Disorders of the peripheral venous system are prevalent and a significant cause of disability and potential death in the Western world. The frequency of venous disorders of the lower extremities is unique to humans and is reflective of the consequences of our upright posture and gravity. Deep vein thrombosis (DVT) is a common disorder frequently seen in both the inpatient and outpatient settings, which increases the risk of pulmonary embolism (PE), a potentially fatal complication. Pulmonary embolism is an important healthcare disorder because of not only its association with significant morbidity and mortality but also its significant cost factor to the US healthcare economy. Venous thromboembolism (VTE), which includes both DVT and PE, is an important and frequent sequela of these 2 conditions and is a major and often unrecognized cause of morbidity and mortality in hospitalized patients.1-3
Incidence of VTE
In the United States, the annual incidence rate of "first-time" VTE is approximately 100 per 100,000 person-years, with as many as 300,000 new cases annually.4,5 In a meta-analysis by Fowkes et al,6 it was found that the rate of new DVT cases ranges from 4.6 to 9.6 per 10,000 person-years, with a weighted mean incidence of first DVT in the general population studied of 5.04 per 10,000 person-years. They also determined the incidence increases with age: 2 to 3 per 10,000 person-years at 30 to 49 years of age to 20 per 10,000 person-years for those 70 to 79 years old (Table 1).6 Despite the use of oral contraceptives and hormone replacement therapy in women, the incidence is approximately the same for both men and women.6,7
Six percent of DVT cases and 12% of PE cases lead to death. Most of the relevant data affecting reported incidences of VTE rely on data from autopsy, which generally report a higher prevalence of cases with PE than DVT. In addition, there appears to be variability of prevalence regarding ethnicity, with a significantly higher proportion of whites and African Americans than among Hispanic groups.7 Other variables include sex, age, seasonal variation, recurrent VTE, and relative incidence of PE versus DVT. Mortality from VTE is strongly correlated with cancer, age, and cardiovascular disease.7
VTE as a Chronic Illness
For those experiencing a first episode of VTE, their risk for recurrent episodes is elevated: 21.5% after a first DVT and 27.9% after a second. The risk of recurrence varies with time, with highest risk occurring during the first 6 to 12 months after the incident event.6 Death occurs in 6% of DVT cases within 1 month of diagnosis,4 and the 5-year cumulative event rate for fatal PE after a first DVT is 2.6%.8
In a study involving 355 patients, the incidence of recurrent VTE was 8.6% at 6 months and 17.5% after 2 years. After 8 years, the rate of recurrence was as high as 30.3%. Venous thromboembolism was 8.6% after 6 months and 30.3% after 8 years.9 The risk for having a VTE event never resolves to zero; therefore, VTE should be considered a chronic illness rather than a short-term condition.10
Pathophysiology of VTE
The venous system is composed of 3 parts: a superficial system, a deep system, and intermediate or "communicating" system, which links the superficial with the deep. Valves exist in all 3 systems preventing antegrade flow. The deep vein system handles 80% to 90% of venous return and is composed of paired anterior and posterior tibial and peroneal veins, popliteal veins, and superficial and deep femoral veins. Clinical disorders usually occur as a result of obstruction to the venous return from either thrombosis of the vein lumen or from incompetent valves associated with persistent elevation of venous pressure in the foot or leg.11
Current data suggest that most hospitalized patients have at least 1 risk factor for DVT and that approximately 40% have 3 or more. Identifiable, self-limited events are the cause of about half of DVTs, examples being trauma, stasis, recent surgery, paralysis, or pregnancy. In the other 50%, no identifiable cause is found, and these cases are most often referred to as idiopathic, resulting from numerous and unknown factors.1 Thus, assessment of risk factors for VTE of hospitalized patients should be a key strategy that nurse practitioners use in caring for these patients.
