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Richard H. White, MD; Hong Zhou, PhD; Linda Woo, MD; Dennis Mungall, PharmD

Arch Intern Med. 1997;157(21):2468-2472.

Abstract
Background
There is a significant direct relationship between steady-state intravenous heparin dose requirements and total body weight. Less is known about whether sex, age, clinical diagnosis, and the thromboplastin used to measure the activated partial thromboplastin time (aPTT) affect heparin dose requirements.

Methods
Four cohorts of patients treated with intravenous heparin were gathered from 3 hospitals: 2 cohorts with deep vein thrombosis (DVT) and 2 cohorts with coronary artery disease (CAD). For each clinical diagnosis, half the patients were monitored using one aPTT reagent and the remainder were monitored using a second reagent. Heparin doses and aPTT measurements were recorded, and the dose necessary to achieve an aPTT ratio of 2.0 was calculated using a computer software program.

Results
We analyzed the records of 340 patients: 165 with DVT and 175 with CAD. Using analysis of variance, there was a significant difference in the steady-state heparin requirements among patients with DVT compared with patients with CAD (P<.001). For each clinical diagnosis, the use of a different thromboplastin reagent did not affect heparin dose requirements (P>.42). Linear regression modeling disclosed that the steady-state heparin dose for patients with DVT was a function of weight plus an effect modifier involving weight and age, whereas for patients with CAD there was only a weak relationship with weight.

Conclusions
Steady-state heparin dose requirements were significantly different in patients with DVT compared with patients with CAD, suggesting that different dosing nomograms are needed for each condition. For patients with DVT, the accuracy of the initial heparin dose estimate may be improved by considering the patient's age and weight.

Arch Intern Med. 1997;157:2468-2472

Author Affiliations
From the Division of General Medicine (Drs White and Zhou) and the Departments of Statistics (Dr Zhou) and Medicine (Dr Woo), the University of California, Davis, Sacramento; and the Department of Family Medicine, Tallahassee Memorial Hospital, Tallahassee, Fla (Dr Mungall).

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