Hemodynamics of Collateral Vasodilatation following Femoral Artery Occlusion in Anesthetized Dogs

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Abstract
Dilatation of collateral blood vessels was studied following occlusion of the femoral artery in anesthetized dogs. This was achieved by measuring pressure and flow in the anterior tibial artery distal to the occlusion and pressure in the femoral artery proximal to the occlusion. Dilatation of the collateral vessels to the anterior tibial artery was estimated by the increase in the conductance of the collaterals from the minimum value measured 8 to 10 seconds following onset of the occlusion. Conductance rose 277 ± 67 (SEM)% during the first 70 seconds following occlusion and an additional 178 ± 66% during the ensuing hour. When the femoral artery was reopened after a 2-minute period of occlusion, the collaterals reconstricted to their preocclusion size in 12 to 14 minutes. Elimination of circulatory reflexes by total spinal anesthesia did not alter the course of collateral vasodilatation. However, when systemic arterial pressure was lowered to approximately 45 mm Hg for 8 minutes prior to occlusion, the collaterals dilated almost completely even before the occlusion was instituted, indicating that tissue ischemia is in some way related to collateral vasodilatation.