Prevalence of risk factors for venous thromboembolism and aspirin resistance in Australian patients undergoing total hip and knee arthroplasty.

INTRODUCTION: Aspirin is used for venous thromboembolism (VTE) prophylaxis after total hip and knee arthroplasty (THA/TKA). However, its efficacy is unclear in patients with multiple VTE risk factors and at risk of aspirin resistance (AR). BACKGROUND AND AIMS: To determine the prevalence of risk factors for VTE and AR in patients after THA/TKA and to determine the relationship between risk factors and drugs prescribed for thromboprophylaxis. METHODS: A retrospective cohort study of elective-THA/TKA in six Australian hospitals over a 1-year period. Medical records were manually reviewed to determine demographics, thromboprophylaxis regimen and presence of risk factors. The relationship between individual and cumulative risk factors with the thromboprophylaxis regimen was determined. RESULTS: In total, 1011 patients were included with a mean (SD) age of 65.9 (±11.0) years, and 56.4% were female. The five most prevalent risk factors were obesity (59.1%), age ≥65 years (58.2%), hypertension (45.3%), dyslipidaemia (35.9%) and diabetes (19.7%). Most patients had ≥1 risk factor for VTE (93.6%) and AR (93.6%), with 49.0% and 35.0% having ≥3 concurrent VTE and AR risk factors, respectively. The only significant relationship between risk factors and drugs was diabetes (P < 0.01). Rivaroxaban was more commonly used as the number of concurrent VTE risk factors increased (P < 0.05). CONCLUSION: Patients had a high prevalence of VTE and AR risk factors, suggesting aspirin may not be beneficial in many patients. Only diabetes was linked to the selection of thromboprophylaxis. Patients who received rivaroxaban had a greater average number of VTE risk factors. Guidelines should promote individualised prescribing in higher-risk patients.

Evaluation of the Quality and Safety of Venous Thromboembolism Prophylaxis Among Gastroenterology Inpatients at a Tertiary Hospital in Australia.

Background and objective: Hospital acquired venous thromboembolisms (VTEs) are common and preventable. The Queensland Health VTE prophylaxis guidelines, developed in 2018, provide guidance for risk assessment, and prescribing of anticoagulation for prophylaxis and treatment of hospital inpatients. Currently, there are limited recommendations for gastroenterology patients. This study investigated the completion of VTE risk assessments, and the appropriateness of VTE prophylaxis regimens, in accordance with Queensland Health guidelines for gastroenterology patients. The quality and safety of VTE prophylaxis regimens was assessed based on their VTE risk and bleeding risk. Method: A retrospective study was conducted by obtaining a random sample of gastroenterology patients admitted to a tertiary Australian hospital, from 1st May 2019 and 1st May 2020, to determine the compliance of VTE risk assessment and thromboprophylaxis prescribing with state-wide VTE guidelines. The quality and safety of thromboprophylaxis was evaluated using the modified Caprini and HASBLED scores, and subsequent thromboprophylaxis-related complications. Results: Of the 94 patients reviewed, 68 did not have contraindications to thromboprophylaxis. Of these 68 patients, 32 (47%) had no VTE risk assessment recorded in their clinical records and were not prescribed any thromboprophylaxis during the hospitalization. There was no significant difference between thromboprophylaxis prescribing for patients with low VTE risk, compared to moderate to high VTE risk (P = .075). There was a trend for decrease in thromboprophylaxis prescribing as HASBLED bleeding risk score increased, and patients with moderate-high bleed risk were less likely to be prescribed thromboprophylaxis (P = .006). There were no thromboprophylaxis related complications identified. Conclusion: It is essential that all patients have a clearly documented risk assessment and are prescribed thromboprophylaxis according to best practice guidelines. The prescription of venous thromboembolism prophylaxis should continue to be individualized, with each patient assessed holistically.

Platelet Function Assays for the Diagnosis of Aspirin Resistance.

Aspirin, an antiplatelet drug, is commonly used at low doses for numerous indications, including prophylaxis of cardiovascular, neurovascular, and venous thromboembolic events. Due to review articles suggesting that aspirin resistance may result in poorer outcomes, interest in assessing platelet function is increasing. Despite this, platelet function tests are rarely used as part of routine clinical practice and therefore, a basic understanding of these tests may be lacking. Although aspirin resistance can be categorized as clinical or laboratory resistance, determining laboratory resistance is the only way to determine resistance before treatment failure occurs. Therefore, knowledge of platelet assays to determine aspirin resistance is of importance. The following review aims to provide a framework for clinicians to understand the main principles of platelet function tests. This includes comparison of the most frequently used platelet assays to diagnose aspirin resistance, including the basic mechanism, methodology, reference ranges, inter-assay comparison, and their respective clinical considerations when using.

