No decrease in mortality has been demonstrated to result from prophylaxis against venous thromboembolism in general medical patients, although reductions in the incidence of deep venous thrombosis and pulmonary embolism have been noted [26,43,94-98].
The PREVENT study [94,95] had results similar to the MEDENOX study [26] in a similar population of at-risk medical patients, in which low molecular weight heparin (dalteparin) significantly reduced symptomatic pulmonary embolism and asymptomatic deep vein thrombosis compared to placebo. There were no differences in the incidence of sudden death or all cause mortality; major bleeding rates were low and comparable in the two groups.

Meta-analysis of studies comparing the efficacy and safety of low dose heparin versus low molecular weight heparin have not shown a difference in the incidence of venous thromboembolism but have demonstrated an increase in major [98] or minor [96] bleeding with use of low dose heparin [97].

Medical patients are classified as low, moderate, or high risk for venous thromboembolism depending upon their underlying medical condition and other comorbid factors, and should be treated as follows [63]:

Graduated compression stockings should be considered for low risk patients [63,99]
Heparin or warfarin is recommended for patients following myocardial infarction who have no other significant risk factors for venous thromboembolism [63,100]
In acutely ill patients hospitalized with heart failure or severe respiratory disease, or who are confined to bed and have one or more additional risk factors (eg, active cancer, previous VTE, sepsis, acute neurologic disease, inflammatory bowel disease), either low dose heparin or low molecular weight heparin is recommended [26,63,94,101]
All patients should be assessed for their risk of VTE on admission to a critical care unit. Most patients should receive thromboprophylaxis.
For patients with ischemic strokes and lower limb paralysis, low dose heparin or low molecular weight heparin is recommended [63,101,102]
Intermittent pneumatic compression may be used for high risk patients who are at high risk for bleeding, although this recommendation is not based upon clinical trial data [103]
Pregnancy — Subcutaneous low dose heparin is the prophylactic regimen of choice for pregnant patients who are at high risk for deep vein thrombosis and pulmonary embolism, although data on efficacy from controlled trials are lacking [104]. Included among this high-risk group are women with an inherited deficiency of a naturally occurring anticoagulant; despite the absence of clinical data, it has been suggested that such women might benefit from use of anticoagulant prophylaxis during pregnancy and the postpartum period [104]. The benefits of prophylaxis are uncertain in patients undergoing cesarean section, particularly if they have no additional risk factors [104]. (See "Anticoagulation during pregnancy").

Extended travel — Extended travel either by air or on land appears to confer an increased risk of venous thromboembolism. The data supporting this association and possible preventive measures are discussed separately. (See "Overview of the causes of venous thrombosis", section on Extended travel).


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