Much has been written in the press about air passengers developing deep venous thromboses (DVTs) following long-haul flights. As a result of these reports of ‘traveller's thrombosis’ and several untimely deaths, those flying for over 4 hours are advised to take prophylactic measures, which include ensuring good hydration, restricting alcohol and caffeine intake, and regularly carrying out simple leg exercises including occasional walks during travel.1 Those at particularly high risk are encouraged to consider using graduated elastic stockings and taking a single dose of aspirin or low molecular weight heparin before travel.
We recently came across a 47 year-old female hospital cleaner, with a body mass index of 32 but no other risk factors, who developed a calf DVT 2 days after completing 2 weeks of Crown Court jury service. This involved sitting for an average of 6 hours each day with a 45-minute lunch break which, towards the later stages of the trial, was also spent sitting while deliberating over the verdict. A small twist in the tale is the fact that 10 weeks prior to starting the jury service she had undergone two long-haul flights, each lasting 9.5 hours. It would be difficult to ascertain which events were the most contributory to the development of the venous thrombosis, but current evidence suggests that, in cases of traveller's thrombosis, the symptoms usually develop within 4 days of the flight and certainly within 2 weeks.2
Studies have shown that the main effect of prolonged sitting, and certainly a significant factor in the association between air travel and venous thrombosis, is venous pooling in the calf.3,4 In addition to these haemodynamic responses, measures of rheologic changes in venous blood during prolonged sitting show that 2 hours of quiet sitting can increase thrombotic tendency locally in the leg, but not systemically.5
The patient has subsequently been informed that she may be required for further jury service. This being the case, then she should certainly be advised to take appropriate prophylactic measures. We feel that in any situation where people are to remain sitting for a prolonged period of time (perhaps in excess of 4 hours), they should receive similar advice to those given to airline passengers, particularly when there are several risk factors present.
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- © British Journal of General Practice, 2004.