Incidence and natural history of below-knee deep venous thrombosis in high-risk trauma patients

Background. Venous thromboembolic disease remains a difficult problem in the trauma patient population. The purpose of this study was to delineate the incidence and natural history of below-knee deep venous thrombosis (BKDVT) in high-risk trauma patients. Methods. Patients were stratified into risk categories (low, high, or very high) for deep venous thrombosis on the basis of an institutional practice management guideline and known risk factors. All at-risk patients received either sequential compression devices (SCDs) or subcutaneous heparin (SQH) compounds, and high-risk patients also underwent weekly surveillance by duplex scanning. Very-high-risk patients had prophylactic inferior vena cava (IVC) filter placement. This prospective, observational study examines the duplex results on all high-risk patients. Data regarding method of prophylaxis, the incidence of proximal propagation on serial duplex examinations, and changes in management (anticoagulation or IVC filter placement) were collected on the high-risk patients who developed a BKDVT. Results. Between March 1997 and June 2001, 601 patients were stratified into the high-risk category and underwent a total of 1,109 duplex examinations. Eighty-five patients (14.1%) had 113 BK-DVTs. These patients underwent a total of 212 duplex examinations; all patients developed their BKDVTs within 34 days. Weekly incidence was 40 (47.1%), 25 (29.4%),15 (17.6%),1 (1.2%), and 4 (4.7%) for weeks 1 through 5, respectively. SCDs, SQH compounds, and SCDs with SQH compounds were used on 73, 3, and 9 patients, respectively. In 4 of 85 (4.7%) patients, the BKDVT propagated proximally to an above-knee location in 4 to 8 days. Two of these patients were anticoagulated, and two underwent placement of an IVC filter. One patient (1.2%) with a BKDVT that had not propagated on duplex study developed a pulmonary embolus. Conclusion. Patients identified as high-risk by our practice management guideline had a 14.1% incidence of a BKDVT; 94.1% were diagnosed within the first 3 weeks of hospitalization. Proximal propagation occurred in 4.7% and led to changes in management. Serial duplex examination of the BKDVT alone, rather than systemic anticoagulation or IVC filter placement, appears to be a reasonable treatment alternative.