Comparing metabolism during ischemia and reperfusion in free flaps of different tissue composition

. Using microdialysis, the interstitial kinetics of glucose, lactate, pyruvate and glycerol were studied during ischemia and reperfusion in 39 human free flaps of different tissue compositions (skin, muscle and adipose tissue). The concentration of the substances were determined repeatedly during ischemia and reperfusion, and laser doppler flowmetry was used to document revascularization. Microdialysis catheters were placed in flap tissue and similar non-operated control tissue. Increased levels of lactate and glycerol and decreased glucose and pyruvate concentrations were observed in the flaps during ischemia. We were able to document different metabolic patterns because the various flaps consisted of different tissue. Variables involved in glycolysis (glucose, lactate and pyruvate) changed faster in muscle than in other flap tissues, whereas the glycerol increase was most evident in flaps that were composed predominantly of adipose tissue. During reperfusion all metabolites returned towards pre-ischemic levels within a few hours. However, pyruvate and glucose levels sometimes remained elevated over long periods (up to 24 h of reperfusion) in muscular flaps, possibly due to hypermetabolism, increased capillary flow or other unknown factors. It can be concluded that the dynamics of metabolism vary between flaps of different tissue compositions. This can be visualized during ischemia and reperfusion by using microdialysis.