Indwelling devices for vascular access in haemodialysis

Stanley Shaldon

7 Avenue des Papalins, Monaco

Sir,

Allow me to comment on the preliminary results of the use of a new device to facilitate vascular access reported by Canaud et al. [1]. The authors do not discuss the risk of pulmonary embolus associated with permanently indwelling vena-caval catheters. I reported such a fatal accident confirmed by autopsy in 1964 [2]. Presumably this risk is even greater if the catheters are placed in the right atrium as described in the earlier trial of this new device [3]. In the latter report there was a sudden fatal cardiac arrest on dialysis 3 weeks after implanting the device. As there was no autopsy, the possibility of a pulmonary embolus cannot be excluded in this case.

Whilst the problem of vascular access remains, one is not convinced that permanent indwelling catheters are likely to be the solution.

References

  1. Canaud B, Horn My, Morena M et al. Dialock: a new vascular access device for extracorporeal renal replacement therapy. Preliminary clinical results. Nephrol Dial Transplant 1999; 14: 692–698[Abstract]
  2. Shaldon S, Comty C, Sevitt L. 18 months experience with a nurse-operated chronic dialysis unit. Proc Eur Dial Transpl Assoc 1964; 1: 233
  3. Levin NW, Yang PM, Hatch DA et al. Initial results of a new access device for hemodialysis. Kidney Int 1998; 54: 1739–1745[ISI][Medline]

 

Reply

B. Canaud

Hôpital Lapeyronie, Montpellier, France

Sir,

Dr Shaldon raises an appropriate and interesting question concerning our paper that deserves further comments.

First, we all agree that permanent indwelling catheters are not the ideal vascular access for haemodialysis patients. However, the permanent catheter is a useful and vital tool in ESRD patients not having a permanent vascular access when dialysis is needed. Such a situation is observed in ESRD patients having exhausted their anatomical vascular access site, patients with contraindications for arteriovenous fistulae (cardiac failure, severe arteritis or diabetes) or patients with a native fistula which requires some time to mature.

Secondly, we agree upon the fact that permanent catheters are associated with an increased risk of thrombosis and pulmonary embolism. Indeed, any foreign material inserted into the blood stream activates clotting phenomena and inflammatory proteins, which predispose to venous and/or catheter thrombosis. It must be mentioned, however, that catheters are made of soft, atraumatic and haemocompatible silicone rubber material, which is far from the catheter first-generation as described by Dr Shaldon. In this study we did not observe any venous or atrial thromboses. Such low risk of thrombosis is in agreement with our previous results obtained in more than 1500 ESRD patients harboring dual rubber silicone catheters in which the risk of vein thrombosis was estimated to be inferior to 2%.

Thirdly, we also agree that atrial catheters may lead to an increased risk of thrombosis with the potentially serious hazard of pulmonary embolism. However, it is important to remember that as early as 1974, Broviac and Scribner proposed to position nutritional silastic catheters into the atrium—and the long-term results, more than 5 years, were excellent. Precise positioning of catheter tips into the right atrium was not required in our study. However, from clinical experience it is known that positioning the catheter tips at the level of the superior vena cava/atrium junction improved significantly their flow. It must also be pointed out that the distal part of both the arterial and venous line of the catheters is multiperforated (6–8 side holes in addition to the central hole). Such a design appears quite important, since it prevents the wall `jet lesion' that is observed with single central hole catheters.

By preventing mechanical lesions of the vessel wall, the multiple side holes of the distal part of catheter may therefore contribute to reduction of the risk of thrombus formation. In order to optimize catheter performance (both flow rate and recirculation), we and others recommend positioning catheter tips at the level of the junction of the superior vena cava and the right atrium. In a patient at high risk of thrombosis (inflammatory or prothrombotic state) we also recommend the use of anti-platelet agents or of low dose anti-vitamin K.

To conclude, permanent catheters with or without valve port device may be a vital necessity for ESRD patients. Catheter hazards must be known, accepted and minimized by appropriate indication and catheter care.





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