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

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 five patients. The patients were placed on a tilt table and the measurements were performed with the patients in supine position and titled 40 degrees (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 arterio-venous oxygen 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%. However, the title-induced constriction of the collateral arteries was blocked by 87%. The results indicate that the constriction of the collateral arteries bypassing an occlusion of the superficial femoral artery is mainly mediated via sympathetic adrenergic vasoconstrictor fibres.