Background: The reported overall risk of deep venous thrombosis in gynaecological surgery ranges from 7 to 45%. Fatal pulmonary embolism is estimated to occur in nearly 1% of these women. Pharmaceutical interventions are one possible prophylactic measure for preventing emboli in women undergoing major gynaecological surgery. Agents include unfractionated heparin (low -dose and adjusted-dose), low-molecular-weight heparins, heparinoids and warfarin.
Objectives: The objective of this review was to evaluate the effectiveness of warfarin, heparin and aspirin in preventing thromboembolism after major gynaecological surgery.
Search strategy: We searched the Cochrane Menstrual Disorders and Subfertility Group trials register (searched 15 August 2003), the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library issue 2, 2003), MEDLINE (1966 to April 2003), EMBASE (1985 to April 2003), and CINAHL (1982 to April 2003). References from relevant articles were searched and authors contacted where necessary. In addition we contacted experts in the field for unpublished works.
Selection criteria: Randomised controlled trials of heparins, warfarin or aspirin to prevent thromboembolism after major gynaecological surgery were eligible for inclusion.
Data collection and analysis: Thirty-three trials were identified in the initial search. On careful inspection only eight of these met the inclusion criteria. Trials were data extracted and assessed for quality by at least two reviewers. Data were combined for meta-analysis using odds ratios for dichotomous data or weighted mean difference for continuous data. A random effects statistical model was used.
Main results: The meta-analysis of heparin versus placebo found a statistically significant decrease in the number of DVTs in both the all women group (including those with and without malignancy) (OR 0.30, 95% CI 0.12 to 0.76) and the subgroup of only women with malignancy (OR 0.30, 95% CI 0.10 to 0.89). There was no significant difference in the incidence of PE. Oral warfarin reduced DVT when compared to placebo in all women (OR 0.22, 95% CI 0.06 to 0.86) and in women with malignancy (OR 0.18, 95% CI 0.04 to 0.87). Meta-analyses of UH and LMWH showed no statistical difference in any comparison. No studies compared aspirin alone to placebo, heparin or warfarin. There was a statistically significant increase in injection site haematomas associated with heparin compared to placebo (OR 0.30, 95% CI 0.10 to 0.89).
Reviewer's conclusions: Women, undergoing major gynaecological surgery and without contraindications to anticoagulants should be offered thromboprophylaxis. Evidence suggests that UH and LMWH are equally as effective in preventing DVT and the one trial available suggests that warfarin is as effective as UH. There is no evidence as yet to suggest that warfarin, heparin or aspirin reduce incidence of PE.