Predicting failure of low-dose prophylactic heparin in general surgical procedures

Despite prophylaxis with low-dose heparin (LDH), postoperative thromboembolism (TE) still occurs in 10 per cent of patients undergoing abdominal operations. To identify predictors of TE in spite of LDH, 171 patients undergoing abdominal operations and receiving LDH were screened with the fibrinogen uptake test. Diagnosis of TE was confirmed in 24 (14 per cent; 95 per cent confidence limits of 9 to 20 per cent) by either venography or pulmonary scintigraphy, or both, or autopsy. As analyzed by multiple logistic regression, only age, body mass index, preoperative hemoglobin concentration and colorectal operations (yes or no) contributed to the prediction of failure of LDH, whereas sex, malignant lesion, previous TE, hypertension, diabetes mellitus and varicose veins did not. Based on the first 81 patients, an index was constructed that was able to identify 11 of 13 patients with TE and exclude 34 of 68 without TE. This index was then applied on a second series of 90 patients in whom it correctly identified ten of 11 patients with TE and excluded 40 of 79 patients without TE. It is concluded that, with the use of the index, it is possible to identify a group of patients undergoing elective abdominal operations in whom LDH is not sufficient prophylaxis. A practical approach to bedside prediction of failure of LDH prophylaxis by use of a simple score table is suggested.