Audit of Enoxaparin Thromboprophylaxis Dosing Following Hip Surgery in Older Patients According to Weight and Renal Function

Introduction

Venous thromboembolism is a significant cause of morbidity and mortality following orthopaedic surgery. Older patients with hip fractures represent a particularly vulnerable population. The National Institute for Health and Care Excellence (NICE), British National Formulary (BNF), and local trust guidelines recommend prophylactic post-operative enoxaparin doses with body weight and renal adjustment. This audit aims to assess compliance with these guidelines following hip surgery.

Methods

A retrospective two-cycle audit was undertaken involving 35 consecutive patients admitted under the orthogeriatric team following hip surgery (hemiarthroplasty, internal fixation, and revision procedures) over a one-month period. Patients receiving therapeutic anticoagulation or alternative thromboprophylaxis were excluded. Compliance with weight and creatinine clearance (CrCl) adjusted enoxaparin dosing was assessed. Following the first cycle, results were presented to orthopaedics and relevant clinical teams, with education and prescribing reminders encouraging weight documentation and CrCl calculation before prescription.

Results

Results showed an improvement in correct prescriptions from 29/35 patients (83%) in the first cycle to 31/35 (89%) following intervention. In the first cycle, six patients were incorrectly dosed with one underdosed and five overdosed. Two of six errors (33.3%) resulted from failure to adjust dosing for CrCl <30 mL/min and four (66.7%) were due to inappropriate weight adjustment. Five of these errors were subsequently identified and corrected. In the second cycle, four patients were initially overdosed, with one error related to low CrCl and three to weight. All prescribing errors were identified and corrected within 72 hours.

Conclusion

Targeted education and prescription reminders improved compliance with enoxaparin thromboprophylaxis dosage guidelines and achieved a 100% correction rate for errors. However, ongoing interventions are required to encourage prompt weight documentation and CrCl calculation minimising dosing errors and therefore improving patient safety.