Fluid loss does not explain coagulation activation during air travel

Abstract

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.

The impact of long‐haul air travel on variables of the athlete's biological passport

“…In the context of the often discussed risk of DVT during air travel, our data show that several important contributors to the rheology of the blood, such as haemoglobin concentration and haematocrit remain unaffected by travel. This supports the current literature [13]: investigated the impact of fluid loss during a long-haul flight on the coagulation system, but did not find any changes in the investigated markers that would be relevant for an increased risk of DVT. For haematocrit, her results were similar to our study, with a slight decrease over the day as an overall group effect and the vast majority of all participants showing lower values in the evening from an individual point of view (Figure 1).…”

Guidelines on travel‐related venous thrombosis

“…Despite the commonly given advice that travellers should maintain good hydration there is no evidence to support an association between dehydration and the development of VTE (Schreijer et al , 2008).…”

Relation between Air Travel and Venous Thromboembolism

“…On the other hand, Landgraf and colleagues (48) found changes to be within normal physiological limits, and are not enough to cause VTE in healthy individuals. Likewise, no association was found between dehydration and developing VTE, at all (71) .…”