Measuring of the heparin leakage into the circulation from central venous catheters--an in vivo study.

Background: A catheter lock with a highly concentrated heparin solution is often used to maintain its patency. The result of the in vitro study shows a significant catheter leakage that occurs after locking the catheter. The goal of this study is to develop a model to measure the catheter leakage in vivo and test it on various kinds of catheters.

Methods: Twenty-four patients with central venous dialysis catheters were examined. After the 48-h interdialytic period, we aspirated the contents of the catheter lumen for analysis. We simultaneously took a sample of the peripheral blood for analysis. In the second part of the test, instead of taking the sample after 48 h, we took it after 10 min. Based on the difference in haematocrit in those two samples, we were able to determine the amount of heparin that remained in the catheter, and indirectly, the amount of heparin that leaked out of the catheter.

Results: Using the lock volumes indicated on the catheter by the manufacturer, the early leakage is significantly higher in nontunnelled catheters compared to tunnelled Hemoflow and Ash Split catheters (P = 0.05). There is no significant statistical difference in the early leakage between Ash Split and Hemoflow catheters. The late leakage is significantly higher in nontunnelled catheters compared to Hemoflow and Ash Split catheters (P = 0.05). There is no significant statistical difference in the total leakage between Ash Split and Hemoflow catheters.

Conclusion: We present a model that enables the measurement of the catheter leakage in vivo. We applied the model on three kinds of catheters and concluded that both early and late leakages are significantly higher in nontunnelled catheters compared to Hemoflow and Ash Split tunnelled catheters. Our results show that the so-called early leakage measured in vivo is significantly lower compared to the results from in vitro studies. Further research is necessary to determine the amount of leakage volume for different kinds of catheters and to determine the exact leakage dynamics of lock solutions in vivo.