Experimental model of haemodialysis in conscious sheep.

The aim of the study is to propose easy and standardized extracorporeal cir culation and haemodialysis techniques in conscious sheep. Ten sheep having a body weight between 50 and 70 kg were used in order to evaluate the effec tiveness of the model. The sheep were fitted with permanent large-diameters catheters implanted under anaesthesia in both the carotid artery and jugul ar vein for extracorporeal circulation. In addition, nine sheep were bilate rally nephrectomized during the implantation procedure. In each sheep, 4 ho urs haemodialysis sessions were performed. Heparin was administered as a bo lus injection (10 000 IU) in the venous catheter followed by continuous inf usion (5 000 IU/h) into the extracorporeal circuit. Non nephrectomized shee p underwent haemodialysis sessions twice a week as long as their catheters were functional. The sheep were discared when their catheters could no long er ensure 300 ml/min blood flow rates. The number of dialysis sessions real ized and the length of patency of the vascular access flows were noted. Blo od clotting was assessed with activated partial thromboplastin time (APTT) prolongation activity. Four haemodialysis sessions were performed in nephre ctomized sheep, 3, 5, 7 and 9 days after nephrectomy. Dialysis efficiency w as assessed with blood biochemical parameters correction. In non nephrectom ized sheep, the heparinization procedure increased APTT by about 6 times as compared to control plasma and prevented clot deposition in the extracorpo real circuit. The catheters provided clot-free blood access for 26 +/- 4.5 days and the sheep underwent 6.5 +/- 0.7 haemodialysis sessions. The absenc e of kidneys was efficiently supplied by haemodialysis sessions during the 9 days of the anephric period. The ovine haemodialysis model provides a use ful tool for the evaluation of new biomaterials and new haemodialysis strat egies. It also enables to artificially induce plasma modifications and to c ontribute to survival of sheep with experimental renal failure.