A New Method to Control Ultrafiltration in Conventional Continuous Renal Replacement Therapy

Conventional continuous arteriovenous hemofiltration/hemodialysis (CAVH/D) and slow continuous ultrafiltration (SCUF) are types of continuous renal replacement therapy (CRRT) in which the ultrafiltrate (UF) volume is controlled imprecisely with a UF clamp, which is labor intensive, demanding frequent adjustment to preclude excessive fluid removal. We devised a simple method for precise control of the UF volume. Seven CRRTs in the form of CAVH, CAVHD, and SCUF were performed in four patients with massive edema. A standard circuit was created in each case using blood tubing sets and an HF 400 hemofilter obtained from MinnTech. Standard intravenous infusion tubing connected to an infusion pump (IMED, Gemini PC-2 volumetric pump/controller) with its proximal end inserted into the dialysate port at the venous end of the hemofilter, and the distal end draining into a plastic bag, was used to control the UF rate. Dialysis was added to the circuit using another pump connected to the dialysate port at the arterial end of the hemofilter. Treatment time ranged from 27 to 78 hours. Target fluid removal was achieved in all treatments, and the net UF rate required only once daily adjustment for total fluid intake. Mean time to reporting a problem by the intensive care nurse was 30 hours (range, 25-30 hours), and mean time to filter clotting was 38 hours (range, 27-40 hours). This set-up is less labor intensive, more cost effective, and is applicable in areas lacking automated machines. Future development of tubing for UF designed as above may further reduce cost.