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Preventing Anticoagulant-Related Bleeding
- C. Seth Landefeld, MD; and
- Philip A. Anderson, MD
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IN RESPONSE:
Dr. Davidson asks: What is the optimal range of the APT for an individual patient treated by continuous infusion of heparin? The question is important because low APT have been associated with bleeding [1, 2]. Unfortunately, available data do not provide a definitive answer.
Hirsh and colleagues [4] reported that 1) heparin levels of 0.2 to 0.4 U/mL by protamine titration achieved a full antithrombotic effect, as indicated by inhibition of fibrinogen accretion; 2) the APT value associated with a given heparin concentration varies directly with the patient's baseline APT; and 3) a heparin level of 0.3 U/mL correlated to an APT approximately twice the patient's baseline value. These observations led to the conclusion that “ideally, the patient's pretreatment blood sample should be used to calculate the ratio of the heparin effect” [4]—a recommendation that we think is reasonable, but that differs from usual practice [2, 3]. Also, before beginning our study[5], we obtained data from our hospital's clinical laboratory indicating that APT 1.5 to 2.5 times the patient's baseline value correlated with heparin levels of 0.2 to 0.5 U/mL.
We heartily agree with Dr. Davidson that “underdosing” is to be avoided in starting heparin therapy. We disagree, however, that the literature indicates that it is better to compare the APT with a mean laboratory control value than to the patient's baseline value, or vice versa. In the use of heparin, it is most important to recognize that the responsiveness of the reagents used in the APT test varies widely and that an APT equivalent to a heparin level of 0.2 to 0.4 U/mL should be attained quickly and should be maintained [2].
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
•Include no more than 300 words of text, three authors, and five references
•Type with double-spacing
•Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.
Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
Annals welcomes electronically submitted letters.
- Copyright ©2004 by the American College of Physicians
