In This Edition
Literature at a Glance
A guide to this month’s studies
- Risk of VTE with travel
- Hyponatremia and mortality
- Clopidogrel and aspirin for atrial fibrillation
- Cost-effective evaluation of syncope
- Early vs. delayed intervention in STEMI patients receiving fibrinolytics
- Predictors of prolonged SSU length of stay
- Rates of survival for in-hospital CPR
- Hospitalists and hospital quality measures
Travel Increases Risk for Venous Thromboembolism in a Dose-Response Relationship
Clinical question: What is the association between travel and the risk of venous thromboembolism (VTE)?
Background: Previous studies evaluating the relationship between long-distance travel and VTE have been heterogeneous and inconclusive. Though a relationship is often discussed, only about half of prior investigations have identified an elevated VTE risk in those who travel, and the impact of duration on VTE risk is unclear.
Study design: Meta-analysis.
Setting: Western countries.
Synopsis: Studies were included if they investigated the association between travel and VTE for persons using any mode of transportation and if nontraveling persons were included for comparison. Fourteen studies met the criteria, and included 4,055 patients with VTE. Compared with nontravelers, the overall pooled relative risk for VTE in travelers was 2.0 (95% CI, 1.5-2.7).
Significant heterogeneity was present among these 14 studies, specifically with regard to the method used for selecting control participants. Six case-control studies used control patients who had been referred for VTE evaluation. When these studies were excluded, the pooled relative risk for VTE in travelers was 2.8 (95% CI, 2.2-3.7).
A dose-response relationship was identified. There was an 18% higher risk for VTE for each two-hour increase in duration of travel among all modes of transportation (P=0.010). When studies evaluating only air travel were analyzed, a 26% higher risk was found for every two-hour increase in air travel (P=0.005).
Bottom line: Travel is associated with a three-fold increase in the risk for VTE, and for each two-hour increase in travel duration, the risk increases approximately 18%.
Citation: Chandra D, Parisini E, Mozaffarian D. Meta-analysis: travel and risk for venous thromboembolism. Ann Intern Med. 2009;151(3):180-190.
Hyponatremia in Hospitalized Patients is Associated with Increased Mortality
Clinical question: Is hyponatremia in hospitalized patients associated with increased mortality?
Background: Hyponatremia is the most common electrolyte abnormality in hospitalized patients. Patients admitted with hyponatremia have increased in-hospital mortality. Long-term mortality in hospitalized patients with hyponatremia is not known. Further, the effects of the degree of hyponatremia on mortality are not known.
Study design: Prospective cohort.
Setting: Two teaching hospitals in Boston.
Synopsis: The study identified 14,290 patients with hyponatremia (serum sodium <135 mEq/L) at admission (14.5%) and an additional 5,093 patients (19,383 total patients, or 19.7% of the 98,411 study patients) with hyponatremia at some point during their hospital stay. After multivariable adjustments and correction for hyperglycemia, patients with hyponatremia had increased mortality in the hospital (OR 1.47, 95% CI, 1.33-1.62), at one year (HR 1.38, 95% CI, 1.32-1.46), and at five years (HR 1.25, 95% CI, 1.21-1.30) compared with normonatremic patients. These mortality differences were seen in patients with mild, moderate, and moderately severe hyponatremia (serum sodium concentrations 130-134, 125-129, and 120-124 mEq/L, respectively), but not in patients with severe hyponatremia (serum sodium <120 mEq/L).