In this episode, I’ll discuss using thrombin time to transition patients from dabigatran to unfractionated heparin.
When a hospitalized patient on chronic dabigatran therapy for VTE treatment develops acute kidney injury, they are typically transitioned to a continuous heparin infusion. However deciding when to stop the dabigatran and when to start the heparin is complicated, as anti-Xa or PTT levels are not accurate for the purpose of determining when the anticoagulant effects of dabigatran have started to diminish. The prescribing information recommendations for waiting 24 hours after the last dose of dabigatran before switching to heparin in patients with a creatinine clearance below 30 mL/min are empiric and do not take patient specific factors into account.
As the thrombin time has been studied as a potential marker of residual dabigatran anticoagulant activity, a group of authors has published a 2-patient case series describing their experience using thrombin time to transition patients from dabigatran to heparin.
The first patient was a 77 year old male admitted for respiratory distress from COVID-19 infection who was taking dabigatran 150 mg twice daily prior to admission. The patient had acute kidney injury with a serum creatinine value about 50% above baseline. The thrombin time assay from about 18 hours after the last dabigatran dose was above the laboratory’s upper limit for detection. At 36 hours after the last dabigatran dose the thrombin time was measured at 104.8 seconds. Because the patient’s kidney function was also improving at this time, the patient was transitioned to an IV heparin infusion without a bolus. After 5 days of heparin infusion it was held due to what was thought to be a GI bleed but was later determined to be rectal bleeding secondary to hemorrhoids. Heparin was resumed for another 5 days before the patient was transferred to hospice care. The patient did not experience a thrombotic event.
The second patient was an 89 year old female admitted for acute respiratory failure who was taking dabigatran 150 mg twice daily prior to admission. The patient had acute kidney injury with a serum creatinine value about 70% above baseline. The patient’s thrombin time remained above the laboratory’s upper limit of detection for 53 hours until the first reading within range which was 119.4 seconds. A heparin infusion was started without a bolus. About 24 hours after initiation of heparin, the patient’s hemoglobin decreased from 7.2 g/dL to 6.4 g/dL. Heparin was continued with a lower PTT target, the patient received a transfusion, but there was no evidence of overt bleeding. The patient was eventually transitioned to warfarin and discharged to a nursing facility.
The authors opinion is that thrombin times above the upper limit of detection can reasonably be assumed to indicate residual dabigatran activity and when the thrombin time drops into the detectable range, transitioning to IV heparin is appropriate to consider. Once the thrombin time comes into the detectable range, the authors stop checking thrombin time under the assumption that this point represents evidence of adequate dabigatran clearance. While research should be done to explore the safety and efficacy of a thrombin time guided transition from dabigatran to IV heparin, this case series represents a potential approach in situations where a dabigatran assay is not available in a clinically reasonable timeframe.
The article in this episode is a selection from my Hospital Pharmacy Academy’s weekly literature digest. Have you ever felt like your physician colleagues are one step ahead of you with new literature developments? Every week, Academy members are provided a summary curated and explained by me of the top hospital pharmacy-related articles published that week from over 20 major journals and sources to save you time and keep you up to date with the literature. To get immediate access, go to pharmacyjoe.com/academy.
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