What are the lowest doses of low molecular weight heparin for effective and safe hemodialysis in different subgroups of patients?

Plasma levels of enoxaparin oligosaccharides, antifactor-Xa and thrombin generation in patients undergoing haemodialysis

: Low molecular weight heparins are used during haemodialysis for thromboprophylaxis of the dialysis circuit, with plasma antifactor-Xa (anti-Xa) activity used as a surrogate measure for effective anticoagulation. However, this pharmacokinetic parameter does not always correlate with pharmacodynamic effects in patients. The aim of this study was to investigate the relationship between actual plasma levels of the low molecular weight heparins enoxaparin, anti-Xa activity, and global coagulation measurement of thrombin generation during haemodialysis. Blood was analysed from 16 adult patients with end-stage kidney disease at 0, 2, 4 h, and at completion of 31 dialysis sessions where single fixed doses of 20 (n = 3), 40 (n = 16), 60 (n = 6), or 80 (n = 6) mg of enoxaparin (equating to 0.23-1.07 mg/kg) were used as thromboprophylaxis. Plasma enoxaparin oligosaccharides [degree of polymerization (dp)6-dp16] were measured by high-performance size exclusion chromatography, anti-Xa activity by colourimetric assay, and thrombin generation by calibrated automated thrombogram. Plasma enoxaparin fragments were undetectable at the beginning of each dialysis, peaked at 2 h to levels that correlated with dose (r = 0.68, P < 0.001) then remained relatively stable. In contrast, therapeutic anti-Xa levels achieved at 2 h in 18 cases (58%) quickly dropped to only six cases (19%) at the end of dialysis, by which time thrombin generation had also recovered in 81% of patients. Statistical modelling revealed a threshold value of anti-Xa at 0.53 IU/ml that supressed thrombin generation to 15.28% of baseline (P < 0.001). Despite loss of anticoagulant activity in the majority of patients, plasma levels of enoxaparin oligosaccharides remained detectable and relatively unchanged throughout dialysis.

Effect of nadroparin on anti-Xa activity during nocturnal hemodialysis

Background

Nadroparin is used during hemodialysis to prevent clotting of the extra corporeal system. During nocturnal hemodialysis patients receive an increased dosage of nadroparin compared to conventional hemodialysis. We tested whether the prescribed dosage regimen of nadroparin, according to Dutch guidelines, causes accumulation of nadroparin.

Methods

Anti-Xa levels were used as an indicator of nadroparin accumulation. Anti-Xa was measured photometrically in 13 patients undergoing nocturnal hemodialysis for 4 nights a week. Nadroparin was administered according to Dutch dosage guidelines. We assessed anti-Xa levels at 4 time points during 1 dialysis week: before the start of the first dialysis session of the week (baseline), prior to (T1) and after the last dialysis session of the week (T2) and before the first dialysis of the following week (T3).

Results

Patients received 71–95 IU/kg at the start of dialysis and another 50% of the initial dosage after 4 h with a total cumulative dosage of 128 ± 24 IU/kg. Anti-Xa levels increased from 0.017 at baseline to 0.019 at T1 (p = 0.03). Anti-Xa levels were 0.419 ± 0.252 IU/ml at T2 (p < 0.001 vs baseline and T1), whereas anti-Xa levels were not changed at T3 compared to baseline.

Conclusion

Dosing of nadroparin according to Dutch guidelines in patients on nocturnal hemodialysis does not lead to accumulation of nadroparin. We therefore consider the Dutch dosage guidelines for nadroparin an effective and safe strategy.

General significance

This article is the first to present data on anti-Xa activity during nocturnal hemodialysis which is a widely used and potentially dangerous therapy.

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Higher dosages of nadroparin are administered during nocturnal hemodialysis.

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Nadroparin can accumulate which leads to an increased bleeding risk.

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We examined accumulation of nadroparin during nocturnal hemodialysis by measuring anti-Xa levels.

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Accumulation of nadroparin does not occur during nocturnal hemodialysis.

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Dutch guidelines for dosage of nadroparin in nocturnal hemodialysis are safe.