22 Point prevalence study of therapeutic anticoagulation dosage based on renal function in an older population

Abstract

Abstract Background Older patients (age > 65 years) are frequently prescribed Therapeutic Anticoagulation (TA), most commonly for Atrial Fibrillation (AF) and Venous Thrombo-Embolism (VTE). Importantly, advanced age (> 80 years) increases the risk of anticoagulation-associated major haemorrhage. Methods A point prevalence observational study of all patients admitted to a Post-Acute Care Unit (PACU) was undertaken. In addition to demographic information, prescribing data and indication for TA was collected. Laboratory data collected included serum creatinine (sCr) and estimated glomerular filtration rate (eGFR) using the MDRD formula. Dosing of anticoagulation based on renal function, age and weight was assessed and compared to the Health Products Regulatory Authority (HPRA) recommended guidelines. Results 70 patients were admitted to PACU on the day of study. 34.3% (n = 24) were prescribed TA, these patients were older (age 83.7 ± 7.9 years) and majority were male (M:F = 66%:34%), median weight was 60.45 kg (range = 41.3–91.6 kg). Indications for anticoagulation were AF 71% (n = 17), VTE 17% (n = 4), mixed AF/VTE 8% (n = 2) and mechanical valve replacement 4% (n = 1). Apixaban was the most commonly prescribed anticoagulant (66%, n = 16), followed by Rivaroxaban (12.5%, n = 3), Dabigatran (8%, n = 2), Enoxaparin (8%, n = 2) and Warfarin (4%, n = 1). In 66.7% (n = 16), the CrCl resulted in lower renal function than the eGFR, and in over 40% of cases the difference resulted in a dose adjustment of TA prescribed. Overall, CrCl was <50 mL/min in 58.3% (n = 14); CrCl 30–50 mL/min in 33% (n = 8), CrCl 15–29 mL/min in 21% (n = 5) and CrCl <15 mL/min in 4% (n = 1). In 25% of patients (n = 6), the dose of TA was incorrect with lower CrCl more likely to result in dose reduction of TA. Conclusion TA is an important treatment in older patients and this study showed that reduced renal function is likely to result in reduced dosing, which may produce a subtherapeutic response.