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Ann Intern Med. 1993 Jul 15;119(2):104-9.

Establishing a therapeutic range for heparin therapy.

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1
McMaster University Medical Center, Hamilton, Ontario, Canada.

Abstract

OBJECTIVE:

To compare two methods of determining a therapeutic range of activated partial thromboplastin time (aPTT) results.

DESIGN:

Cohort studies.

SETTING:

Referral teaching hospital.

PATIENTS:

Inpatients who received unfractionated heparin intravenously for venous thromboembolic disease.

MEASUREMENTS:

A therapeutic range determined by aPTT ratios of 1.5 to 2.5 times the control value as compared with a therapeutic range determined by protamine titration heparin levels of 0.2 to 0.4 U/mL.

RESULTS:

For all aPTT reagents studied, a ratio of 1.5 times the control value is much less than a minimum protamine titration heparin level of 0.2 U/mL. Various manufacturers' aPTT reagents and reagent lots from the same manufacturer show considerable variation in response to heparin and therefore have different therapeutic ranges.

CONCLUSIONS:

A different dose of heparin would be required to produce an aPTT ratio of 1.5 times the control value, depending on the reagent used. Establishing a therapeutic range for aPTT results using protamine titration heparin levels of 0.2 to 0.4 U/mL as a reference standard is practical and compensates for the variable response of aPTT reagents to heparin.

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[Indexed for MEDLINE]

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