Regional hemodynamics of large and small femoral arteriovenous fistulas in dogs.

Alterations in regional hemodynamics were determined after construction of side-to-side femoral arteriovenous fistulas in dogs to quantitate the relationship between fistula size and reversal of distal arterial blood flow. When fistula size exceeded the transverse diameter of the femoral artery and vein (large fistula group), reversal in distal arterial blood flow was observed in all fistulas and measured 48 +/- 7 ml. per minute. If the fistula size were approximately equal to these critical transverse diameters (small fistula group), distal arterial flow was reduced but reversal did not occur. Distal arterial and venous pressures were 42 +/- 5 and 35 +/- 4 mn. Hg, respectively, for the large fistula group, and these pressures were 79 +/- 5 and 17 +/- 2 mn. Ht, respectively, for the small fistula group. These pressure changes for the two groups were significantly different and may provide a better understanding of the physiology of the reversal phenomenon.