Timing of symptomatic venous thromboembolism after surgery: meta-analysis

Abstract Background The timing at which venous thromboembolism (VTE) occurs after major surgery has major implications for the optimal duration of thromboprophylaxis. The aim of this study was to perform a systematic review and meta-analysis of the timing of postoperative VTE up to 4 weeks after surgery. Methods A systematic search of MEDLINE, Scopus, and CINAHL databases was performed between 1 January 2009 and 1 April 2022. Prospective studies that recruited patients who underwent a surgical procedure and reported at least 20 symptomatic, postoperative VTE events by time were included. Two reviewers independently selected studies according to the eligibility criteria, extracted data, and evaluated risk of bias. Data were analysed with a Poisson regression model, and the GRADE approach was used to rate the certainty of evidence. Results Some 6258 studies were evaluated, of which 22 (11 general, 5 urological, 4 mixed, and 2 orthopaedic postoperative surgical populations; total 1 864 875 patients and 24 927 VTE events) were eligible. Pooled evidence of moderate certainty showed that 47.1 per cent of the VTE events occurred during the first, 26.9 per cent during the second, 15.8 per cent during the third, and 10.1 per cent during the fourth week after surgery. The timing of VTE was consistent between individual studies. Conclusion Although nearly half of symptomatic VTE events in first 4 weeks occur during the first postoperative week, a substantial number of events occur several weeks after surgery. These data will inform clinicians and guideline developers about the duration of postoperative thromboprophylaxis. The timing of venous thromboembolism after surgery was modelled based on a new systematic review and meta-analysis of 22 prospective studies that included thousands of VTE events from various surgical fields. For symptomatic VTEs occurring within 4 weeks after surgery, 47 per cent occurred by the first, 74 per cent by the second, and 90 per cent by the third week after surgery. This model offers evidence of moderate certainty that, although half of symptomatic VTE events occur during the first postoperative week, a substantial number occur up to 3 weeks after surgery. Lay Summary Hundreds of millions of surgical procedures are performed annually worldwide. Blood clots in legs and lungs represent serious, and sometimes fatal, complications of surgery. To prevent these complications, clinicians often give blood thinners to patients. To optimize the st