The optimized anticoagulation strategy in prolonged hemodialysis.

Background: During extended (nocturnal) hemodialysis (ENHD), the dose of low-molecular-weight heparin (LMWH) can be administered as a single injection or as a divided dose over different time points. Our hypothesis was that a single injection might be sufficient to maintain dialyzer fiber patency. In addition, we investigated whether the biochemical clotting parameter anti-Xa accurately predicts fiber blocking.

Methods: Our hypothesis was tested in 20 stable patients on ENHD in a random cross-over setting during two consecutive midweek sessions. The regular total dose of LMWH (i.e. enoxaparin, Clexane® 40-100  mg, Sanofi, Belgium) was either given (i) in a single injection at the dialysis start or (ii) divided over two injections, at the start and halfway the dialysis session. Blood samples were taken from the arterial blood line at different time points to determine plasma anti-Xa activity levels. Post-dialysis, the rinsed and dried hemodialyzers were scanned with a reference micro-computed tomography (µCT) scanning technique, and non-blocked fibers were counted in a central cross-section of the dialyzer outlet potting (ImageJ, NIH, USA).

Results: The percentage of open fibers in the dialyzers after a single injection of LMWH [91 (61-96)%] versus divided administration [94 (79-98)%] was not different. Time averaged anti-Xa activity levels were clinically not significantly different between both sessions. Anti-Xa activity levels correlated with the administered anticoagulation doses normalized for body weight, but not with the percentages open fibers in the dialyzers.

Conclusion: Our results indicate that there is no need to administer enoxaparin over two injections for ENHD up to 8 h. The usefulness of monitoring anti-Xa levels to predict fiber patency, assessed by µCT, can be questioned, but further clinical trials are needed.