Epidemiology

VTE, which comprises deep vein thrombosis (DVT) and pulmonary embolism (PE), is a common cause of morbidity and mortality in hospitalized medical patients. The baseline incidence of asymptomatic VTE in hospitalized medical patients without anticoagulant prophylaxis is 7% to 15%. Linked administrative database studies indicate that 1.7% of hospitalized medical patients develop symptomatic VTE within 3 months of hospitalization. This is lower than in surgical patients, who have a risk of 2% to 3%. However, because of the sheer number of hospitalized medical patients when compared to surgical patients, the burden of illness is high. Approximately 50% to 70% of symptomatic VTE and 70% to 80% of fatal PE occur in medical patients, and recent hospitalization for medical illness accounts for 25% of all VTE diagnosed in the community. The quoted risk of 1.7% is also based on the risk in all medical patients, some of whom have a lesser illness severity. In prospective studies assessing medical patients who have at least one major risk factor for VTE such as severe cardiac or respiratory disease and do not receive VTE prophylaxis, the incidence of DVT as detected by venography is approximately 10% to 15%. In the absence of anticoagulant prophylaxis, the incidence of proximal DVT, which is the type of DVT most likely to embolize, is approximately 5% and the incidence of PE is 0.5%. VTE is associated with potentially serious long-term complications, including post-thrombotic syndrome, cardiorespiratory insufficiency, recurrent VTE, and bleeding associated with anticoagulant therapy. VTE is also a common cause of readmission to the hospital, and is associated with increased hospital costs and length of stay.

Pathophysiology

Hospitalization for an acute medical illness is independently associated with about an 8-fold increased risk for VTE. Chart audits have shown that nearly all hospitalized medical patients have at least one VTE risk factor, be it immobility, increased age, cancer (active or occult), or acute medical illness (eg, congestive heart failure, obstructive lung disease). Certain populations of hospitalized medical patients, such as those in the intensive care unit, have additional risk factors including central venous catheterization. (Table 60-1)

Does This General Medical Patient Need VTE Prophylaxis?

There is no standardized or validated risk stratification algorithm to guide VTE prophylaxis in medical patients. As a general guide, medical patients presenting with ischemic stroke, chronic heart failure, chronic obstructive pulmonary disease, cancer, history of prior VTE, sepsis, acute neurologic disease, or severe inflammatory disease should be given VTE prophylaxis. Immobility is considered a weaker risk factor, and is difficult to clearly define. However, patients who cannot ambulate without assistance still merit consideration for prophylaxis.

A recent meta-analysis has shown that pharmacologic prophylaxis is effective in reducing fatal PE, symptomatic PE, and symptomatic DVT by more than 50% with no increase in major bleeding compared with placebo in general medical patients. There is no effect on all-cause mortality, and the number needed to treat to prevent one symptomatic PE is high (more than 300). However, due to the large number of at-risk hospitalized medical patients, thromboprophylaxis still provides an opportunity to reduce morbidity in a significant number of patients. There does not appear to be a difference in bleeding rates of VTE rates between with low dose unfractionated heparin (LDUH), low molecular weight heparin (LMWH), and fondaparinux. Of note, fondaparinux and tinzaparin, though frequently used for VTE prophylaxis in medical patients, have not yet been approved for use in this population.

In patients with an increased risk for bleeding (Table 60-2), physicians commonly choose mechanical methods of thromboprophylaxis to increase venous flow and reduce stasis: graduated compression stockings (GCS), intermittent pneumatic compression devices (IPC), and the venous foot pump.