Venous thromboembolism rates in patients undergoing major hip and knee joint surgery at Waitemata District Health Board: a retrospective audit.

BACKGROUND/AIM: Symptomatic venous thromboembolism (VTE) complicates approximately 4% of major orthopaedic surgical procedures performed without thromboprophylaxis. Randomised clinical trials demonstrate primary thromboprophylaxis reduces VTE rates to <1%, with low rates of clinically important bleeding, using low molecular weight heparin (LMWH), oral FXa inhibitors or thrombin inhibitors. We reviewed the rates of VTE in patients undergoing major hip/knee joint surgery at Waitemata District Health Board (WDHB).

METHODS: Cases of VTE within 90 days of orthopaedic surgery were identified by retrospective audit of data from the haematology VTE database. The number of major hip/knee joint surgeries at WDHB from January 2006 to December 2010 was obtained from clinical coding data.

RESULTS: The cumulative incidence of VTE within 90 days of surgery was 3.29%. The median time from surgery to diagnosis was 7 days. Deep vein thrombosis comprised 75% of cases, 77.6% distal and 23.2% proximal. Pulmonary embolism comprised 26.5% of VTE; 47.7% had right heart strain on computed tomography/echocardiography. Hip fracture surgery comprised one-third of patients. Of patients developing VTE, 85.5% had chemical thromboprophylaxis - aspirin 73%, LMWH 20 mg 16%, LMWH 40 mg 16%, therapeutic LMWH 3%, unfractionated heparin twice daily 1%, and warfarin 4%; 75.6% received mechanical prophylaxis, while 4% of patients received no prophylaxis.

CONCLUSION: VTE incidence after major hip/knee joint surgery at WDHB is high, with pulmonary embolism comprising almost one-third of all VTE in this study, indicating the prophylaxis given is suboptimal. Implementation of appropriate, extended duration prophylaxis as per evidence-based guidelines is required to reduce these rates.