In vivo effects of prostacyclin on segmental vascular resistances, on myogenic reactivity, and on capillary fluid exchange in cat skeletal muscle

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Abstract
Objective To analyze the local circulatory effects of prostacyclin in skeletal muscle. Design A prospective experimental study. Setting A university laboratory. Subjects Twelve adult cats. Interventions The study was performed on autoperfused, sympathectomized gastrocnemius muscle. Measurements and Main Results Arterial blood flow, total and segmental vascular resistances (arterial vessels of >25 micro meter, arterioles of 25 micro meter. Hydrostatic capillary pressure increased by 1.9 +/- 0.3 mm Hg, causing fluid filtration. The relative fluid filtration was less than that value shown for some other vasodilator drugs (isoprenaline, calcium-channel blockers, thiopental) in this muscle preparation. Capillary filtration coefficient decreased by 25%. Myogenic reactivity was depressed but to a lesser extent than previously observed for other vasodilator mechanisms (muscle exercise, beta-adrenergic receptor stimulation, thiopental infusion, nifedipine infusion). Conclusions Prostacyclin is a vasodilator, both on the arterial and venous side, that restricts the increase in hydrostatic capillary pressure. The decrease in capillary filtration coefficient most likely reflects a decrease in capillary permeability, explaining the smaller relative filtration rate. The relatively well-preserved myogenic reactivity may imply a better preserved microvascular flow distribution and peripheral oxygen uptake. (Crit Care Med 1995;23:523-531)