Is there still an avoidable fraction of post-operative thromboembolic complications with heparin prophylaxis? The results of a case-control surveillance. Collaborative Group on Heparin Prophylaxis in Surgery (S.E.P.E.C.).

A case-control multicenter study was set up in 68 general and specialistic wards in Italian regional hospitals in order to assess whether underuse of heparin prophylaxis may account for at least a fraction of the thromboembolic events still occurring in surgical patients. 100 cases with clinically relevant thromboembolic or hemorrhagic events occurring during hospitalization for major surgery and 200 controls were identified. Controls were selected among patients not presenting any of the events under study during the same period of observation and were matched with cases for age, sex, and type of surgery. The results of the study suggest that heparin use in routine conditions of care closely reflects the "consensus" knowledge, patients at higher risk (specifically orthopedic surgical patients, those with varicose veins or with preoperative bed rest longer than 3 days) being treated more frequently with heparin. Absence of heparin prophylaxis does not appear to represent a specific risk factor for the occurrence of index events (OR 0.73, 95% CI = 0.42-1.26). Despite the higher rates of heparin exposure, the presence of varicose veins is associated with a statistically significant increase in the risk of postoperative complications (OR 2.23, 95% CI = 1.07-4.65). This study indicates that among known pre- and peri-operative risk factors only varicose veins may be unprotected by the current prophylaxis practice.