Intravenous infusion of iloprost in arterial occlusive disease: dose-dependent effects on skin microcirculation

Summary Transcutaneous oxygen pressure (tcPo₂), laser Doppler flux and capillary microscopy have been used to examine the forefoot skin in 5 healthy men and 8 patients with severe peripheral arterial occlusive disease in order to evaluate the dose dependent effects of iloprost on skin microcirculation. Iloprost was infused IV starting at 0.0625 ng·kg^–1·min^–1 and doubling the dose every 15 min up to 2 ng·kg^–1·min^–1.While tcPo₂ at an electrode core temperature of 44°C decreased in both patients and controls, there was a significant dose dependent increase in tcPo₂ (37°C) in the controls from 0.25 ng·kg^–1·min^–1. In the patients the reaction was variable: it was decreased in two and increased in 6, with a maximum either at 0.25–0.5 ng·kg^–1·min^–1 (n=3) or at the highest dose (1.0 or 2.0 ng·kg^–1·min^–1; n=3). Mean laser Doppler flux in both groups was increased, although the reaction was not consistent in the patients. Density of forefoot skin capillaries was reduced in 3 patients, and in the others the flow velocity was very low. During infusion of iloprost, both an increase in capillary density and blood cell velocity were observed. The effects were of variable intensity and occurred at varying doses, some appeared early and diminished as the dose was increased, and others were found only at 2 ng·kg^–1·min^–1.Adverse effects were numerous, extending from harmless skin flushing to mental changes and a quickly reversible attack of angina pectoris. It may be possible to divide patients into those with early effects on the microcirculation, at doses of 0.25–0.5 ng·kg^–1·min^–1, and those in whom the microcirculatory response is preceded and counteracted by the adverse effects.