive care unit equivalency tables, the authors estimated a concentration of phenylephrine on the basis of current epinephrine tumescence. This concentration was titrated up or down according to an algorithm established a priori, determining the minimum concentration that achieved vasoconstriction in three consecutive patients. The primary outcome was local vasoconstriction. Secondary outcomes measured were pre-, intra-, and postoperative mean arterial pressure, systolic pressure and heart rate, graft take, and donor site healing. The subjects were six otherwise healthy adult patients (five men and one woman) with a mean age of 36 years. The average TBSA was 737.5 cm². Vasoconstriction was achieved at 5 μg/ml. No significant alterations in hemodynamic measures were observed. The optimal concentration of phenylephrine for prevention of bleeding in donor sites appears to be 5 μg/ml. Participants will be able to identify the effects of phenylephrine and epinephrine tumescence. They will also identify the concentration at which phenylephrine will be effective in donor sites.