Micro-lightguide spectrophotometry for tissue perfusion in ischemic limbs

ObjectiveTo validate micro-lightguide spectrophotometry (O2C) in patients with lower limb ischemia and to compare results with those obtained from toe blood pressure.MethodsWe prospectively examined 59 patients, 24 of whom complained of claudication, 31 had critical ischemia, and four were asymptomatic. Diabetes was present in 19 (32%) patients. Saturation (SO2) and flow measured with O2C were determined with the limb in the horizontal position followed by a 55-cm elevation. Toe pressures were determined in the horizontal position only. In addition, 13 patients were examined before and, on average, 3 days after revascularization.ResultsMedian SO2 was 62% (25%-75% percentile: 37%-75%) with the limb in the horizontal position and 16% (3%-41%) with the limb elevated. Comparing the individual toe pressures with SO2 values measured in the horizontal position and elevated position revealed a significant correlation (rs = 0.40; P < .01 and rs = 0.56; P < .01, respectively). A low SO2 (ie, <40% in the horizontal position and <20% in the elevated position) was highly predictive of a toe pressure of 40 mm Hg or less. In the horizontal position, the positive predictive value was 100%, whereas the negative predictive value was 47%. The similar figures in the elevated position were a positive predictive value of 97% and a negative predictive value of 68%. Postoperatively, SO2 increased significantly from 27% (P25%-75%: 11%-75%) to 79% (68%-87%) in the horizontal position (P = .008) and from 14% (P25%-75%: 2%-39%) to 55% (30%-73%) in the elevated position (P = .011), respectively. Looking at the individual 13 cases in which revascularization was performed, three patients had a partial reconstruction (ie, superficial femoral artery occlusion distal to a central reconstruction or reconstruction to a popliteal blind segment). These patients had significantly lower postoperative SO2 as well as toe pressure compared with the 10 patients with unobstructed flow to the foot.ConclusionsO2C was easy to use, fast, and painless. The most useful finding was the high predictive value of a low saturation and the rise in O2C values after successful revascularization.