Pharmacodynamics of Unfractionated Heparin During and After a Hemodialysis Session
Received 30 May 2007; accepted 26 December 2007.
Background
Anti-Xa activity is used as a clinical guide to anticoagulation with heparin, but heparin dosing regimens for hemodialysis were established before anti-Xa assays were developed; thus, the optimal regimen for heparin dosing was not determined. The aim is to confirm the interesting characteristics of unfractionated heparin pharmacokinetics for hemodialysis anticoagulation, provide insight into the hemorrhagic risk of hemodialysis patients, and determine the dose of unfractionated heparin and its adequate mode of administration.
Study Design
Cross-sectional study of the pharmacokinetics of unfractionated heparin performed during and after a 4-hour midweek hemodialysis session.
Setting & Participants
35 long-term hemodialysis patients at the Sainte-Marguerite Unit of the Marseille University Hospital, Marseille, France.
Predictor
Hemodialysis anticoagulation with continuous unfractionated heparin infusion at a dose of 50 IU/kg/session (25 IU/kg/h during the first hour, 12.5 IU/kg during the second and third hours, and stop during the last hour).
Outcome & Measurements
Anti-Xa activity was monitored during the 10 hours after the beginning of the hemodialysis session. Levels of 0.3 to 0.7 IU/mL are considered sufficient for anticoagulation. Pharmacokinetics was determined by using a population approach (nonlinear mixed-effects modeling). The final model and corresponding parameter values (including interindividual and residual variability) were used to simulate 1,000 replicates.
Results
No case of clotting was recorded. A pharmacokinetic model with 1 compartment and first-order elimination best fitted the data. Terminal half-life was 54 minutes. Median anti-Xa activities were 0.55 IU/mL at peak, 0.25 IU/mL at end of the 4-hour session, and less than 0.1 IU/mL at 90 minutes after the session. We simulated a continuous infusion of the dose of 50 IU/kg for 1, 2, 3, and 4 hours. Peak values were 1.1, 0.8, 0.6, and 0.5 IU/mL, respectively. Values at the end of the session were 0.12, 0.18, 0.3, and 0.5 IU/mL, respectively. Values became less than 0.1 IU/mL at 15, 60, 105, and 120 minutes after the session, respectively.
Limitations
Interindividual variability in unfractionated heparin pharmacokinetics.
Conclusions
Unfractionated heparin administered by means of a 3-hour continuous infusion for hemodialysis anticoagulation provided an efficient and safe effect that quickly disappeared after the end of the session.
1Centre de Néphrologie et de Transplantation Rénale Hôpital de la Conception, Assistance Publique-Hôpitaux de Marseille, Marseille, France
2Laboratoire de Pharmacologie Médicale et Clinique, Faculté de Médecine, Marseille, France
3Laboratoire Central Hôpital Sainte-Marguerite, Assistance Publique-Hôpitaux de Marseille, Aix-Marseille Université, Marseille, France.
Address correspondence to Philippe Brunet, MD, Centre de Néphrologie et de Transplantation rénale, Hôpital de la Conception, 147 Bd Baille, 13005 Marseille, France.
ABSTRACT