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Critical Care

Open Access

Beneficial use of predilution in reducing the amount of anticoagulation and the occurrence of bleeding during CRRT in critically ill patients: a prospective randomized study

  • PM Honoré1,
  • X Wittebole1,
  • M Lemaire1 and
  • B Pirenne1
Critical Care19982(Suppl 1):P132

Published: 1 March 1998


HeparinPlatelet CountInternal Jugular VeinPartial Thromboplastin TimeActivate Partial Thromboplastin Time


Anticoagulation during CRRT is one of the major issues. We have to take into account three parameters: bleeding occurrence, filter life and filter efficiency. The purpose of the study was to assess prospectively the efficacy of the predilution technique in reducing the amount of anticoagulation during CRRT allowing to use it in critically ill patients at risk for bleeding.


Prospective randomized study.


Fifteen bedded, adult polyvalent intensive care unit in a general hospital.


Twenty consecutive critically ill patients were randomized to have either a predilution set or a post-dilution one during CRRT using the prisma Hospal pump.

Full circuit standard heparinisation was used to achieve an APTT twice baseline. The vascath site was restricted to the right internal jugular vein. The pump speed was kept at 100 ml/min. Filter efficiency was assessed by the haemopermeability index (HPI). The HPI represents the ultrafiltrate flow divided by the transmembrane pressure. The filter efficiency is lost when the HPI has dropped by 70%. Filter life was measured in hours until the circuit clotted off. Data were analysed using non parametric statistical methods. Entry criteria included normal prothrombine time (PT) and normal activated partial thromboplastin time (APTT). The platelet count had to be over 100×109/1. The study was restricted to the first filter of each patient.


The two groups were well matched prior to the therapy for platelet count, haematocrit, oncotic pressure and total calcium measured in the serum.

As shown by the table, the predilution allows a reduction in heparin without imparing the filter life.

To try to understand the mechanism involved, we have also measured the haematocrit, the platelet count, the oncotic pressure and the total calcium in the circuit prior to the filter but after the dilution as shown by the following table.


The predilution technique is a good tool for clinicians in the setting of CRRT in critically ill patients at risk for bleeding. It allows the physician to reduce drastically the amount of heparin used without impairing the filter life and the filter efficiency. The mechanism involved seems to be the reduction of the oncotic pressure rather than other systems involving the calcium.






group n = 10

group n = 10

P value

Median filter life in hours




Median filter efficiency in hours




Symptomatic bleeding




(during the study period)


Median amount of heparin

451 U/h

742 U/h







group n = 10

group n = 10

P value

Median haematocrit




Median platelet count

116 × 109/1

131 × 109/l


Median oncotic pressure

31.3 mmHg

37.2 mmHg


Total calcium

3.8 mEq/l

3.88 mEq/l


Authors’ Affiliations

Department of Intensive Care, St Pierre Hospital, Ottignies, Belgium


© Current Science Ltd 1998