Hemodynamic effects of sympathectomy in ischemic canine hindlimbs

One week after unilateral distal superficial femoral artery ligation, 15 anesthetized dogs were studied before and after bilateral lumbar sympathectomy. Total hindlimb capillary (THC) flow and arteriovenous anastomotic (AVA) flow were determined by microsphere arteriovenous (A-V) shunt measurement combined with electromagnetic femoral artery blood flow measurement. Muscle capillary blood flow (MBF) was measured by xenon133 clearance. Baseline femoral blood flow in ischemic (I) hindlimbs was only 53% of contralateral control (C) hindlimbs (I = 56, C = 105 ml/min, P less than 0.01). Ischemia was manifest in I limbs by reduced O2 consumption (I = 1.68, C = 2.53 ml of O2/min, P less than 0.01). After sympathectomy, total blood flow increased significantly in I limbs, but no improvement in O2 consumption occurred. This was due to increased A-V shunting, with increased AVA flow (from 3 to 20 ml/min. P less than 0.01) but unchanged THC flow. Neither resting nor reactive hyperemic MBF improved after sympathectomy. Control limbs showed similarly increased AVA flow, but decreased O2 consumption, suggesting a detrimental effect of sympathectomy. The major hemodynamic consequence of sympathectomy in ischemic canine hindlimbs was increased nonnutritive A-V shunting, with no improvement in total capillary flow.