Unfractionated heparin (UFH) infusions continue to have an important role in hospitalised patients but treatment protocols are often poorly implemented, an audit in western Sydney has concluded.

In a poster presented at HAA, Dr Gajan Kailainathan and colleagues said that despite an increasing choice of anticoagulants, UFH is important in acute coronary syndromes, in acute venous thromboembolism among patients with excessive bleeding risk or renal impairment, and in peri-procedural anticoagulation.

“Attributes of UFH include a rapid onset of action and clearance, ability to monitor its activity through widely available assays, ability to rapidly reverse its activity, a lack of substantial renal metabolism which allows it use in renal insufficiency, and extensive clinical experience,” they said.

“Despite these advantages, potential morbidity and mortality is often overlooked.”

Due to the unpredictable anticoagulant response, heparin infusion protocols are used to guide dose adjustments based on the activated partial thromboplastin time (aPTT).

A lack of understanding of UFH pharmacology and poor compliance with infusion protocols could lead to an increased risk of thrombosis from under-dosing, or bleeding from over-dosing.

The team retrospectively audited UFH use in 12 patients in Blacktown District Hospital, checking the timing of aPTT checks, percent of therapeutic aPTTs and appropriateness of dose adjustments. They reviewed case notes to establish reasons for deviations from the protocol.

About one in three aPTT samples – 37% – were not collected at the recommended time after a dose change. There were 67% of all aPTT measurements which were outside the therapeutic range, with an approximately equal incidence of sub-therapeutic and supra-therapeutic readings.

Minor bleeding occurred in two patients but it was not associated with supra-therapeutic aPTTs.

Only 51% of dose adjustments were consistent with protocol recommendations, and there were unexplained changes in infusion rates which were not adequately documented in the notes.

“Our findings were consistent across treatment locations – cardiac step-down, coronary care, high dependency and ICU,” they said.

Factor contributing to the suboptimal use of UFH included delays in the RMO attending the patient to collect the aPTT or residents ordering aPTTs simply as part of a standard pathology collection round.

“This is likely due to a busy workload. However, we feel a poor understanding of heparin pharmacokinetic and a lack of appreciation of the implications of sub- or supra-therapeutic aPTTs compound this issue,” they said.

“Greater input from senior clinicians is warranted in these situations, and quality measures need to be implemented to mitigate any risk associated with UFH misuse.”