How well does a weight-based unfractionated heparin infusion protocol perform in adult patients during the initial dosing period

Abstract

Background: Unfractionated heparin (UFH) has been used in clinical practice for many years and remains the agent of choice in critically unwell patients, those patients with severe renal dysfunction, and peri-procedurally during cardiac procedures. At King’s College Hospital, a new IV UFH adult guideline was introduced in Oct 2021, recommending a weight-based dosing schedule and a calibrated anti-Xa assay to monitor UFH, in place of APTT. This audit aimed to review how well the new dosing protocol performed in clinical practice during the initial dosing period. Methods: A retrospective audit was conducted of all adult patients commencing UFH infusion from the launch of the guidelines - 13th October 2021 to the 27th of January 2022. In addition to the demographic information on the patients commenced on UFH, the indication and setting of the infusion were recorded, along with the initial dosing received and whether the guidelines were followed. Descriptive statistics were used to analyse the data. Result: Ninety-seven patients were commenced on a UFH infusion during the audit period with a mean age of 60.7 years [SD +/- 14.9] and a mean first anti-Xa result of 0.63 IU/mL [SD = 0.43]. Most patients were in the ICU [n=37, 38%], renal [n=22, 23%], and cardiac ward setting [n= 14, 15%] when the UFH infusion was initiated. Sixty-seven percent [n=65] were male, with 40% prescribed the UFH infusion for venous thromboembolism. The results show that patients who had been prescribed the UFH bolus dose and followed the weight-based UFH guideline [n=16, 41%] were above the target therapeutic range. However, patients treated according to the guideline but not administered a bolus dose [n=38] were more likely to have the first anti-Xa level in the range [n=27,71%]. Female patients were more likely to be above the range [n=11, 34%] compared to male patients [n=12, 18%]. Conclusion: The new protocol using a weight-based dosing schedule and anti-Xa performed well in ensuring therapeutic levels of anticoagulation with UFH. The findings suggest that patients who were not administered the bolus and followed the UFH infusion guideline were more likely to achieve the anti-Xa therapeutic range. We have now amended our UFH guideline from mandating the bolus to considering the administration of a bolus if clinically indicated. We plan to re-audit, following this change