Monitoring of skeletal muscle oxygenation using near-infrared spectroscopy during abdominal aortic surgery

Purpose. To examine the utility of near-infrared spectroscopy (NIRS) in assessing lower-leg perfusion, NIRS was performed on the calf muscles of patients who underwent abdominal aortic surgery. Methods. Thirty patients undergoing elective infrarenal abdominal aortic surgery for abdominal aortic aneurysm (AAA group; n = 16) and aorto-occlusive disease (AOD group; n = 14) were studied. Before induction of anesthesia, NIRS probes were placed over both calf muscles, and muscle oxygen saturation (StO2) was continuously monitored throughout the surgery. Results. The preoperative StO2 value was significantly lower in the AOD group (57.0 ± 11.2%) than in the AAA group (68.7 ± 7.0%). In both groups, StO2 significantly decreased after aortic cross-clamping; the maximal ischemic value of StO2 in the AAA group (17.8 ± 7.2%) was significantly lower than that in the AOD group (46.7 ± 17.1%). The time taken to reach maximal ischemia was significantly longer in the AAA group (30 ± 12 min) than in the AOD group (19 ± 12 min). After release of the aortic clamp, the decreased StO2 returned to the preoperative level in the AAA group, whereas it increased above the preoperative value in the AOD group. Conclusion. NIRS performed on the calf muscles is a useful method for assessing the changes in lower-leg perfusion during and after abdominal aortic surgery.