Evaluation of weight based enoxaparin dosing on anti-Xa concentrations in patients with obesity.

Current treatment dose of enoxaparin is based on total body weight (TBW), however dosage in obesity remains unclear. "Dose capping" commonly occurs if TBW > 100 kg minimising bleeding risk. However, this may result in under-dosing and increasing embolisation risk. The primary objective evaluated efficacy of current dosing strategies in obese patients and determined if resultant anti-Xa concentrations (aXaC) were therapeutic. The secondary objective was to investigate if an uncapped 0.75-0.85 mg/kg (TBW) twice daily dose, advocated by previous authors, results in therapeutic aXaC (0.5-1.0 IU/ml). This retrospective study included 133 patients with a median TBW of 128 kg, producing 59% therapeutic, 15% sub-therapeutic and 26% supra-therapeutic aXaC. Approximately 60% of patients in each dose group (< 0.75, 0.75-0.85 and > 0.85 mg/kg) had a therapeutic aXaC, however the percentage of sub-therapeutic versus supra-therapeutic was higher in the < 0.75 (27% vs 9%) and > 0.85 mg/kg (10% vs 34%) groups respectively. Most patients who weighed 100-119 kg (TBW) received doses > 0.85 mg/kg, however 32% had toxic aXaC. Those between 120 and 139 kg (TBW) had a high percentage of therapeutic aXaC (87%) when dosed < 0.75 mg/kg and a high percentage of supra-therapeutic aXaC (71%) when dosed > 0.85 mg/kg; although numbers were low. Dose reduction occurred in patients > 140 kg (TBW), however < 0.75 mg/kg resulted in higher percentage of sub-therapeutic aXaC (42%). Dosing at 0.75-0.85 mg/kg results in 62% of therapeutic, 14% sub-therapeutic and 24% supra-therapeutic aXaC. This appears to be a "safe" starting dose-range, however all obese patients should have aXaC monitoring due to high inter-patient variability.

A Narrative Review of Aspirin Resistance in VTE Prophylaxis for Orthopaedic Surgery.

Total hip arthroplasties (THA) and total knee arthroplasties (TKA) confer one of the highest risks for developing venous thromboembolism (VTE) and pharmacological prophylaxis is imperative to help mitigate the risks. Aspirin is the most cost-effective medication for VTE prophylaxis, and its use post-THA/TKA has grown in popularity. Aspirin resistance is categorised as clinical or laboratory resistance with obesity, advancing age, diabetes mellitus, dyslipidaemia and inflammatory diseases identified as risk factors for aspirin resistance. Treatment failure due to aspirin resistance has been reported in cardiovascular and cerebrovascular disease leading to increased rates of mortality and re-embolisation. However, aspirin resistance in patients undergoing a THA/TKA has not been described, nor has there been investigation into the incidence rates or clinical outcomes. The aim of this narrative review is to appraise the concept of aspirin resistance in the context of aspirin use for VTE prophylaxis after THA/TKA surgeries. This is important to investigate as the risk factors for aspirin resistance, including obesity, advancing age, diabetes mellitus, dyslipidaemia and inflammatory diseases, are also risk factors for THA/TKA and risk factors for VTE. The presence of aspirin resistance in patients undergoing orthopaedic surgery may place patients at greater risk of thrombotic events if aspirin is prescribed for VTE prophylaxis. This could further increase the risk of complications associated with VTE and potential long-term consequences such as post-thrombotic syndrome. Future research is required to explore and quantify the rates of aspirin resistance and the clinical outcomes in orthopaedic patients; especially in those patients with these overlapping risk factors for THA/TKA, VTE and aspirin resistance.

Paliperidone Long-Acting Injections in Huntington's Disease for Motor and Behavioural Disturbances.

Oral antipsychotics are used to treat motor and behavioural disturbances in Huntington's disease (HD). However, patients with behavioural disturbances are often non-compliant, thus the oral route is inappropriate. The effects of antipsychotic long-acting injections (LAI) in HD are significantly underrepresented in literature. Paliperidone LAI (P-LAI), an atypical antipsychotic, has benefits over other antipsychotics LAI with its long dosing interval and no initial oral overlap, but has no documented cases for this indication. This case of a 45-year-old female highlights the use of P-LAI for severe aggression and chorea secondary to HD causing failed placement in assisted-care accommodation and mobility via an electronic-wheelchair. Three weeks after commencing treatment, she could walk unassisted, and displayed no aggression. After 10 months, she still had significant improvements and resided in the same accommodation for 6 months without any concern. Thus, this case suggests that P-LAI may be a treatment option for non-compliant HD patients.