Metabolic response in microvascular flaps during partial pedicle obstruction and hypovolemic shock

To investigate tissue metabolism during suboptimal blood perfusion, we used in situ microdialysis in an experimental model of myocutaneous flaps. We assessed concentrations of glucose, lactate, and pyruvate in flaps subjected to partial pedicle obstruction and to hemorrhagic shock. When the arterial flow was restricted, the glucose concentration decreased in the flap muscle, and the lactate concentration increased in all flap components. The restriction ofvenous outflow resulted in lactate overproduction and a decrease of glucose in skin and muscle. The lactate-to-pyruvate ratio remained normal during arterial obstruction but increased during venous obstruction. During hypovolemic shock, the lactate production increased and the glucose concentration decreased or remained normal. The metabolic changes occurring during partial pedicle obstruction and hypovolemic shock are moderate and different from those seen in total pedicle obstruction. Microdialysis is a feasible method for assessing local tissue metabolism and can be used to monitor flap ischemia.