Incidence and Prevention of Deep Venous Thrombosis Occurring Late after General Surgery: Randomised Controlled Study of Prolonged Thromboprophylaxis

Objective: To study the incidence of late deep venous thrombosis (DVT), and to evaluate a regimen of prolonged thromboprophylaxis after general surgery.Design: Randomised, controlled, open trial, with blinded evaluation.Setting. University hospital, Denmark.Subjects: 176 consecutive patients undergoing major elective abdominal or non-cardiac thoracic operations, of whom 118 were eligible for evaluation.Interventions: Thromboprophylaxis with a low-molecular-weight heparin, tinzaparin, given for four weeks (n = 58), compared with one week (control group, n = 60).Main outcome measures: Presence of DVT established by bilateral venography four weeks after the operation.Results: The incidence of late DVT in the control group was 6/60 (10%, 95% confidence interval (CI) 4% to 21%). In the prophylaxis group it was 3/58 (5.2%, 95% CI 1% to 14%) (p = 0.49).Conclusion: Prolonged thromboprophylaxis had no significant effect on the incidence of DVT occurring late after general surgery.