Dialock: a new vascular access device for extracorporeal renal replacement therapy. Preliminary clinical results

Vascular access, a vital tool for end-stage renal disease patients, remains a weak component of extracorporeal renal replacement therapy (RRT) and the first cause of morbidity. Permanent catheters proposed as an alternative to permanent AV fistulae are associated with a significant risk of infection. A subcutaneously implantable chamber connected to permanent catheter appears highly desirable to reduce such hazards.

Dialock, a metallic port-like valve device connected to permanent silicone twin catheters has been developed (Biolink Corp, Middleboro, MA, USA). After being implanted subcutaneously below the clavicle, Dialock provides a linear flow passage to two Silastic catheters placed in the right atrium via the right internal jugular vein. The valve is accessed percutaneously each dialysis session with needle cannulae that functionally convert the device into twin catheters. Interdialytic patency of the catheters is ensured by antithrombotic lock (heparin or low-molecular-weight heparin).

Dialock was implanted in 10 ESRD patients (64+/-12 years) under general anaesthesia, with almost immediate use for HD. RRT consisted of three HD sessions per week lasting 4 h; 699 HD sessions were performed. Average duration of use was 5.7 patient-months (1.3-9.6 months). Patient satisfaction was evident in all cases. Three episodes of bacteraemia occurring in the early phase of the study were cured by appropriate antibiotics. No device was removed because of infection. Skin condition at the puncture sites has remained satisfactory in all patients. Nurse training for cannulating was brief (2-3 x). Effective blood flow was 307+/-3.3 ml/min, with a venous pressure of 195+/-39 mmHg and a recirculation rate of 6.7+/-0.8%. Effective Kt/V dp delivered was 1.36+/-0.03 with a nPCR of 1.20+/-0.005 g/kg/day. Haematoma and a small amount of bleeding of the skin puncture sites observed in the initial period of the study were effectively prevented by reducing heparin lock volume.

The Dialock device offers a new and interesting vascular access alternative for haemodialysis bridging the 'gap' between permanent catheters and arteriovenous fistulae. Dialock's place in the vascular access strategy for haemodialysis patients deserves further long-term clinical studies.