Improved survival of acute skin flaps with amino acids as free radical scavengers.

Oxygen-derived free radicals have been shown to be important mediators in ischemia-reperfusion injury to skin flaps. Agents that reduce the level of these free radicals have been used to improve flap survival in model systems. An in vitro study of the interactions between amino acids and hydroxyl radicals by electron spin resonance spectroscopy suggests an intrinsic radical scavenging activity of certain amino acids. The ability of these amino acids to improve acute axial-random skin flap survival was examined in a rat model. Cysteine, methionine, proline, hydroxyproline, histidine, and phenylalanine, given intravenously, significantly improved flap survival over saline controls; alanine gave an intermediate result, while aspartic acid showed no improvement. The in vitro data were generally a good predictor of free radical scavenging ability as manifested by improved flap survival in vivo. Biochemical mechanisms and clinical applications are described.