The predictive value of laser Doppler fluxmetry and transcutaneous oximetry for clinical outcome in patients undergoing revascularisation for severe leg ischaemia

Abstract

To investigate the predictive value of laser Doppler fluxmetry and transcutaneous oximetry in 41 patients undergoing technically successful revascularisation for severe leg ischaemia. Toe and ankle systolic arterial pressures, transcutaneous oxygen tension (tcpO2), and stressed laser Doppler fluxmetry at the foot (time to peak laser Doppler flux following 2 min arterial occlusion, tp LDF, and the response of LDF to raising the leg 40 cm, the elevated:supine LDF ratio) were measured before revascularisation. Six months later these measurements were compared in those patients who were clinically improved, and those who still had symptoms of severe ischaemia or had lost their limb. Vascular Laboratory, St. George's Hospital, London SW17, U.K. Six months following revascularisation 30 (73%) of the 41 patients had partial or complete symptomatic relief. Six (15%) had undergone major amputation and five (12%) still had symptoms of severe ischaemia. Before intervention toe and ankle systolic pressures were similar in the 30 who were improved and the 11 who had lost, or were still at risk of losing, their leg. Pre-revascularisation tcpO2 was significantly lower (18.3 mm Hg vs 33.5 mm Hg; p < 0.05) and tp LDF significantly longer (140 s vs 92 s; P < 0.05) in the 11 patients who were not clinically improved at 6 months. Whilst pre-revascularisation toe and ankle pressures below 30 mm Hg and 50 mm Hg respectively identified only 55% of those patients who were not improved 6 months later, a tp LDF in excess of 100 s identified 82% (p < 0.05) and was noted in five of the six amputees. Microcirculatory assessments performed in patients with limb-threatening ischaemia are likely to be more deranged in those patients who suffer clinical failure or amputation despite an apparently successful revascularisation procedure.