Tissue pH monitoring in microsurgery: a preliminary evaluation of continuous tissue pH monitoring as an indicator of perfusion disturbances in microvascular free flaps

In an experiment using a continuous tissue pH monitoring system, selective occlusion of the vessels supplying lower abdominal island flaps in Sprague-Dawley rats resulted in predictable tissue pH changes. Arterial occlusion resulted in a rapid fall in pH. In all three experimental groups, the steepest rate of pH drop occurred during the first 30 minutes postocclusion. In a series of 9 patients who underwent microvascular free flap surgery the continuous pH monitor was employed postoperatively. Tissue pH was (and remained) normal in well-perfused free flaps. Tissue pH fell almost immediately with anastomotic failures. These findings demonstrate that pH measurement offers the microvascular surgeon a new, simple, and reliable approach to perfusion assessment in free flaps. Perhaps improved survival rates will result from earlier anastomotic exploration in compromised free flaps that exhibit falling pH values.