Delayed microcirculatory hyperpermeability following perfusion washout.

Recent experimental data have demonstrated improved flap survival following perfusion washout with a synthetic, chemically defined, mammalian plasma. In an effort to define the physiology responsible for the efficacy of perfusion, the method of "labeling" hyperpermeable blood vessels with Monastral blue B in rat epigastric vascular island flaps was utilized. Results confirmed that capillary and venular hyperpermeability is an early and progressive pathophysiologic event in ischemic flap tissue and one which is reversible prior to a critical ischemic period. Perfusion washout with a physiologic, acellular plasma substitute delays the onset of vascular hyperpermeability. This may be a mechanism responsible for improving tissue survival following extended periods of warm ischemia (12 hours). It is implied that stagnant blood and products of hemolysis in the microcirculation may be detrimental to the functional and anatomic integrity of the endothelial wall.