Images of Hyperthyroidism: Graves Disease

September 1, 2006

Recently, a well-designed crossover study assessed the risk of thrombosis during long flights.1,2 Included were persons with such risk factors as factor V Leiden mutation and oral contraceptive use. All 71 patients (15 men, 56 women) were studied (not randomized) in each limb of the protocol--in random order--during each of the following: an 8-hour flight, 8 hours spent watching movies, and 8 hours of typical daily living. Fifteen of the participants took oral contraceptives, 11 had the factor V Leiden mutation, and 15 had both risks.

What steps can my 68-year-old patient take to help prevent thrombosis on a 14-hour plane flight?

Recently, a well-designed crossover study assessed the risk of thrombosis during long flights.1,2 Included were persons with such risk factors as factor V Leiden mutation and oral contraceptive use. All 71 patients (15 men, 56 women) were studied (not randomized) in each limb of the protocol--in random order--during each of the following: an 8-hour flight, 8 hours spent watching movies, and 8 hours of typical daily living. Fifteen of the participants took oral contraceptives, 11 had the factor V Leiden mutation, and 15 had both risks.

The investigators measured markers of an activated coagulation and fibrinolytic system (thrombin-antithrombin complex, D-dimer, and prothrombin fragments 1 and 2). The researchers were blinded to the patients' status when the blood was drawn and the results were tabulated.

AIR TRAVEL AND THROMBOSIS: WHAT THE EVIDENCE SHOWS

Thrombin-antithrombin complex levels increased an average of 30% after the 8-hour flight but decreased after marathon movie watching (by 2%) and after daily activities (by 8%). Levels of markers of stimulated coagulation were highest during flight in participants with factor V Leiden mutation who used oral contraceptives. The results clearly demonstrated that air travel for 8 hours increases coagulant activity.

Why might air travel be different from other situations characterized by varying degrees of inactivity? It may be that sitting in one place and the hypobaric hypoxemia of modern air travel have a synergistic effect.

WHAT TO TELL PATIENTS

Reassure patients that age and other risk factors do not preclude long plane flights. Although a previous study found that prophylactic aspirin was unsuccessful in reducing the risk of thrombosis,3 some simple measures may help. Alcohol and sedatives increase immobilization and may heighten risk; thus, they should be avoided. Performing intermittent calf contractions and getting up occasionally may be helpful. In some high-risk patients, compressive stockings are a reasonable option. Further study may identify travelers, such as those with recent joint replacement, who may benefit from prophylactic heparin. *

References:

REFERENCES:

1.

Schreijer AJ, Cannegieter SC, Meijers JC, et al. Activation of coagulation system during air travel: a crossover study.

Lancet.

2006;367:832-838.

2.

Stricker H. Clotting in the air.

Lancet.

2006;367:792-793.

3.

Cesarone MR, Belcaro G, Nicolaides AN, et al. Venous thrombosis from air travel: the LONFLIT3 study--prevention with aspirin vs low-molecular-weight heparin (LMWH) in high-risk subjects: a randomized trial.

Angiology

. 2002;53:1-6.

FOR MORE INFORMATION ABOUT TRAVEL-RELATED DISORDERS:

m www.cdc.gov/travel