Venous thromboembolism (VTE) is a disease that includes both deep vein thrombosis (DVT) and pulmonary embolism (PE). It is a common, lethal disorder that affects both hospitalized and nonhospitalized patients, if overlooked, can lead to long-term complications. VTE results from a combination of hereditary and acquired risk factors.
Vessel wall damage, venous stasis, and increased activation of clotting factors also known as the Virchow triad is the most common cause of VTE mainly DVT. According to the National Institute of Health on the consensus of prevention of pulmonary embolism, all hospitalized patients are to be stratified into low, moderate, high and highest risk levels and treated according to their level of risk. Surgical patients, especially hip and knee patients are classified as highest risk while patients under the age of 40 with minor surgeries lasting less than 30 minutes are considered low risk patients.
The preferred form of prevention of VTE in the low risk group is early active mobilization while a combination of pharmacological and mechanical management is recommended for the highest risk group. In this review, we will focus on the effectiveness of Low Molecular Weight Heparin (LMWH) compared to pneumatic compression devices in the prevention of VTE in very high risk hip and knee surgical patients. PICO Summary: The population included in this review comprised of surgical patients with hip and knee surgery. The intervention examined was the use of LMWH and pneumatic compression devices.
The comparison is LMWH versus pneumatic compression devices and the outcome measured is VTE. Hence the question, in patients undergoing hip and knee surgery, does the use of LMWH, compared to pneumatic compression devices, reduce the rates VTE. Significance: According to the Center for Disease Control, one of the most common causes of death in the hospitalized patient is PE. Although the precise number of people affected by PE and DVT is unknown, an estimated number of 300 000 to 600 000 of PE and DVT cases are reported annually in the United States.
Routine autopsies estimate that 10-25% of hospital deaths are caused by PE, many of which are extensive enough to be the major cause of death in these patients. According to the UMASS Medical School Center for Outcome research, 80% of PE are silent, over 60% of deaths resulting from PE occur within the first 2 hours and 1 in 100 hospitalized patients dies from a PE. Research has also shown that PE remains the most common cause of preventable deaths in hospitalized patients. The UMASS Medical School Center for Outcome Research also reports that over 90% of PE originates from DVT with 50% of PE and over 60% of DVT being preventable.
Hence, the National Institute of Health recommends a more extensive use of prophylaxis treatment in the prevention of DVT and PE especially in high and highest risk patients. However, the major challenges to preventing PE and DVT are effectively predicting which individuals are at risk and ensuring appropriate access to standards of care for these individuals. Evidence Review Search strategy: From the PICO process we conduct a systematic literature review using key terms from our topic. The literature search was conducted through CINAHL, MEDLINE and OVID.
Key terms used for the search were pulmonary embolism, deep vein thrombosis, and post surgical patients. The original search of the PICO question did not relieve sufficient information. The PICO question was revised and key terms were entered into the data bases which revealed more research articles. A combination of these search terms produced a narrower search result consisting mainly of systematic reviews and meta-analysis. Randomized control (primary) studies were then selected from the foot notes and references of some of the systematic reviews and meta-analysis articles.
There was only one article found for the current year (2010) with a large gap of information found from 1978. The information noted from the seventies is still used as current plans of treatment for embolism and thrombosis therapy. Inclusion and exclusion criteria were looked at several times based upon our literature search. We originally look at hospitalized patients that had developed a pulmonary embolism. This criterion was excluded. Next we looked at prevention of venous thrombosis and pulmonary embolism in post surgical patients with emphasis on use of heparin and/or pneumatic compression devices.
The main delimiter use was English language. It was determine that the best and most effective search for our review would be the prevention of deep vein thrombosis and pulmonary embolism in post surgical hip and knee patients. Data Analysis: Table 1 gives a detail overview of the five articles reviewed. Of the five articles reviewed, three of the studies were a direct comparison of the use of LMWH and pneumatic compression devices in the prevention of DVT and PE. The fourth study was on the effectiveness of compression devices and the fifth on the effectiveness of LMWH only.
Amongst the three articles that compared LMWH and the compression device, two of the articles showed that there is a significant difference in the number of DVT between the use of LMWH and compression devices. In the first study of patients treated with total hip arthroplasty, Pitto et al. demonstrated that three out of a hundred patients in the compression group developed DVT and six out of a hundred in LMWH group developed DVT (p < 0. 05).
In like manner, the second study on a group of patients treated with total hip replacement, Santori et al. howed that nine out of sixty seven patients in the compression group developed DVT and twenty three out of sixty five patients developed DVT (p < 0. 05). In the third study on the comparison of LMWH and compression devices, Colwell et al. reported no significant difference (p = 0. 955) in the number of VTE events between groups. In the fourth study by Fordyce et al. , 40% of participants in the control group developed DVT compared to 5% in the intervention group (p < 0. 001). The fifth study, Williams et al. showed no significant difference between heparin and normal saline groups.
