SKIN PERFUSION-PRESSURE MEASUREMENT IS VALUABLE IN THE DIAGNOSIS OF CRITICAL LIMB ISCHEMIA

Purpose: Critical limb ischemia (CLI) is equated with a need for limb salvage. Arterial reconstruction and major amputation are the therapie s ultimately available to such patients. We studied whether measuremen ts of skin perfusion pressure (SPP) can be used to accurately identify those patients with CLI who require vascular reconstruction or major amputation and distinguish them from patients whose foot ulcer would h eal with local wound care or minor amputation. Methods: Fifty-three pa tients with a total of 61 limbs with a nonhealing foot ulcer (age rang e, 47 to 88 years; mean, 70.8 +/- 9.8 years; 33 men, 20 women) who wer e referred to the Vascular Laboratory at Morristown Memorial Hospital for evaluation of arterial insufficiency were studied in a prospective , double-blinded fashion. Patients were included in the study if infor med consent was obtained, and patients were excluded if there was unco ntrolled sepsis or if they required guillotine amputation. The size an d site of the foot ulcer was recorded. If gangrene was present, the lo cation and extent was also noted. The pulses were examined and recorde d, and the ankle-brachial index was determined for each limb. Measurem ents of SPP were made at the proximal margin of the ulcer in viable ti ssue (not in the bed of the ulcer). SPP measurements were made indepen dent of the vascular surgeon's evaluation of the limb and were not par t of his clinical decision regarding management of the foot ulcer. The SPP measurements were compared (Fischer's exact test) with the clinic al decision for therapy (group I, arterial reconstruction or major amp utation; or group II, wound debridement, minor amputation, or both). S PP was also compared with the outcome (ulcer healed or failed to heal) of therapy in group II. From contingency tables we calculated the sen sitivity, specificity, positive and negative predictive values (PPV, N PV), and the overall accuracy of SPP measurement diagnostic test for c ritical limb ischemia. Results: There was no difference in the size or location of foot ulcers between groups I and II, nor was there a diff erence in ulcer size or location between limbs that healed and did not heal in group II. The prevalence of diabetes was similar in all group s and subgroups. The ABI was not predictive of the need for reconstruc tion or major amputation nor the outcome of local therapy. SPP measure ments identified 31 of 32 limbs diagnosed as having CLI by clinical ev aluation (i.e., group I, those limbs that required vascular reconstruc tion or major amputation). Of those patients who were clinically asses sed as not having CLI (group II), SPP measurements diagnosed 12 of the 14 limbs that did not heal as having CLI (PPV, 75%) and 11 of 15 limb s that did heal as not having CLI (NPV, 85%). The sensitivity of SPP l ess than 30 mm Hg as a diagnostic test of CLI was 85%, and the specifi city was 73%. The overall diagnostic accuracy of SPP less than 30 mm H g as a diagnostic test of critical limb ischemia was 79.3% (p < 0.002, Fischer's exact test). Conclusions: We conclude that SPP measurement is an objective, noninvasive method that can be used to diagnose criti cal limb ischemia with approximately 80% accuracy.