title: Monitoring of skeletal muscle oxygenation using near-infrared spectroscopy during abdominal aortic surgery.
abstract: OBJECTIVE
  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 (S(tO2)) was continuously monitored throughout the surgery.
  
  
  RESULTS
  The preoperative S(tO2) value was significantly lower in the AOD group (57.0 +/- 11.2%) than in the AAA group (68.7 +/- 7.0%). In both groups, S(tO2) significantly decreased after aortic cross-clamping; the maximal ischemic value of S(tO2) 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 S(tO2) returned to the preoperative level in the AAA group, whereas it increased above the preoperative value in the AOD group.
  
  
  CONCLUSIONS
  NIRS performed on the calf muscles is a useful method for assessing the changes in lower-leg perfusion during and after abdominal aortic surgery.