Oral anticoagulation in the hospital: analysis of patients at risk

Abstract

Warfarin is one of the most commonly used medications associated with adverse events. Warfarin therapy is often initiated or continued in the hospital, yet hospitalization increases the risk of poor anticoagulation control with warfarin. To help understand this, we retrospectively reviewed the records of patients admitted to our hospital during a 6-month period who were given at least one dose of warfarin. To explore factors that may have contributed to poor anticoagulation control, we compared characteristics of patients with an international normalized ratio (INR) ≥ 5 at some point during hospitalization with those of a group of matched controls who also received warfarin and had INR <5. Among the 35 patients identified who had an INR ≥ 5, concomitant use of antibiotics was more common than among 105 matched controls; improper warfarin dosing also appeared to contribute to the high INRs. These findings indicate possible targets for intervention to improve patient safety.

Inpatient warfarin management: pharmacist management using a detailed dosing protocol

“…Moreover, this study showed that our inpatient detailed dosing protocol reduced the number of patients with INR higher than 5, a level that has been shown to be associated with increased risk and complications [4]. This result is even more notable considering that the intervention patients were more likely to be receiving antibiotics, which have been shown to interact with warfarin and increase the risk of levels out of the therapeutic range [3].…”

“…Prior studies have shown that poor monitoring can worsen control [3]. Even if this lack of monitoring is a contributing factor for poor control, the dosing protocol allows this oversight using existing pharmacy resources, which is an advantage to hospitals in the face of rising costs.…”

“…Warfarin dosing and monitoring are a critical part of this mandate, as studies have shown that at least 10% of inpatients are given warfarin while hospitalized [3]. Physicians may have available dosing nomograms and order sets to guide warfarin management but may fail to engage them or alter therapy without prompting.…”

“…Although these are common practices, studies have shown that hospitalization can worsen anticoagulation control with warfarin [2], as measured by the international normalized ratio (INR). Medication interactions, primarily with antibiotics, as well as acute illness, lack of daily laboratory monitoring, and incorrect dosing can all affect control and result in a nontherapeutic INR [3]. In addition, dietary changes, comorbid conditions, and medications other than antibiotics can cause fluctuations in INR results in hospitalized patients, exposing them to risks of thrombosis or bleeding [4].…”

“…After studying the reasons behind poor warfarin anticoagulation control in our hospital [3], we initiated a quality improvement project with the goal of increasing the percentage of hospitalized patients who maintained a therapeutic INR. We postulated that a detailed warfarin dosing protocol administered by pharmacists with minimal physician oversight could significantly reduce the proportion of hospitalized patients with a supratherapeutic INR during their hospitalization.…”