Sympathetic reflex control of resistance in collateral arteries in the lower extremities in patients with diabetes mellitus.

The vascular response in the lower extremities to 40 degrees head-up tilt was studied in 5 patients with occlusion of the superficial femoral artery and maturity onset diabetes mellitus with symptoms suggesting autonomic neuropathy. The pressure measurements were performed via catheters placed in the brachial artery, femoral artery and vein and popliteal artery and vein. Relative blood flow was calculated as the relative change in arterio-venous oxygen saturation. Absolute blood flow in the common femoral artery was measured by an indicator dilution technique. Resistance of the collateral arteries increased by 40% during head-up tilt compared with horizontal position. Total leg resistance increased by 24%. Vascular resistance did not change below the knee. Intra-arterial alpha-blockade abolished the increase of vascular constriction in the leg during head-up tilt indicating that alpha-adrenergic tone was present in limbs studied.