Fistula size and hemodynamics: an experimental model in canine femoral arteriovenous fistulas.

PURPOSE: The objective was to evaluate the impact of anastomosis diameter on blood flow in an arteriovenous fistula (AVF), comparing two different anastomosis sizes with a modified side-to-side technique in canine femoral arteries. METHODS: Ten mongrel dogs were subjected to two AVFs each, both using a modified side-to-side technique. On one side, the anastomosis diameter was 1.5 times the arterial diameter and on the other side 3.0 times the arterial diameter. Mean proximal and caudal blood flow and mean venous flow were measured using an electronic flowmeter 15, 20 and 25 min after surgery. The Mann-Whitney, Friedman and Wilcoxon non-parametric tests were used for data analysis (alpha < or = 0.05). RESULTS: Femoral artery flow cranial to the fistula became 5.6 times greater in the 1.5 arterial diameter group, and 8.4 times greater in the 3.0 arterial diameter group, when compared to initial arterial flow. The mean flow in the cranial vein was greater in the 3.0 group (10.09 times greater vs. 6.46 times greater in the 1.5 group). Both in the proximal artery and in the vein there was a significantly greater flow in the group with the larger anastomosis diameter (Wilcoxon test). In the femoral artery caudal to the fistula, the flow in most of the animals was reversed: 3.5 times greater in the 1.5 group and 1.2 times greater in the 3.0 group, without statistical difference. CONCLUSIONS: These results suggest that 3.0 times the arterial diameter for the AVF size in dogs leads to greater venous flow than with 1.5 times the arterial diameter, without increasing the reversed flow.

Blood flow study of arteriovenous grafts with homologous and autologous veins in canine femoral vessels.

PURPOSE: The objective of this study was to assess the blood flow in arteriovenous (AV) communications comparing autologous and homologous veins, in the femoral vessels of dogs. METHODS: Ten mongrel dogs were used for the blood flow analysis, and two AV grafts (AVG) were placed in each of them. The grafts were made with an autologous vein in one side, and a omologous vein, kept in a 0.25% glutaraldehyde solution, in the other side. The volumetric flow was measured before and after AVG placement. Fifteen minutes after surgery, the volumetric flow was measured in the cranial artery, in the caudal artery, in the graft and in the vein, and the same procedure was repeated 15 days after surgery. Measurements were done using an eletromagnetic flowmeter calibrated previously. For data analysis, the Wilcoxon test was used (to compare the difference in the results between the times and the techniques used) alfa