Trauma is the leading cause of death in Americans up to 44years old with; more than 180 000 people lose their lives to trauma, and it costs $406 billion a year, including both health care costs and lost productivity.1 Worldwide, 5.8 million people die because of trauma every year.2 One significant condition occurring in trauma patients is the deep vein thrombosis (DVT). Deep vein thrombosis refers to development of thrombosis resulting from platelet adherence to the vein wall as the thrombosis becomes larger, which could obstruct the vein.3
The incidence of DVT varies from 5% to 63% in trauma patients, depending on a patient’s risk factors, modality of prophylaxis, and methods of detection.4,5 Risk factors for DVT in trauma patients include aging, prolonged immobility, lower-extremity and pelvic fractures, spinal cord injuries, head injuries, and ventilator days of more than 3.6-10 Recognized risk factors for DVT are related to Virchow’s triad (stasis, vessel injury, and hypercoagulability); trauma patients often have these factors.11 Prolonged immobility and being in a static position cause a reduction in venous blood returns and decrease in the supply of oxygen and nutrients to endothelial cells. Use of pharmacological sedations, intubation, catheterization, and neuromuscular block may decrease the velocity of limb venous blood flow.12-17
In addition, direct injury to blood vessels can cause intimal damage leading to the exposition of tissue factor at the sites of injury. This may cause extensive activation of the coagulation cascade with consumption of clotting factors and platelets. If so, the result is that clotting factors and platelets are depleted because of the body’s attempts to form multiple clots.18 It is well known that critically injured patients experience early coagulopathy due to traumatic bleeding then go into a hypercoagulable state because of the systemic inflammatory response and increase in C-reactive proteins in the blood.19 After trauma, thromboplastin (tissue factor) and markers of thrombin generation increase, and the levels of natural anticoagulants such as antithrombin, protein C, and protein S are reduced.20,21 Besides the consumption of clotting factors, acidosis, and hypothermia leading to reduced activity, dilution from intravenous fluids and packed cell administration are also accepted causes of traumatic coagulopathy.22,23
Deep vein thrombosis prophylaxis is essential in the management of trauma patients. Mechanical thromboprophylaxis is commonly used in trauma because of its ease of use and low risk of bleeding.24 Mechanical devices such as graduated compression stockings (GCSs) and intermittent pneumatic compression (IPC) stockings are used in trauma patients when chemical prophylaxis is contraindicated (eg, active or recent bleeding, severe thrombocytopenia) or as adjunct to chemical prophylaxis. These devices work by sequential inflating and deflating, to give an intermittent gradient of pressure to propel the flow of blood, prevent stasis, and activate the fibrinolytic pathway.25
Mechanical thromboprophylaxis could be effective in reducing DVT in trauma patients. However, trauma patients cannot use these devices if they have a recent lower-extremity surgery, fractures, or soft tissue trauma.26 A previous Cochrane review focusing on high-risk patients showed that combined methods (pharmacological and mechanical interventions) decreased the incidence of DVT.27 Nevertheless, this systematic review did not examine the effects in the subgroup of trauma patients. Also, a previous systematic review by Velmahos et al28 did not find evidence of effectiveness for either pharmacological or mechanical interventions.
Guidelines related to IPC, GCSs, and A-V foot pumps as methods of thromboprophylaxis in trauma patients varied a lot and are unclear. The American College of Chest Physicians (ACCP)29 recommended IPC and GCSs to be used in major trauma patients, but foot pump was not included in their recommendations. Meanwhile, the Eastern Association for the Surgery of Trauma7 guidelines did not mention GCSs, highlighting that “A-V foot pumps may be used as a substitute for IPC in high risk trauma patients who can not wear IPC.” In addition, there is no comprehensive and updated systematic review since the one published by Velmahos et al28 from 15 years ago. Also, there is no guideline offering a hierarchy of efficacy and optimal use of mechanical thromboprophylaxis in trauma patients. Therefore, it is necessary to conduct a systematic review to review the literature on the effect of sequential compression devices (SCDs) in preventing DVT among trauma patients. The purpose of this systematic review is to review the literature on the effect of compression devices in preventing DVT among trauma patients.
Data Sources and Searches
We searched 3 databases: PubMed, Cochrane Library, and CINAHL from 1990 to 2014. We searched the references of included studies and systematic reviews for additional potential studies. The search included the following keywords: “prevention,” “DVT,” “sequential compression devices,” “trauma patients.” The search was done from March to June 2014. The search process is shown in the Figure 1.
Relevant articles written in English were reviewed in full length to make sure that they met the inclusion criteria, including (1) randomized controlled trials (RCTs), (2) adult people 18 years or older, (3) trauma patients with blunt or penetrating trauma, and (4) trauma patients who received mechanical thromboprophylaxis using SCDs or IPC and foot pump. Studies were excluded if target population were children and nontrauma and if the trial recruited acute spinal injuries. The primary outcome was the incidence of DVT. A total of 5 RCTs were found to meet the study criteria.
