Venous Thrombosis from Air Travel: The LONFLIT3 Study

Abstract

The LONFLIT1 and 2 studies established that in high-risk subjects after long (> 10 hours) flights, the incidence of deep venous thrombosis (DVT) may be between 4% and 6%. The LONFLIT3 study aimed to evaluate methods of prevention in high-risk subjects. Of 467 subjects contacted for the study, 300 were included. These 300 subjects at high risk for DVT were randomized, after informed consent, into three groups: 1) a control group that had no prophylaxis; 2) an aspirin treatment group, in which patients were treated with 400 mg , (tablets of oral, soluble aspirin; one dose daily for 3 days, starting 12 hours before the beginning of the flight); and 3) a low-molecular-weight heparin (LMWH) group, in which one dose of enoxaparine was injected between 2 and 4 hours before the flight. The dose was weight-adjusted (1000 IU [equivalent to 0.1 mL] per 10 kg of body weight). Subjects with potential problems due to prophylaxis with aspirin or LMWH or at risk of drug interactions were excluded. Of the 100 included subjects in each group, a total of 249 subjects completed the study (dropouts due to low compliance or traveling/connections problems were 17%). Age and sex distribution were comparable in the three groups as well as risk distributions. Mean age was 47 (range, 28-75; SD, 11; 65% males). Of the 82 subjects in the control group, there were 4.82% of subjects with DVT with two superficial thromboses. In total 4.8% of limbs suffered a thrombotic event. Of 84 subjects in the aspirin treatment group, there were 3.6% of patients with DVT and three superficial thrombosis. In total 3.6% of limbs had a throm botic event. In the LMWH group (82 subjects), there were no cases of DVT. One superficial thrombosis was documented. In total only 0.6% of limbs had a thrombotic event (p < 0.002 in comparison with the other two groups). DVT was asymptomatic in 60% of subjects; 85% of DVTs were observed in passengers in non-aisle seats. Mild gastrointestinal symptoms were reported in 13% of patients taking aspirin. One dose of LMWH is an important option to consider in high-risk subjects during long-haul flights.