Guideline Development Group

Summary of Evidence

Reduced mobility is a known risk factor for VTE, yet the quantity and duration of the reduced mobility that defines degree of risk for VTE is not known.^18-20 Significant variability exists in the literature regarding reduced mobility and the resulting risk for VTE.²¹ Ambulatory patients were found to be at increased risk for developing a VTE with standing time of 6 or more hours (1.9 odds ratio or OR) and/or resting in bed or a chair (5.6 OR).²² Likewise, a significant correlation exists between loss of mobility status for 3 or more days and the presence of LE DVT on Doppler ultrasound.²³

When additional risk factors for VTE are present in an individual who has any reduction in mobility, the risk for VTE is significantly increased. Increased age serves as an example. One study of hospitalized patients older than 65 found reduced mobility to be an independent risk factor for VTE. The risk increased based upon the degree of immobility and relative risk scores were derived according to the degree of immobility (Table 4).^{18, 24} The odds ratio or risk was found to be higher in older patients with more severe limitation of mobility (bed rest versus wheelchair) and when the loss of mobility was more recent (< 15 days versus > 30 days).

Recent national guidelines have associated reduced mobility with increased risk of VTE. ^{19, 25} The National Institute for Health and Clinical Excellence (NICE) guidelines present strong recommendations for the need to regard surgical patients and patients with trauma at an increased risk of VTE. When patients undergo surgery with an anesthesia time of greater than 90 minutes or if the surgical procedure involves the pelvis or lower limb and anesthesia time is greater than 60 minutes, the risk is much greater. Individuals who are admitted acutely for surgical reasons or admitted with inflammatory or intra-abdominal conditions also are at high risk for developing a VTE. These same guidelines emphasized the need to identify all individuals who are expected to have any significant reductions in mobility to be at risk for VTE, and to mobilize them as soon as possible.¹⁹ The American College of Chest Physicians (ACCP) guidelines emphasize prevention of VTE in nonsurgical patients by incorporating non-pharmacological prophylaxis measures including frequent ambulation, calf muscle exercise, and sitting in the aisle and mobilizing the lower extremities when traveling (Grade 2C recommendations).^{25, 26}

Previously, when individuals were diagnosed with a LE DVT, they were placed on bed rest due to the concern that ambulation would cause clot dislodgment and lead to a potentially fatal PE. However, a meta-analysis compiled data from 5 randomized control trials (RCT) on more than 3,000 patients and concluded that early ambulation following diagnosis of a LE DVT was not associated with a higher incidence of a new PE or progression of LE DVT as compared to bed rest.²⁷ Rather, there was a lower incidence of new PE and overall mortality in those patients who engaged in early ambulation. Similar findings, as well as more rapid resolution of pain, were reported in a systematic review which included seven RCTs and two prospective observational studies.²⁸ The importance of mobility is further discussed in key action statement 8.

In summary, mobility should be encouraged in patients while in the hospital and when discharged to prevent the complications associated with immobility. In addition, mobility is recommended for those diagnosed with VTE once therapeutic anticoagulant levels have been reached. (See Action Statement 8)