Despite the statistical significance of the results, the researchers were unable to draw conclusions on which intervention is most effective based on the sample sizes and lack of control of extraneous variables. Current state of science: Today PE still remains the most preventable cause of death in hospitals, with over 90% of PE originating from DVT. Because of its complex etiology, most PE are undiagnosed and untreated and are only discovered on autopsies. Due to lack of sufficient evidence, the current state of prevention of VTE is per hospital and provider preferences.
These preferences are guided by recommendations from the National Institute of Health consensus on prevention of pulmonary embolisms. Combinations of pharmacological and mechanical method are recommended to prevent pulmonary embolisms with emphasis on early mobilization when possible. Radiology procedures such as duplex ultrasound and venography are used to diagnose DVT while chest x-rays, computed axial tomography scans and blood test (D-dimer) are used to diagnose PE. Patients who eventually develop DVT or PE are either treated with intravenous heparin or placement of inferior vena cava filters.
Rating scale: Our group decided on the John Hopkins Nursing Evidence-based Practice model, Newhouse et al. to rate each study. Using the same model, we graded the overall body of evidence level I for randomized controlled trials and a quality rating scheme of C due to insufficient evidence, inconsistent results and most importantly inadequate sample size. Consistencies and contradictions: All five articles reviewed were randomized control trials comprising of prospective studies some lasting up to six months in hospital settings. The researchers also utilized a multiple post test approach.
Testing for VTE was done at least twice during the course of each study. Due to the design and nature of the study, attrition was a major threat to internal validity and only one study reported a power analysis and effect size. There was also no control of extraneous variables such as the use of aspirin, early mobilization and patient compliance which have major impact on the outcome being measured. This poses threats to internal validity and increases the likelihood of Type I error. Only two out of the five studies were blinded to control for researcher bias.
Although some of the researchers used different methods for measuring the outcome, all the measurements used were scientific procedures which have been tested for accuracy, sensitivity and specificity. This enhances the reliability and validity of the instruments. Small and inadequate sample size was also a major threat amongst all the studies. Small sample sizes significantly increases the standard error of the mean and the chance for a Type II error. With a sample size as small as 84 patients, the researchers were unable to generalize their findings due to lack of external validity.
Translation of Findings Plan for utilization in practice: As a result of unreliable evidence, the findings cannot be generalized to all hospitals. Further research needs to be done and an outcome measurement plan for each hospital put in place to determine the most effective interventions in preventing VTE. This will help identify more gaps in literature and provide an opportunity for change in hospital and physician preferences in regards to VTE prophylaxis. Several studies are in a favor of both mechanical and pharmacological forms of prophylaxis.
As a group, we also think early mobilization, mechanical and pharmacological interventions should be utilized in preventing VTE. When communicating these findings to the audience, we will present to the audience with the significance of the problem, a detail analysis of the literature reviewed and our recommendations for prevention. We will then ask the audience for their suggestions based on the data presented. We will also like to know the audience opinions about the results and if they will change practice based on the evidence provided.
Outcome measurement: A rigorous outcome measurement needs to be implemented to prevent VTE. Given the significance of the problem, stricter measures need to be put in place to accurately identify and prevent VTE. These measures will assess patients understanding of VTE prophylaxis and compliance with treatment. It will also track the knowledge and compliance of healthcare professionals in regards to the significance and prevention of VTE. Patients need to be aware of their levels of risk and healthcare professionals also need to accurately assess and implement preventive interventions based on patient’s degree of risk.
The implementation of an effective outcome measurement plan will generate ideas for future research and subsequently a general standard for VTE prophylaxis. See appendix for levels of thromboembolism risk in surgical patients. Conclusion Change in practice, evidence gaps and future research: Based on the literature review, there is not enough evidence to draw an evidence-based conclusion between the use of LMWH and compression devices. Nonetheless, the Nation Institute of Health recommends that prevention of VTE be based on individual degree of risk.
A combination of both LMWH and compression devices is recommended for patients said to be at highest risk. Because there is currently no standard practice and not enough evidence to conclude from, we are unable to change current practice. More research needs to be done to generate significant evidence. Due to the very sensitive nature and high mortality rates of PE, an outcome measurement plan, listed above, will be ideal. As a group, we believe that, nurses, physicians and the patients lack awareness on the severity and prominence of PE.
Hence our recommendation for future research on VTE prophylaxis is to assess knowledge and compliance levels amongst patients, nurses and physicians. Increased levels of awareness will increase compliance from patients and also enhance proper VTE risk assessment and prophylaxis from nurses and physicians.
