The latest research you need to know
by Kelly Cunningham, MD, Elizabeth Rice, MD, Eduard Vasilevskis, MD, Joshua LaBrin, MD, Kelly Sopko, MD, Shelley Ellis, MD, MPH, Sunil Kripalani, MD, MSc, Section of Hospital Medicine, Vanderbilt University
A guide to this month’s studies
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.
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).
This study is limited by its post-hoc identification and classification of patients using ICD-9-CM codes, which could have resulted in some misclassification. Also, this study includes only two teaching hospitals in an urban setting; the prevalence of hyponatremia might differ in other settings. Causality cannot be determined based on these results.
Bottom line: Hospitalized patients with hyponatremia have increased in-hospital and long-term mortality.
Citation: Waikar SS, Mount DB, Curhan GC. Mortality after hospitalization with mild, moderate, and severe hyponatremia. Am J Med. 2009;122(9):857-865.
Clinical question: Does the addition of clopidogrel to aspirin therapy reduce the risk of major vascular events in patients with atrial fibrillation for whom vitamin K antagonists (VKAs) are unsuitable?
Background: Although VKAs reduce the risk of stroke in atrial fibrillation, many patients are unable to use VKAs and are treated with aspirin instead. The potential benefits of adding clopidogrel to aspirin therapy in this population are unknown.
Study design: Randomized controlled trial.
Setting: Five hundred eighty medical centers in 33 countries.
Synopsis: More than 7,500 patients with atrial fibrillation who were also at high risk for stroke were randomly assigned to receive either clopidogrel or placebo once daily. All patients also received aspirin at a dose of 75 mg to 100 mg daily. A major vascular event occurred in 6.8% of patients per year who received clopidogrel and in 7.6% of patients per year who received placebo (RR 0.89, 95% CI, 0.89-0.98, P=0.01). This reduction primarily was due to a reduction in stroke, which occurred in 2.4% of patients per year who received clopidogrel, compared with 3.3% of patients per year who received placebo (RR 0.72, 95% CI, 0.62-0.83, P<0.001).
Major bleeding occurred in 2% of patients per year who received clopidogrel and in 1.3% of patients per year who received placebo (RR 1.57, 95% CI, 1.29-1.92, P<0.001).
Bottom line: Adding clopidogrel to aspirin in patients with atrial fibrillation who are not eligible for VKAs decreases the risk of major vascular events, including stroke, but increases risk of major hemorrhage compared with aspirin alone.
Citation: ACTIVE Investigators, Connolly SJ, Pogue J, et al. Effect of clopidogrel added to aspirin in patients with atrial fibrillation. N Engl J Med. 2009;360(20):2066-2078.
Clinical question: What are the utilization, yield, and cost effectiveness of tests used for evaluation of syncope in older patients?
Background: Clinicians utilize multiple diagnostic tests to help delineate the cause of syncope, but the yield and cost effectiveness of many of these tests are unclear. Further, it is unknown if considering patient characteristics, as in the San Francisco syncope rule (SFSR), can improve the yield of diagnostic tests.
Study design: Retrospective cohort.
Setting: Single acute-care hospital.
Synopsis: Review of 2,106 admissions in patients 65 and older with syncope revealed that the most common tests were electrocardiogram (99%), telemetry (95%), cardiac enzymes (95%), and head computed tomography (CT) scan (63%). The majority of tests did not affect diagnosis or management.
Postural blood pressure (BP) reading was infrequently recorded (38%) but had the highest yield. BP influenced diagnosis at least 18% of the time and management at least 25% of the time. Tests with the lowest likelihood of affecting diagnosis and management were head CT, carotid ultrasound, electroencephalography (EEG), and cardiac enzymes.
EEG had the highest cost per test affecting the diagnosis or management ($32,973), followed by head CT. The cost per test affecting diagnosis or management for postural BP was $17. Cardiac testing, including telemetry, echocardiogram, and cardiac enzymes, had significantly better yield in patients who met SFSR criteria.
Bottom line: In patients with syncope, the history and exam should guide evaluation, and tests with high yield and low cost per test, such as postural BP, should be prioritized.
Citation: Mendu ML, McAvay G, Lampert R, Stoehr J, Tinetti ME. Yield of diagnostic tests in evaluating syncopal episodes in older patients. Arch Intern Med. 2009;169(14): 1299-1305.
Clinical question: Does early percutaneous coronary intervention (PCI) improve clinical outcomes compared with standard management in patients with ST elevation myocardial infarction (STEMI) who receive fibrinolysis?
Background: Prior research has demonstrated the benefit of timely PCI in the management of acute coronary syndrome, specifically with ST elevation. However, many hospitals do not have this capability and utilize fibrinolysis as a standard alternative. The optimal timing of subsequent invasive intervention following fibrinolysis has not been established.
Study design: Multicenter randomized trial.
Setting: Fifty-two sites in three provinces in Canada.
Synopsis: This study randomized 1,059 patients presenting with STEMI and receiving fibrinolysis to early intervention (immediate transfer to another hospital with PCI less than six hours after fibrinolysis) versus standard intervention (rescue PCI if needed, or delayed angiography at more than 24 hours). The primary outcome was the composite of death, reinfarction, recurrent ischemia, new or worsening congestive heart failure, or cardiogenic shock within 30 days.
The primary outcome occurred in 11% of patients in the early intervention group, compared with 17.2% of patients randomized to standard intervention (RR 0.64, 95% CI, 0.47-0.87, P=0.004). Urgent catheterization was performed within 12 hours of fibrinolysis in 34.9% of patients randomized to the standard treatment group.
