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Monitoring heparin treatment with the APTT: the effect of methodological changes on the APTT
J W Krulder1, F J van der Meer, E Briët
1Department of General Internal Medicine, University Hospital Leiden, Netherlands.
Objective:
To assess the effect on the desired activated partial thromboplastin time (APTT) of altered practice in the laboratory control of heparin treatment.
Methods:
Descriptive study of the number of APTTs in the desired range (DR) in 1987 (historical controls) and in 1992/1993. In the latter period, four changes in the implementation of heparin treatment took place: another coagulation analyser was used, laboratory control was intensified with a nomogram as guideline, and the DR was changed form 90-120 to 45-60 s. Furthermore, a standard heparin solution of 417 U/ml was supplied by the hospital pharmacy.
Results:
The total amount of APTTs in the desired range increased from 19% in 1987 to 46% in 1992/1993, and the DR was reached in 1987 in 1 day by 14%, and in 1992/1993 by 48% of patients. The mean daily heparin dose was higher in 1992/1993 (34.1 * 1000 U, 95% CI 33.4-34.8) than in 1987 (32.3 * 1000 U, 95% CI 31.5-33.0). The starting dose of heparin of 400 U/kg during the first day, following an initial bolus injection of 70 U/kg, was correct in 44% of patients, too low in 46%, and too high in 10%.
Conclusions:
The new policy in the laboratory control of heparin treatment resulted in an increased number of APTTs in the DR, and a shorter time to reach this.