Abstract
This study evaluates three warfarin dosing algorithms (Kimmel, Dawson, High Dose ≥ 2.5 mg) for hospitalized older adults. A random selection of 250 patients with overshoots (INR ≥ 5 after 48 h of hospitalization) and 250 patients without overshoots were accessed from a database of 12,107 inpatients ≥ 65 years treated with chronic warfarin during hospitalization between January 1, 2014 and June 30, 2016. Algorithms were retrospectively applied to patients 2 days prior to overshoots in the overshoot group, and 2 days prior to the maximum INR reached after 48 h of hospitalization in the non-overshoot group. Patients were categorized as overdosed or not overdosed and compared using descriptive statistics. Logistic regression modeling determined predictors for overshoots. There was no significant difference between overdose and non-overdose groups for progressing to overshoots by the Kimmel (51.0% vs. 48.7%, p = 0.67) or Dawson (48.5 vs. 57.9%, p = 0.19) algorithms. The Low Dose Group (≤ 2.5 mg) was significantly more likely to experience an overshoot than the High Dose Group (56.6% vs. 45.5%, p = 0.04). The Low Dose Group was more likely to be older (81.4% vs. 71.1%, p = 0.02), female (63.5% vs. 49.8%, p = 0.02), weigh less (71.3 ± 21.9 vs. 79 ± 23.1, p = 0.002), and be prescribed amiodarone (16.6% vs. 8.1%, p = 0.01). While none of the algorithms predicted overshoots in logistic regression modeling, weight over 70 kg and black race remained protective. The High Dose Algorithm revealed that providers appropriately gave lower doses to patients at highest risk for warfarin sensitivity. Future studies are needed to investigate tools for inpatient warfarin dosing in older adults.
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Acknowledgements
The authors would like to acknowledge the Center for Health Innovations and Outcomes Research at Northwell Health for their support.
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The authors would like to acknowledge the New York State Empire Clinical Research Investigator Program (ECRIP) and the Center for Health Innovations and Outcomes Research at Northwell Health for their support.
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Appendices
Appendices
Appendix 1: Kimmel’s clinical dose-revision algorithm [15, 16]
1/7 × | exp | [(2.81602 | |
− | 0.00590 × age in years | ||
+ | 0.07123 × black race | ||
+ | 0.17675 × body surface area in m2 | ||
− | 0.16759 × diabetes | ||
− | 0.22844 × stroke | ||
− | 0.11137 × amiodarone use | ||
− | 0.25487 × fluvastatin use | ||
+ | 0.27815 × target INR | ||
− | 0.76679 × ln INR | ||
+ | 0.03471 × dose−2 | ||
+ | 0.03047 × dose−3 | ||
+ | 0.01929 × dose−4] |
Appendix 2: Dawson’s continuation of warfarin therapy protocol [10]
Today’s INR | Today’s dose |
|---|---|
< 1.7 | Increase by 50% |
1.7–1.9 | Increase by 30% |
2.0–3.0 | No change |
3.1–3.5 | Decrease by 10% |
3.6–4.4 | Decrease by 30% |
> 4.5 | Hold dose |
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Cohen, J.L., Thompson, E., Sinvani, L. et al. Assessment of warfarin algorithms for hospitalized adults: searching for a safe dosing strategy. J Thromb Thrombolysis 48, 570–579 (2019). https://doi.org/10.1007/s11239-019-01902-0
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DOI: https://doi.org/10.1007/s11239-019-01902-0