Quality Assessment of the Studies
The authors assessed the risk of bias for each trial using the risk of bias assessment tool from the Cochrane Handbook.30 To complete the table of risk of bias, we compared each trial’s performance against the following domains: sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting, and “other bias.” Our judgment of the risk of bias was reported as “low risk,” “high risk,” or “unclear risk.” The results of the risk of bias assessment are displayed in Table 1.
We identified 5 RCTs that tested the effect of SCDs on DVT outcomes in trauma patients. These studies were conducted between 1990 and 2014 with sample from 2 countries, including the United States (4 trials) and Canada (1 trial). A total of 1072 patients were involved in 5 trials. Two trials by Dennis et al31 and Fisher et al32 studied the effects of SCDs in preventing DVT in orthopedic trauma patients and severely injured patients versus no thromboprophylaxis. Three trials by Anglen et al,33 Elliott et al,34 and Stannard et al35 studied the effect of the thigh-calf SCDs versus the plantar venous IPC devices (foot-calf pump).
Effect of Sequential Compression Devices Versus No Thromboprophylaxis
Dennis et al31 studied the efficacy of deep venous thrombosis prophylaxis in trauma patients. The authors found that there were 18 cases of lower-extremity DVTs for a total of 4.6% of the total population. The incidence of DVT was 2.9% of prophylaxis group and 8.8% without prophylaxis (P < 0.02 by χ2 test). They concluded that DVT prophylaxis can significantly reduce the incidence of DVT in trauma patients with injury severity score of greater than 9.
Fisher et al32 investigated the effectiveness of pneumatic sequential leg compression devices for the prevention of thromboembolic disease in orthopedic trauma patients with hip and pelvic fractures. The incidence of a venous thromboembolic event in the control group was 11.3%, and in the experimental group, 4%. This difference was statistically significant (P = .02). In the control group, 9 patients had proximal venous thrombus, and 3 patients had both DVT and PE. In the experimental group, 4 patients had both proximal vein thrombosis and PE. These patients were also stratified into hip and pelvic fracture groups. In the hip fracture patients, the control group had a thromboembolic event incidence of 12%, and the experimental group, 4% (P = .03). In the pelvic fracture group, there was a thromboembolic incidence of 11% in the control subjects, as did 6% of the experimental group (P = .67). This trial demonstrated that pneumatic sequential leg compression devices are effective in reducing the incidence of thromboembolic events after hip trauma.
Effect of Thigh-Calf Sequential Compression Device Versus Venous Intermittent Pneumatic Compression Devices (Foot-Calf Pump)
Anglen et al33 investigated the effect of plantar compression compared with leg compression for prevention of deep venous thrombosis in orthopedic trauma patients. The results revealed that 3 patients developed DVT in the planter compression group, whereas no patient developed DVT in the leg compression group. Although the numbers were too small to give statistically meaningful results, there is no significant difference in the thrombosis rate (4% of plantar compression vs 0% of leg compression).
Elliott et al34 compared the effectiveness of the calf-thigh sequential pneumatic compression device with the plantar venous IPC device in the prevention of venous thrombosis after major trauma. Twenty-one percent of patients who were randomized to plantar venous IPC and 6.5% of patients who were randomized to calf-thigh sequential pneumatic compression had DVT detected by compression duplex ultrasonography (P = .009). Seven of 13 patients had bilateral DVT after prophylaxis with plantar venous IPC, whereas all 4 patients had unilateral DVT after prophylaxis with calf-thigh sequential pneumatic compression. The incidence of proximal DVTs was 1.6% in the calf-thigh sequential pneumatic compression group, whereas it was 4.8% in the plantar venous IPC group.
Stannard et al35 evaluated sequential and pulsatile mechanical prophylaxis against DVT on pelvic and acetabular fractures after trauma. Deep vein thrombosis developed in 19% of patients in the thigh-calf low-pressure sequential-compression device group, with 13% having a large or occlusive clot and 2% having a documented pulmonary embolism. In calf-foot high-pressure pulsatile-compression pump group, DVT developed in 9% of patients, with 4% having a large or occlusive clot and none having a documented pulmonary embolism. The overall incidence of DVT in the study was 14% of the total population (P = .265), although there was a trend toward larger or occlusive clots in the thigh-calf low-pressure sequential-compression device group than in the calf-foot high-pressure pulsatile-compression pump group (P = .16). Increased patient age and the time elapsed from injury to surgery were found to be associated with higher rates of thrombosis. The results are displayed in Table 2.
