Background and importance In our orthopaedic surgery centre, prescribers seem to use different dosages of enoxaparin for the prevention of the thromboembolic risk for obese patients. Systematically, the dosage is adapted to renal function, but there are no guidelines for obese patients.

Aim and objectives The aim was to analyse the prescribing practices to create an internal protocol.

Material and methods This was a retrospective study from 1 January 2020 to 28 February 2020 of every enoxaparin prescription for a preventive dosage in orthopaedic surgery. We compared enoxaparin’s dosage with different criteria: sex, age, weight, body mass index (BMI), glomerular filtration flow, surgical and medical history, chronic treatment, surgical indication and prescribers.

Results We included 517 patients (table 1).

Every patient with a dosage higher than 4000 IU (35/517) weighed >80 kg. Among them, 7 patients (19.4%) had a BMI >40 kg/m². These patients received 4000 IU of enoxaparin twice a day or 6000 IU in one administration. 20 of 517 patients were of low weight (<45 kg for women and <57 kg for men), and among them 6 (30%) received <4000 IU/day. Apart from renal function, no other criteria influenced the dose of enoxaparin. There was a disparity in dosages between prescribers. Of 19 prescribers, 7 (36.8%) occasionally, and 1 systematically, increased the dose of enoxaparin for weights >80 kg and BMI <40 kg/m². No thrombosis or haemorrhage occurred for dosages >4000 IU/day.

Conclusion and relevance European studies are based only on BMI or weight: increased dosage of enoxaparin for BMI higher than 40 kg/m² and more or less weight higher than 100 kg. The heterogeneity of prescriptions between prescribers and by prescribers highlights the lack of consensus. Adapting the dosage for a weight >80 kg does not seem appropriate because it includes non-obese patients with an increased risk of bleeding. Work in tandem with anaesthesiologists is underway to harmonise practices in our centre.

References and/or acknowledgements

1. Tzu-Fei Wang, et al. Efficacy and safety of high dose thromboprophylaxis in morbidly obese inpatients.

2. Freeman A, et al. Prevention of venous thromboembolism in obesity.

Conflict of interest No conflict of interest