Epidemiology and impact of prophylaxis against venous thromboembolism in trauma patients: analysis of the literature

OBJECTIVE: Unfractionated heparin, low-molecular-weight heparin (LMWH), mec hanical compression, and vena cava filters are part of a large panel of che mical or physical methods proposed to trauma patients as prophylaxis agains t venous thromboembolism. This prophylactic strategy is based on a 1961 aut opsy survey showing a 16.6% rate of pulmonary embolism in this population T he objective of this study was to assess the incidence of deep venous throm bosis (DVT) and pulmonary embolism (PE) in multiple trauma patients. METHODS: A Medline and Current Contents search was conducted for prospectiv e studies including trauma patients with ISS > 9 whose incidence of DVT and PE was evaluated by contrast venography and/or duplex ran and by ventilati on/perfusion lung scan and/or pulmonary angiography and/or autopsy, respect ively. RESULTS: Twelve studies mb the selection criteria for DVT. Among the global population of 2,374 trauma patients (14% of all admissions) 47% suffered l ower limb injury and 17% had severe head injury. Overall incidence of DVT w as about 20%. It was about 38% in patients without prophylaxis (range 2 to 61.5%) and about 13% in patients with prophylaxis (range 0.8 to 37%). Simil ar variations were observed for proximal DVT In comparative studies (unfrac tionated heparin venus LMWH or versus mechanical compression devices) the i ncidence of thromboembolic events varied from 3.2 to 44% in patients given unfractionated heparin, 0.8 to 31% in those given LMWH, and 3.1% to 12% wit h mechanical compression. Thirteen studies met the selection criteria for P E and included an overall population of 4,245 trauma patients where the dia gnosis of PE was suspected only ii the patient had clinical signs. The inci dence of PE and fatal PE was about 1.4% and 0.3% respectively. Only one stu dy systematically studied the presence of PE and showed an incidence of 18. 7% for PE in a population of 32 patients. DISCUSSION: The current literature reports wide variability in methodology, characteristics of the study population and prophylaxis, These differences explain the wide variability from one study to another in the risk factors for venous thrombosis identified by univariate and multivariate analysis. CONCLUSION: Current methodological imperfections make it impossible to corr ectly assess the incidence of DVT and PE in the multiple trauma population. Studies with a rigorous methodology using a precise stratification of the trauma injuries are required to determine the real risk for DVT/PE in traum a patients and to assess the impact of early systematic prophylaxis.