An Economic Evaluation of Venous Thromboembolism Prophylaxis Strategies in Critically Ill Trauma Patients at Risk of Bleeding

{{Summary
 * title=An Economic Evaluation of Venous Thromboembolism Prophylaxis Strategies in Critically Ill Trauma Patients at Risk of Bleeding
 * authors=T. Carter Chiasson, Braden J.  Manns, Henry Thomas  Stelfox
 * journal=PLoS Med
 * pub_date=2009/06
 * url=http://dx.doi.org/10.1371/journal.pmed.1000098
 * doi=10.1371/journal.pmed.1000098
 * subject=Medicine
 * summary=-

Background
For patients who have been seriously injured in an accident or a violent attack (trauma patients), venous thromboembolism (VTE)—the formation of blood clots that limit the flow of blood through the veins—is a frequent and potentially fatal complication. The commonest form of VTE is deep vein thrombosis (DVT). “Distal” DVTs (clots that form in deep veins below the knee) affect about half of patients with severe trauma; “proximal” DVTs (clots that form above the knee) develop in one in five trauma patients. DVTs cause pain and swelling in the affected leg and can leave patients with a painful condition called post-thrombotic syndrome. Worse still, part of the clot can break off and travel to the lungs where it can cause a life-threatening pulmonary embolism (PE). Distal DVTs rarely embolize but, if untreated, half of patients who present with a proximal DVT will develop a PE, and 2%–3% of them will die as a result.

Why Was This Study Done?
VTE is usually prevented by using heparin, a drug that stops blood clotting, but clinicians treating critically ill trauma patients have a dilemma. Many of these patients are at high risk of serious bleeding complications so cannot be given heparin to prevent VTE. Nonpharmacological ways to prevent VTE include the use of pneumatic compression devices to keep the blood moving in the legs (clots often form in patients confined to bed because of the sluggish blood flow in their legs), repeated screening for blood clots using Doppler ultrasound, and the insertion of a “vena cava filter” into the vein that takes blood from the legs to the heart. This last device catches blood clots before they reach the lungs but increases the risk of DVT. Unfortunately, no-one knows which VTE prevention strategy works best in trauma patients who cannot be given heparin. In this study, therefore, the researchers use decision analysis (the systematic evaluation of the most important factors affecting a decision) to estimate the costs and likely clinical outcomes of these strategies.

What Did the Researchers Do and Find?
The researchers used cost and clinical data from patients admitted to a Canadian trauma center with severe head/neck and/or abdomen/pelvis injuries (patients with a high risk of bleeding complications likely to make heparin therapy dangerous for up to two weeks after the injury) to construct a Markov decision analysis model. They then fed published data on the chances of patients developing DVT or PE, and on the effectiveness of the three VTE prevention strategies, into the model to obtain estimates of the costs and clinical outcomes of the strategies at 12 weeks after the injury and over the patients' lifetime. The estimated incidence of DVT at 12 weeks was 15% for the pneumatic compression device and Doppler ultrasound strategies, but 25% for the vena cava filter strategy. By contrast, the estimated incidence of PE was 2.9% with the pneumatic compression device, 1.5% with Doppler ultrasound, but only 0.3% with the vena cava filter. The expected mortality with all three strategies was similar. Finally, the estimated health care costs per patient at 12 weeks were Can$55,334 and Can$55,831 for the Doppler ultrasound and pneumatic compression device strategies, respectively, but Can$57,377 for the vena cava filter strategy; similar trends were seen for lifetime health care costs.

What Do These Findings Mean?
As with all mathematical models, these findings depend on the data fed into the model and on the assumptions included in it. For example, because data from one Canadian trauma unit were used to construct the model, these findings may not be generalizable. Nevertheless, these findings suggest that, although VTE is common among patients with severe injuries, PE is not a major cause of death among these patients. They also suggest that the use of vena cava filters for VTE prevention in patients who cannot receive heparin should not be routinely used because it is expensive and increases the risk of DVT. Finally, these results suggest that, compared with the other strategies, serial Doppler ultrasound is associated with better clinical outcomes and lower costs.
 * relevance=This paper may change doctors' treatment strategies for blood clots in trauma patients.

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 * journal_volume=6
 * pub_open_access=Yes