The purpose of this systemic review was to review the literature on the effect of SCDs in preventing DVT among trauma patients. Five RCTs that presented the effect of compression devices in trauma patients on incidence of DVT were reviewed. The results were supported by the most recent guidelines from the ACCP published in 2012. For major trauma patients, if there is low-molecular-weight heparin (LMWH) and low-dose unfractionated heparin contraindication, mechanical prophylaxis with IPC is recommended over no prophylaxis when not contraindicated by lower-extremity injury (ACCP).29
Dennis and colleagues’31 RCT tested the SCDs for prophylaxis against DVT, and the findings showed a reduction in DVT compared with control subjects with no prophylaxis. Whereas Fisher et al32 reported a significant reduction in DVT in patients with hip fracture compared with control subjects with no prophylaxis. These results, congruent with those of Velmahos et al,36 reported that the incidence of DVT was the same rate among injured patients who had a prophylaxis with SCDs or a combination of low-dose heparin and SCDs. Also, Ginzburg et al,37 in a large, prospective, randomized trial, compared IPC with LMWH in trauma patients; the IPC was equivalent to the LMWH in terms of DVT prophylaxis, but this study concluded that mechanical devices are safe and should be considered when anticoagulant DVT prophylaxis is contraindicated.
Anglen et al,33 in a prospective, randomized, controlled study of 124 high-risk orthopedic patients (pelvic, acetabular, or femur fracture), reported that DVT incidence was 0% in the SCD group and 4% in the A-V foot-pump group. However, 1 patient in the (A-V) foot-pump group had a nonfatal PE. Overall, the incidence of DVT was lower than those in other studies in similar high-risk population. While Elliott et al34 concluded that the calf-thigh sequential pneumatic compression prevents DVT more than does plantar venous IPC after major trauma without lower-extremity fracture, the incidence of DVT was 6.5% in the calf-thigh sequential pneumatic compression group and 21% in the plantar venous IPC group. These results are not congruent with those of Spain et al38 in a nonrandomized study of 184 high-risk patients, who divided patients into SCD prophylaxis or A-V foot pumps in patients with lower-extremity fractures. The incidence of DVT was similar between groups.
Stannard et al35 reported that a reduction in the incidence of DVT among patients with pelvic and acetabular fracture after trauma was higher in a thigh-calf sequential-compression device group than that in calf-foot high-pressure pulsatile-compression pump group; the authors concluded that pulsatile compression was associated with fewer DVT than standard compression. In a recent study of Stannard et al,39 enoxaparin treatment was compared with enoxaparin plus foot pump treatment. The prevalence of DVT was 13.4% in the enoxaparin group and 8.7% in the enoxaparin-plus-foot-pump group. Early mechanical prophylaxis with foot pumps and the addition of enoxaparin on a delayed basis were a very successful strategy for prophylaxis against venous thromboembolic disease following serious musculoskeletal injury.
LIMITATIONS OF THE STUDY
This review had a number of limitations that impacted the generalization of its findings. One major limitation of this review is a small number of trials, a small sample size that made these samples less representative of the population and led to decreased power to show the observed rate difference that was statistically significant.33,34,35 There was also a lack of optimal design methods used in 1 trial, including randomization and control,31 where 37% of patients in the control group were switched from no prophylaxis to an SCD at the discretion of the attending surgeon; this may be due to perceived high risk for DVT. In the study of Anglen et al,33 the population is quite heterogeneous. Also, there were no uniform screening methods to confirm DVT diagnosis with use of duplex ultrasound in the studies of Anglen et al,33 Elliott et al,34 and Stannard et al35, whereas Dennis et al31 used Doppler ultrasonography and Fisher et al32 used both Doppler and duplex ultrasonography. Regarding patient compliance, Fisher et al32 and Stannard et al35 reported that compression devices were well tolerated by patients and nurses.
IMPLICATIONS FOR PRACTICE AND RESEARCH
Mechanical prophylaxis methods are necessary and effective in reducing the incidence of DVT among trauma patients. Although pneumatic compression and other mechanical methods for DVT prevention may be beneficial, this approach has limitations, including need to ensure patient compliance, lack of standards for devices and intensity of compression, and need to clean and maintain the devices, particularly compression pumps that would be reused by many patients. There is also a little evidence from RCTs supporting their safety or efficacy either in this subset of patients or in critically ill patients in general, but it is recommended to be used where there is a contraindication to LMWHs. We recommend future RCTs with large samples to investigate the efficacy and optimal use of mechanical prophylaxis in trauma patients.
We found evidence that SCDs reduce the incidence of DVT in trauma patients, SCDs were more effective than no prophylaxis, and foot pumps were more effective than SCDs. Based on this review, there is no strong evidence to guide the optimal use and proper techniques of mechanical thromboprophylaxis applications in clinical practice. So, there is a need to develop evidence-based standards and guidelines based on best evidence available for mechanical thromboprophylaxis applications and safe use, implement educational programs for health care providers to improve their performance, enhance patients’ outcome, and achieve the effectiveness of mechanical prophylaxis devices.
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