Long-term blood access by catheters implanted into arteriovenous fistulas of sheep.

Reliable long-term blood access in sheep was provided by implanting one or two catheters into the high velocity blood flow in the vein draining an arteriovenous fistula created in the neck. Thrombosis of the catheterized vein occurred in only one of 31 cases in which a catheter with rounded intravascular tip was used, as compared with seven in 10 cases using a sharp-tipped catheter. The mean duration of placement for all rounded-tip catheters was 228.6 days. Extrusion from the vessel occurred with 3 of 8 short catheters (2 cm intravascular length), but only after a period of more than seven months of implantation. Using a program of trice-weekly disinfection of the skin exit site, exterior portion of the catheter, and catheter lumen resulted in failure of only two catheters due to infection. Rounded-tip catheters with 5 cm intravascular length had 75% life table functional rate at 15 months. Implantation of two catheters permitted extracorporeal circulation at flows of up to 300 ml/min using a blood pump to withdraw blood from one catheter while simultaneously returning it through the second.