Department of Nephrology, Virga Jesseziekenhuis, Hasselt, Belgium
Sir,
In a recent letter to the editor, Bayés et al. [1] suggested the standard use of sodium citrate, 46.7%, for the filling of haemodialysis catheters in the interdialytic period for the prevention of clotting. In comparison with 5% heparin they showed that 46.7% sodium citrate left the coagulation status unchanged, 1 h after instillation of the anticoagulant. In the case where 5% heparin was used, the coagulation status was altered, as measured by a decreased prothrombin time, and a prolonged partial thromboplastin time. Therefore the anticoagulation lock with citrate was superior in avoiding the risk of bleeding.
We evaluated the efficiency of 30% citrate vs 5% heparin (5000 IU/ml), by aspiration of the catheter lock, just before starting a dialysis session, in chronic haemodialysis patients with a double-lumen or two permanent dialysis catheters. We chose 30% trisodium citrate because this concentration is used in our centre for the regional extracorporeal anticoagulation when dialysing patients at high risk of bleeding [2]. This solution was prepared by our hospital pharmacy.
The comparison was made prospectively, in an open and crossover study design, in 11 patients treated by chronic haemodialysis, three times a week with double-lumen or twin Tesio dialysis catheters. The interval between two dialysis sessions varied between 44 and 68 h.
After the dialysis sessions, each catheter lumen was rinsed with 10 ml of 0.9% NaCl. Then, in part 1 of the study, one lumen was primed with a 30% trisodium citrate solution, the other lumen with 5% heparin. Thus each patient had both catheter locks at the same time, but in different catheter lumina, and served as his own control.
After 10 dialysis sessions, the type of catheter lock was switched in part 2 of this study, for another 10 dialysis sessions. Thus the venous and arterial catheters were compared within the same patient. The volumes used for priming with 5% heparin were those as indicated on the catheters, mostly 2.2 ml, while for 30% citrate 2.5 ml were used.
Before starting dialysis, the catheter lock was aspirated. At that moment an evaluation and score was made:
We used a paired t-test, one-sided, to calculate the P-value of the difference within each study part, and unpaired one-sided t-test to calculate the P-value of the difference between part 1 and 2.
Two hundred and one interdialysis periods could be evaluated, ranging from 7 to 12 dialysis sessions per patient. No occlusion occurred either in the citrate or the heparin arms of this study, and in none of the catheter lumina. There was no need for fibrinolytic therapy during this study. The combined score in the arterial catheter was 140, in the venous catheter 115 (P=0.07, one-side paired t-test). There was no significant difference between the score of the different catheter locks in the same lumen, arterial-citrate vs arterial-heparin (P=0.29), or venous-citrate vs venous-heparin (P=0.28). The combined score of citrate was 127, of heparin 128, (see Table 1).
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We evaluated the use of 30% citrate catheter lock for 34 weeks, in chronic haemodialysis patients. Functional catheter parameters, as venous and arterial pressure, or blood flow during dialysis [3], were not measured during this study, nor was the volume of the catheter thrombus quantified. Infection of permanent dialysis catheters did not occur during this short evaluation period.
Trisodium citrate, 11 or 23%, is compatible with vancomycin, ceftazidime, gentamicin, and penicillin G, and could be used as anticoagulant in antibiotic locks used in vascular access devices [4].
Some patients reported dysgensia for a short period immediately after the injection of citrate. Recently the FDA reported a case of a patient who died shortly after the injection of citrate as catheter lock [5]. This illustrates that the volume of concentrated trisodium citrate for injection as a catheter lock should be limited to the volume of the lumen to be locked, and that the lock should be aspirated before starting dialysis.
In conclusion, our results indicate that for the prevention of thrombus formation in the dialysis catheter during the interdialytic period, 30% trisodium citrate and 5% heparin (5000 UI/ml) are equivalent as a catheter lock in chronic dialysis patients. A 30% citrate solution can be a useful alternative in cases where heparin is not tolerated or is considered to be potentially dangerous.
Acknowledgments
We thank all the nurses from the dialysis ward, for their help in the data collection.
References