Oxygenation and blood volume changes in flaps according to near-infrared spectrophotometry

Objective: To test the ability of near infrared spectrophotometry (NIRS) to predict vascular compromise in flaps postoperatively. Design: Pilot study. Subjects: Eleven denervated latissimus durst flaps were assessed in 8 pigs. Interventions: Flaps were isolated on their vascular pedicle. We used NIRS to demonstrate tissue oxygen saturation and quantities of deoxygenated hemoglobin and oxygenated hemoglobin when flaps underwent venous or arterial occlusions. Oxygen saturation (percentage of oxygenated hemoglobin) was calculated as the difference between the 2 light intensities (860-750 nm) with the use of 2 time periods: preoperative (80%) oxygen saturation and during arterial occlusion (0%) oxygen saturation with NIRS. Blood volume changes within the flap were also measured. Results: Arterial occlusion resulted in significant decreases in oxygen saturation and in blood volume with immediate recovery. Venous occlusion resulted in an initial rapid increase in blood volume with no appreciable early deoxygenation. Conclusions: Near-infrared spectrophotometry appears promising as a noninvasive, low-cost, portable bedside monitor that can demonstrate in real time changes in blood volume and oxygen saturation within a flap at a variety of tissue depths.