Convenience Over Evidence? Heparin Nomograms Vs Usual Care at an Academic Medical Center

Meeting: Hospital Medicine 2012, April 1-4, San Diego, Calif.

Abstract number: 97597


Though there is little evidence examining the use of intravenous heparin nomograms, concerns about difficulty maintaining therapeutic aPTT levels have led to the adoption of dose–adjustment nomograms at many hospitals. Nomograms can promote standardized practice and add convenience as they allow nursing staff to adjust the rate without requiring a physician to check lab values and contact the nurse. However, each hospital needs to develop its own nomogram as the target therapeutic range aPTT varies depending on the reagents used by each lab. Institutions must also update the nomogram as needed when reagents change. Due to these limitations the efficacy and safety of heparin nomograms is unclear.


Our institution utilizes a heparin dose–adjustment nomogram on certain units, including the Stroke, Cardiac Telemetry, and Cardiothoracic Intensive Care Units (Nomogram wards). Other wards do not utilize a nomogram and consist of General Medicine, Cardiac Telemetry, and Vascular Surgery Units (Usual Care wards). For the Nomogram wards, the unfractionated heparin (UFH) infusion rate was initiated, aPTT monitored, and the rate adjusted according to a nomogram by the nurse caring for the patient. On the Usual Care wards, the frequency of monitoring and all rate adjustments were made at the clinician’s discretion. We performed an administrative database review to compare the aPTT values for the Nomogram Group and the Usual Care wards. Data was collected for the year 2010. All aPTT values drawn on the day patients were administered IV UFH were included. The data was grouped into ranges of aPTT considered subtherapeutic (<60 secs), therapeutic (60–100), and supratheraputic (>100). We then calculated the percent of aPTT values in each of these ranges for the two groups.


We examined a total of 614 aPTT values, 424 in the Usual Care and 190 in the Nomogram wards (see Table 1). Nomogram wards were less likely to have subtherapeutic values (48% vs 61%, P < 0.01) and more likely to have aPTT values in the supratherapeutic range (23% vs 13%, P < 0.01). There was no difference in the number of aPTT values in the therapeutic range in the two groups (29% vs 26%) (P = NS).


Wards using an IV heparin dose–adjustment nomogram were less likely to have subtherapeutic aPTT values than wards without a nomogram at the expense of more supratherapeutic values. Though the non–randomized design and lack of information on clinical outcomes prevent any definitive conclusions, our results suggest clinicians should be cautious when using heparin nomograms. Hospitals should be aware of the lack of data on the safety of heparin nomograms, adjust their target range when required based on local laboratory revisions, and periodically assess nomogram performance.

Table 1Nomogram Versus Usual Care Ward aPTT Values

aPTT Range Usual Care (N= 424) Nomogram (N= 190) P value
<60 259 (61%) 91 (48%) <0.01
60–100 112 (26%) 55 (29%) 0.51
>100 53 (13%) 44 (23%) <0.01

To cite this abstract:

Dunn A, Rule E, Reyna M. Convenience Over Evidence? Heparin Nomograms Vs Usual Care at an Academic Medical Center. Abstract published at Hospital Medicine 2012, April 1-4, San Diego, Calif. Abstract 97597. Journal of Hospital Medicine. 2012; 7 (suppl 2). Accessed March 28, 2020.

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