Deep vein thrombosis (DVT) refers to the formation of a clot in one of the deep veins of the legs. A detachment of the thrombus may lead to fatal complications, such as a pulmonary embolism. Normally, blood from the lower limbs is sent back to the heart by muscle contractions and one-way valve systems. A DVT occurs when these mechanisms are defective, leading to stasis of blood flow in the lower limbs.
There are several risk factors for the development of DVT, including increased age, obesity, and malignancy. One of the greatest risk factors for DVT is prolonged surgery and immobilization, which is often seen in the postoperative period following orthopedic surgery. Studies estimate that in the absence of DVT prophylaxis, the incidence of DVT can be as high as 50% to 88% after orthopedic procedures like hip arthroplasty and total knee arthroplasty.1 It is therefore imperative that steps are taken for the prevention of DVT in this group of patients.
The early generation pneumatic compression devices consisted of a single air chamber that when inflated, provided low-pressure compression of the limb. Current devices have multiple air chambers that sequentially inflate in a rapid and graduated manner, therefore improving the hemodynamic response. Sequential compression devices or SCD’s can apply pressure from the calf to the thigh region. SCD's work by squeezing the blood from the limb and displacing it proximally. This aids in increasing the velocity of venous blood flow in the lower limbs, which reduces venous stasis. They also stimulate the release of anti-thrombotic factors, which inhibit activated factor VII, and nitric oxide from the vascular endothelium.
The efficacy of SCD's has been proven by several clinical trials. Urbankova et al. (2005) undertook a meta-analysis analyzing the efficacy of intermittent pneumatic compression devices in preventing DVT.2 They included 15 studies, with a total of 2270 patients. The authors concluded that, in comparison to receiving no prophylaxis at all, the use of these devices was associated with 60% lesser risk of developing DVT.
Another meta-analysis (Ho and Tan, 2014), reviewed 70 trials with a total of 16,164 patients.3 This analysis concluded that intermittent pneumatic compression devices were effective in reducing the incidence of DVT, and combining this with pharmacological prophylaxis was more effective than mechanical devices alone. SCD's have also been found to be superior to graduated compression stockings. A meta-analysis by Morris and Woodcock (2010) showed that compression devices appeared to have a lower rate of DVT incidence when compared to compression stockings.4
Clinical practice guidelines for prevention of DVT in orthopedic surgery patients, such as by the American College of Chest Physicians, 9th edition, and American Academy of Orthopedic Surgeons, have recommended the use of either pneumatic compression devices or anticoagulants such as low molecular weight heparin.5,6 While either method seems effective at providing thromboprophylaxis, there are distinct advantages to using compression devices over anticoagulants. Colwell et al. evaluated 412 patients undergoing hip arthroplasty, who were randomized to receive either low molecular weight heparin, or pneumatic compression devices as prophylaxis.7 They stated that the compression group had significantly lesser major bleeding events as compared to the heparin group, while the rates of DVT were almost comparable. In low-risk patients, it seems preferable to use mechanical compression devices alone. One study by Doran et al. employed risk stratification in 842 patients.8 These patients received either aspirin with pneumatic compression devices, or anticoagulant therapy with heparin and warfarin. They concluded that devices provided comparable DVT prophylaxis to anticoagulants but at a lower cost. These results were supplemented by Odeh et al.,9 who showed that the combination of aspirin and SCD's were as effective as aggressive thromboprophylaxis (using heparin compounds) at preventing DVT in standard risk patients.
With regard to patients who are at higher risk of developing DVT, several studies have shown that augmenting chemoprophylaxis with mechanical forms of prophylaxis, particularly SCD's, is more effective in the prevention of DVT. Edwards et al. prospectively studied 277 patients who underwent total hip arthroplasty.10 Eisele et al. also prospectively studied 1803 patients who were randomized to receive either low molecular weight heparin alone or heparin in combination with SCD's.11 The incidence of DVT was only 0.7% in the group that used SCD's, as compared to 1.7% in the heparin-only group.
One of the main concerns associated with the use of SCD's is compliance. The ACCP guidelines recommend that the device be used for at least 18 hours in a day. Standard SCD's need to be connected to an external power source, and patients may use them only as long as they stay in bed. They are also heavy and cumbersome, so patients tend to feel uncomfortable and end up removing them. It is important that the patient be able to use the devices at home, as thromboembolic events tend to occur after patient discharge. The advent of portable compression devices has reinvigorated interest in this area. These devices are battery-powered, lighter in weight, and can be worn comfortably by the patient even at home. This would help improve the patient’s compliance and therefore result in better clinical outcomes.12 Portable devices do not have power cords or other tubing, so they can be worn safely without fear of tripping or injury. Murakami et al. compared the use of mobile devices with standard ones in trauma patients who received DVT prophylaxis. He noted that compliance was increased by 19% in patients who used portable devices.13
McAsey et al. interviewed 247 patients who used the mobile device for 10 days after total hip arthroplasty. They stated that patients responded positively to the device, and 94.7% of patients said that they would choose this over chemoprophyaxis.14
In conclusion, the efficacy of portable sequential compression devices has been established as being on par with chemoprophylaxis. They may be used alone in low-risk patients, and along with chemoprophylaxis in high-risk patients, who are undergoing orthopedic surgery. Their clear advantage over conventional devices is their ability to improve patient compliance through the convenience of use.Click below to learn more about our DVT solutions for your Ambulatory Surgery Center or Medical Clinic.