Venous thromboembolism (VTE) remains a serious clinical issue with an unacceptable rate of mortality and associated morbidity that includes pulmonary embolism and deep vein thrombosis (DVT). 1 However, the incidence of these events has been decreasing steadily during the last decades, thanks to chemical and mechanical prophylaxis, fast-track procedures and related improvements in the rehabilitation processes, and major progresses in surgical and anaesthetic techniques. At the present time, for

more »

... nstance, less than 1% of patients undergoing major orthopaedic surgery will develop a symptomatic VTE. The rate of postoperative pulmonary embolism is now below 0.5% and the fatal pulmonary embolism rate is much lower than 0.1%, even after major surgery. 2 A recent retrospective cohort of 1 432 855 patients undergoing surgery under general anaesthesia at 315 American hospitals from 2005 to 2011 found an overall VTE rate of 0.96% with low rates for DVT (0.71%) and pulmonary embolism (0.33%). 3 Of note, as compared with a procedure of average duration, patients undergoing the shortest procedures experienced a 0.86 [95% confidence interval (CI) 0.83 to 0.88] decrease in the odds of developing VTE. Figures are even more impressive for day-case procedures. Several explanations may account for this. Procedures are generally shorter and have an intrinsic lower risk and the patient population may be more selective. For example, the day-case operative cohort may include a greater proportion of younger people, who are more mobile and tend to be discharged back home on the same day as surgery, thereby minimising the time of strict immobility. In these patients, the magnitude and duration of risk of VTE associated with different surgical procedures is still largely unknown. With regard to the level of risk, several cohort studies have evidenced a very low level of risk, although it should be noted that only predominately minor procedures were included. As an example, the total global risk for VTE within 60 postoperative days only reached 0.04% in the Engbaek study in 2006 (16 048 patients including 18 736 day surgery operations). 4 With such low figures, one could wonder whether VTE prophylaxis should even be considered for such procedures. The whole picture, however, appears to be a little bit more complicated. A prospective, observational, cohort study using the American College of Surgeons National Surgical Quality Improvement Program database from 2005 to 2009 included 259 231 adult patients who had outpatient surgery or surgery with subsequent 23h observation. 5 The main outcome measure was the 30-day incidence of VTE requiring treatment, which for the overall cohort was less than 0.15%. This study has identified several independent risk factors for VTE: current pregnancy [adjusted odds ratio (OR) 7.80]; active cancer (OR 3.66); age 41 to 59 years (OR 1.72); age at least 60 years (OR 2.48); BMI at least 40 kg m À2 (OR 1.81); operative time at least 120 min (OR 1.69); arthroscopic surgery (OR 5.16); saphenofemoral junction surgery (OR 13.20); and venous surgery not involving the great saphenous vein (OR 15.61). The Million Women Study also provides very interesting data. In-patients undergoing surgery have a seven times greater VTE risk than out-patients; however, even for day-case surgery, the VTE risk persists for up to 12 weeks after the procedure. 6