Micro-lightguide spectrophotometry for tissue perfusion in ischemic limbs.

ABSTRACT

OBJECTIVE: To validate micro-lightguide spectrophotometry (O2C) in patients with lower limb ischemia and to compare results with those obtained from toe blood pressure. METHODS: We 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 (SO(2)) 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. RESULTS: Median SO(2) 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 SO(2) values measured in the horizontal position and elevated position revealed a significant correlation (r(s) = 0.40; P < .01 and r(s) = 0.56; P < .01, respectively). A low SO(2) (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, SO(2) 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 SO(2) as well as toe pressure compared with the 10 patients with unobstructed flow to the foot. CONCLUSIONS: O2C 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.