Patterns of Failure of a Standardized Perioperative Venous Thromboembolism Prophylaxis Protocol

Venous thromboembolism (VTE) is a leading contributor to morbidity after operations. We previously implemented a standardized VTE risk assessment, based on the Caprini score, along with risk-stratified prophylaxis. This system reduced the odds ratio of a VTE event from 3.02 to 0.75. We investigated patterns of failure to determine characteristics of patients in whom VTE develops despite the protocol.

We reviewed all nontrauma general surgery patients with evidence of VTE after the inception of a VTE risk assessment and prophylaxis program. Characteristics were recorded, including demographics, diagnoses, operations, risk profile, prophylaxis prescribed, and regimen compliance.

Twenty-seven patients failed the protocol and manifested VTE, representing an overall VTE rate of 0.3%. Of these patients, 63% had emergency operations and 52% underwent multiple operations, compared with 13% and 2.0% of the nontrauma general surgery population in whom VTE did not develop, respectively (p < 0.001). Of patients with VTE, 52% had pre-existing or postoperative infections, 22% had malignancies, but only 15% had missed 1 or more doses of pharmacologic prophylaxis during hospitalization. Five VTEs manifested after discharge; one of those patients was prescribed extended prophylaxis beyond hospitalization, and an extended course was not provided to 3 who were eligible. One patient had underestimation of the Caprini score due to lack of awareness of a family history of VTE.

Emergency and multiple operations seem to confer dramatic hazards for VTE, despite standard prophylaxis. These factors are not currently captured in the Caprini model, but might be significant modifiers of risk that should prompt reassessment, perhaps with a weighted numeric value along with enhanced prophylaxis. It is encouraging that most patients received appropriate prophylaxis in compliance with the protocol.