Fluid loss does not explain coagulation activation during air travel.

The mechanism of air travel-related venous thrombosis is unclear. Although immobility plays a pivotal role, other factors such as fluid loss may contribute. We investigated whether fluid loss occurred more in individuals with coagulation activation after air travel than in subjects without. As a secondary aim, we investigated whether fluid loss per se occurred during air travel. In this crossover study, 71 healthy volunteers were exposed to eight hours of air travel, eight hours immobilization in a cinema, and a daily-life control situation. Markers of fluid loss (haematocrit, serum osmolality and albumin) and of coagulation activation were measured before and after each exposure. The study included 11 volunteers with and 55 volunteers without coagulation activation during the flight. The change in parameters of fluid loss was not different in volunteers with an activated clotting system from those without (difference between groups in haematocrit: -0.6%, 95% confidence interval [CI]: -1.9 to 0.6). On a group level, mean haematocrit values decreased during all three exposures. However, in some individuals it increased, which occurred in more participants during the flight (34%; 95% CI 22 to 46) than during the daily-life situation (19%; 95% CI 10 to 28). These findings do not support the hypothesis that fluid loss contributes to thrombus formation during air travel.

Desloratadine shows no effect on performance during 6 h at 8,000 ft simulated cabin altitude.

INTRODUCTION: Sustained vigilance is required by pilots and crew during flight; therefore, the use of antihistamines with sedating properties is widely prohibited. The purpose of this study was to determine the effects of desloratadine, a long-acting, nonsedating antihistamine, on healthy volunteers placed under conditions of simulated cabin pressure. METHODS: In a double-blind crossover study, 21 subjects randomly received single doses of desloratadine 5 mg, diphenhydramine 50 mg (active control), and placebo on different days separated by washout periods of 7 d. On test days, predose levels of alertness and fatigue were determined, as were post-dose levels at 1, 2, 3, 5, and 6 h. Measurements included vigilance and tracking, a multi-attribute task battery, the Stanford Sleepiness Scale, and pulse oximetry. RESULTS: Desloratadine had no detrimental effects on sleepiness or performance of tasks associated with flying ability. Conversely, diphenhydramine (active control) caused significantly more sleepiness than did the placebo [F (2,40) = 6.52, p < 0.01], as well as impaired performance (tracking performance p < 0.05 at 3 h post dose), and an increased percentage of omissions (p < 0.05 at 2 h post dose). CONCLUSION: A single dose of desloratadine 5 mg did not cause sleepiness and did not impair the performance of tasks associated with flying ability.