This study was not powered to detect differences in mortality and other individual components of the primary endpoint.
Bottom line: STEMI patients who received fibrinolysis had a lower risk of adverse outcomes when receiving transfer and PCI within six hours, compared with standard delayed intervention.
Citation: Cantor WJ, Fitchett D, Borgundvaag B, et al. Routine early angioplasty after fibrinolysis for acute myocardial infarction. N Engl J Med. 2009;360(26):2705-2718.
Clinical question: In patients admitted to short-stay units (SSUs), what characteristics are associated with unsuccessful SSU admission?
Background: Short-stay units have become prevalent in U.S. hospitals, but it is unclear which patient populations are best served by SSUs.
Study design: Prospective cohort.
Setting: Fourteen-bed SSU in a 500-bed public teaching hospital in Chicago.
Synopsis: More than 700 patients admitted to the Cook County Hospital SSU over a four-month period were interviewed and examined, and their ED and inpatient records were reviewed. An SSU admission was defined as “successful” if the length of stay (LOS) was less than 72 hours and the patient was discharged directly from the SSU.
Overall, 79% of patients had a successful SSU admission. In multivariate analysis, the strongest predictors of an unsuccessful SSU stay were subspecialty consultation (OR 8.1, P<0.001), a provisional diagnosis of heart failure (OR 1.9, P=0.02), and limited availability of a diagnostic test (OR 2.5, P<0.001).
The study was limited primarily to patients with cardiovascular diagnoses.
Bottom line: Patients admitted to SSUs who receive specialty consultation, carry a diagnosis of heart failure, or require diagnostic testing that is not readily available might have a longer LOS or eventual inpatient admission.
Citation: Lucas BP, Kumapley R, Mba B, et al. A hospitalist-run short-stay unit: features that predict length-of-stay and eventual admission to traditional inpatient services. J Hosp Med. 2009;4(5):276-284.
Clinical question: Is survival after in-hospital CPR improving over time, and what are the factors associated with survival?
Background: Advances in out-of-hospital CPR have improved outcomes. However, it is unknown whether the survival rate after in-hospital CPR is improving over time, and it is unclear which patient and/or hospital characteristics predict post-CPR survival.
Study design: Retrospective cohort.
Setting: Inpatient Medicare beneficiaries from 1992 to 2005.
Synopsis: The study examined more than 150 million Medicare admissions, 433,985 of which underwent in-hospital CPR. Survival to discharge occurred in 18.3% of CPR events and did not change significantly from 1992 to 2005. The cumulative incidence of in-hospital CPR events was 2.73 per 1,000 admissions; it did not change substantially over time.
The survival rate was lower among black patients (OR 0.76, 95% CI, 0.74-0.79), which is partially explained due to the fact they tended to receive CPR at hospitals with lower post-CPR survival. Gender (specifically male), older age, race (specifically other nonwhite patients), higher burden of chronic illness, and admission from a skilled nursing facility were significantly associated with decreased survival to hospital discharge following CPR.
Limitations of this study included the identification of CPR by ICD-9 codes, which have not been validated for this purpose and could vary among hospitals. Other factors that might explain variations in survival were not available, including severity of acute illness and the presence (or absence) of a shockable rhythm at initial presentation.
Bottom line: Rates of survival to hospital discharge among Medicare beneficiaries receiving in-hospital CPR have remained constant over time, with poorer survival rates among blacks and other nonwhite patients.
Citation: Ehlenbach WJ, Barnato AE, Curtis JR, et al. Epidemiologic study of in-hospital cardiopulmonary resuscitation in the elderly. N Engl J Med. 2009;361(1):22-31.
Clinical question: Is the presence of hospitalist physicians associated with improved performance on standard quality measures for acute myocardial infarction (AMI), congestive heart failure (CHF), and pneumonia?
Background: Previous investigations have demonstrated significant improvements in cost and LOS for patients under the care of hospitalists compared with other inpatient providers. The association between hospitalist prevalence and quality of care, as measured by standard quality process measures, is unknown.
Study design: Cross-sectional.
Setting: More than 3,600 hospitals participating in the Health Quality Alliance (HQA) program.
Synopsis: Investigators looked at a large sample of HQA hospitals in the American Hospital Association survey, and identified facilities with hospitalist services and those without. The primary endpoint was the adherence to composites of standard quality process measures across three disease categories (AMI, CHF, and pneumonia) and two domains of care (disease treatment/diagnosis and counseling/prevention).
Multivariable analyses revealed a statistically significant association between the presence of hospitalists and adherence to composite quality measures for AMI and pneumonia. This association was demonstrated for both treatment and counseling domains.
The study is cross-sectional, so conclusions cannot be drawn about causality. Also, there are likely unmeasured differences between hospitals that utilize hospitalists compared with those that do not, which could further confound the relationship between the presence of hospitalists and adherence to quality measures.
Finally, this study only evaluated hospital-level performance, and it cannot offer insight on the quality of individual patient care by hospitalist providers.
Bottom line: The presence of hospitalists is associated with improvement in adherence to quality measures for both AMI and pneumonia, and across clinical domains of treatment and counseling.
Citation: López L, Hicks LS, Cohen AP, McKean S, Weissman JS. Hospitalists and the quality of care in hospitals. Arch Intern Med. 2009;169(15):1389-1394. TH
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