Risk Factors
Identification and documentation of a patient's risk factors for VTE can be the initial step that a healthcare practitioner uses in minimizing and/or preventing this disease. A complete list of risk factors related to VTE can be found in Table 2. Acquired risk factors (as apposed to risk factors involving genetic causes) include smoking, obesity, stasis, hypercoagulability, recent surgery, trauma, and hospitalization. In addition, advancing age, genetic factors, and family history of DVT are also well-established risk factors.1,4,12
Surgery
Surgery-related risk factors include immobilization, infection, dehydration, vessel injury, and duration and type of surgery. Minor surgeries that involve shorter periods and outpatient surgeries have lower incidence of VTE, whereas major surgeries, such as those involving the gastrointestinal system, often because of increased length of hospital stay, involve higher risk. Regarding types of surgeries, obese patients undergoing bariatric surgery are at increased risk for VTE and death caused by PE, and orthopedic surgery patients are at risk when the duration of anesthesia is greater than 3.5 hours.13
Pregnancy
According to data reported by the American Heart Association, young pregnant women and women going through postpartum periods are also at an increased risk.4 But there is a difference in these 2 groups as well. Women in postpartum period are 5 times more likely than pregnant women to develop VTE, and the incidence in these women for developing DVT is 3 times higher than developing PE.4
Women taking oral contraceptives are also at risk. In a study by Dulicek et al,14 DVT occurred in 57% of women mainly because of oral contraception, and in the other 43%, an additional transient eliciting factor was recognized (eg, immobilization of lower limb, minor and major surgery, trauma). The clinical manifestations that were documented included distal thrombosis (58%), followed by proximal DVT (16%), PE (5%), and thrombosis in unusual sites (5%). In 49% of the women, an inherited or acquired thrombophilia was also found, with factor V Leiden mutation in 35% of these individuals.
Travel
Venous thromboembolism is not limited to the hospitalized patients. Various factors increase the risk of VTE in the outpatient setting. Those who remain immobile for prolonged periods, such as sitting on an airplane on long flights or driving/riding in a car for extended periods without interruption, are also at risk for developing this serious condition. Results from the World Health Organization's WRIGHT (WHO Research Into Global Hazards of Travel) project showed that a person's risk for developing VTE after traveling for 4 hours is approximately twice that of someone who travels less.15 Results of this study also showed that those who take multiple flights over a short period are also at a higher risk because of the fact that the risk of VTE does not go away completely after a flight is over but remains elevated for about 4 weeks.15
Risk factors for VTE associated with travel are obesity, being both very tall and very short, and using oral contraceptives.4 The Longitudinal Investigation of Thromboembolism Etiology study evaluated 304 cases of individuals who experienced a VTE: 47% were considered idiopathic, 25% had undergone recent surgery, and 25% had cancer.16
Using Guidelines to Minimize Risk
Almost all hospitalized patients have some risk for developing DVT, and the disorder is often considered hospital acquired. Thus, thromboprophylaxis is supported and encouraged by clinical practice guidelines and performance measures. However, predicting which hospitalized patients are at increased risk and will develop DVT has been shown to be difficult. Screening hospitalized patients is a slow process and has been shown to be without support, because it is either time-consuming and/or lacking specificity. And, because the effectiveness of thromboprophylaxis is both efficacious and specific, most hospitals today support preventive measures and preventive treatments.1
Despite the presence of sufficient evidence to recommend routine thromboprophylaxis for most hospitalized patients, the rate of adherence to recommended guidelines is low.1 Reasons for this low adherence rate include variability in knowledge of risk assessment and appropriate prophylaxis strategies, and a lack of belief and acceptance that the evidence presented in the guidelines for VTE prophylaxis is appropriate in all clinical situations.17 What confuses practitioners is the inconsistency between various guidelines. A good example is the current debate surrounding the guidelines recommended by the American Association of Orthopedic Surgeons (AAOS) and the American College of Chest Physicians (ACCP). The AAOS guidelines conflict with long-established and widely used ACCP guidelines. Both accept that the most important goal of thromboprophylaxis in patients undergoing hip or knee replacement is to prevent PE; however, the ACCP guidelines also include both asymptomatic and symptomatic DVT detected by venography as a measure of the efficacy of thromboprophylaxis. The AAOS rejected DVT as a valid outcome because their advisors considered the link between DVT and PE to be unproven, ignoring randomized data demonstrating that thromboprophylaxis reduces both DVT and PE.18 As a result of this inconsistency, clinical practitioners are left to decide which guideline is more correct for their patients, and patients may be placed at unnecessary risk if the more appropriate guideline is not followed. So, which do you choose?
Conclusion
Venous thromboembolism should be considered a chronic illness rather than a short-term condition. By understanding disease processes and implementing appropriate clinical practice guidelines in the assessment and care of their patients, nurse practitioners can minimize morbidity and mortality associated with this disease.
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