Air Travel and Venous Thromboembolism: A Systematic Review

Abstract

CONTEXT: Despite multiple attempts to document and quantify the danger of venous thromboembolism (VTE) following prolonged travel, there is still uncertainty about the magnitude of risk and what can be done to lower it.OBJECTIVES: To review the methodologic strength of the literature, estimate the risk of travel-related VTE, evaluate the efficacy of preventive treatments, and develop evidence-based recommendations for practice.DATA SOURCES: Studies identified from MEDLINE from 1966 through December 2005, supplemented by a review of the Cochrane Central Registry of Controlled Trials, the Database of Abstracts of Reviews of Effects, and relevant bibliographies. STUDY SELECTION:We included all clinical studies that either reported primary data concerning travel as a risk factor for VTE or tested preventive measures for travel-related VTE. DATA EXTRACTION AND ANALYSIS:Two reviewers reviewed each study independently to assess inclusion criteria, classify research design, and rate methodologic features. The effect of methodologic differences, VTE risk, and travel duration on VTE rate was evaluated using a logistic regression model. DATA SYNTHESIS: Twenty-four published reports, totaling 25 studies, met inclusion criteria (6 casecontrol studies, 10 cohort studies, and 9 randomized controlled trials). Method of screening for VTE [screening ultrasound compared to usual clinical care, odds ratio (OR) 390], outcome measure [all VTE compared to pulmonary embolism (PE) only, OR 21], duration of travel (<6 hours compared to 6-8 hours, OR 0.011), and clinical risk ("higher" risk travelers compared to "lower," OR 3.6) were significantly related to VTE rate. Clinical VTE after prolonged travel is rare [27 PE per million flights diagnosed through usual clinical care, 0.05% symptomatic deep venous thrombosis (DVT) diagnosed through screening ultrasounds], but asymptomatic thrombi of uncertain clinical significance are more common. Graduated compression stockings prevented travel-related VTE (P<0.05 in 4 of 6 studies), aspirin did not, and low-molecular-weight heparin (LMWH) showed a trend toward efficacy in one study.CONCLUSIONS: All travelers, regardless of VTE risk, should avoid dehydration and frequently exercise leg muscles. Travelers on a flight of less than 6 hours and those with no known risk factors for VTE, regardless of the duration of the flight, do not need DVT prophylaxis. Travelers with 1 or more risk factors for VTE should consider graduated compression stockings and/or LMWH for flights longer than 6 hours.

Delirium, A Symptom of UTI in the Elderly: Fact or Fable? A Systematic Review

“…(10) These standards addressed the assembly of study subjects and issues of bias in comparing groups and in the diagnosis of delirium and UTI. In particular, we were looking for study designs that limited "diagnostic suspicion bias" (knowledge of presence of an abnormal urine leading to documentation of delirium) and "exposure suspicion bias" (knowledge of presence of delirium leading to documentation of urine abnormalities).…”

Prevention of VTE in Nonsurgical Patients

“…[128][129][130] The association between air travel and VTE is strongest for fl ights . 8 to 10 h [125][126][127][128][131][132][133] and is increased in the presence of VTE risk factors such as recent surgery. 123 For those on fl ights .…”

“…b There are two reasons for indirectness: estimates of relative risk reduction come from the surrogate, and there is uncertainty regarding the baseline risk. c Estimates for control event rates for venous thrombosis and for pulmonary embolism come from Philbrick et al 131 Defi nition of high risk includes previous episodes of DVT, coagulation disorders, severe obesity, limited mobility due to bone or joint problems, neoplastic disease within the previous 2 years, or large varicose veins. d None of the other trials reported adverse effects, apart from four cases of superfi cial vein thrombosis in varicose veins in the knee region that were compressed by the upper edge of the stocking in one trial.…”

Relation between Air Travel and Venous Thromboembolism

“…The riskt ends to be the same in all modes of travel and only depends on the duration of travel, as well as previous risk factors depending on the individual. Similarly, the risk of developing VTE decreases with increased time after travel, with majority of the air travel related cases occurring in the duration of one to two weeks after the flight (62) . As was previously mentioned, the majority of the travel related VTE occur among passengers with preexisting risk factors.…”