Effect of intra-arterially induced OC - receptor blockade upon resistance in collateral arteries in patients with occlusion of the superficial femoral artery

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Abstract
The effect of intra-arterially phentolamine inducing .alpha.-receptor blockade upon the resistance in collateral arteries bypassing an occlusion of the femoral artery was studied in 5 patients. The patients were placed on a tilt table and the measurements were performed with the patients in supine position and tilted 40.degree. (head-up). Arterial blood pressure was measured directly in the brachial, common femoral, and popliteal artery. Relative blood flow was calculated as the relative change in arteriovenous O2 saturation. Head-up tilt caused a decrease in blood flow of about 35% corresponding to an increase in total vascular resistance of 38%. Resistance in collateral arteries increased by 45%. In supine position, .alpha.-receptor blockade reduced collateral resistance by 17%. The tilt-induced constriction of the collateral arteries was blocked by 87%. The constriction of the collateral arteries bypassing an occlusion of the superficial femoral artery is mainly mediated via sympathetic adrenergic vasoconstrictor fibers.