Surveillance for jugular venous thrombosis in astronauts

Abstract

Background: Thrombosis of the left internal jugular vein in an astronaut aboard the International Space Station was recently described, incidentally discovered during a research study of blood flow in neck veins in microgravity. Given this event, and the high incidence of flow abnormalities, the National Aeronautics and Space Administration (NASA) instituted an occupational surveillance program to evaluate astronauts for venous thrombosis. Methods: Duplex ultrasound of the bilateral internal jugular veins was conducted on all NASA astronauts terrestrially, and at three points during spaceflight. Respiratory maneuvers were performed. Images were analyzed for thrombosis and certain hemodynamic characteristics, including peak velocity and degree of echogenicity. Results: Eleven astronauts were evaluated with matching terrestrial and in-flight ultrasounds. No thrombosis was detected. Compared to terrestrial ultrasound measurements, in-flight peak velocity was reduced and lowest in the left. Six of 11 astronauts had mild–moderate echogenicity in the left internal jugular vein during spaceflight, but none had more than mild echogenicity in the right internal jugular vein. Two astronauts developed retrograde blood flow in the left internal jugular vein. Conclusions: Abnormal flow characteristics in microgravity, most prominent in the left internal jugular vein, may signal an increased risk for thrombus formation in some individuals.

Pathophysiology, risk, diagnosis, and management of venous thrombosis in space: where are we now?

“…However, whether IJV flow was correctly identified as stagnant or retrograde in the initial cohort study, considering the technological limitations and the relative inexperience of crew as sonographers, is unknown 12 . However, a recent update by Pavela et al 13 also documented retrograde IJV flow in 2/11 astronauts undergoing routine venous ultrasound surveillance in flight.…”

“…12 Surgery, LKH Südsteiermark, Wagna, Austria. 13 Department Emergency Medicine, University British Columbia, Vancouver, Canada. 14 Amsterdam UMC location University of Amsterdam, Department of Internal Medicine, Section of Nephrology, Amsterdam, The Netherlands.…”

The Vascular Frontier: Exploring the diagnosis and management of vascular conditions in spaceflight

“…In this issue of Vascular Medicine , Pavela and colleagues report on duplex ultrasound findings in a small cohort of 11 astronauts. 6 They describe abnormal flow characteristics in the internal jugular veins (most prominent on the left) with mild-to-moderate echogenicity of intravenous spontaneous echo contrast, which may be prognostic for thrombus formation and subsequent development of DVT. 6 Such point-of-care ultrasound performed by spaceflight crew members is a valuable tool in the spaceflight medical armamentarium to evaluate and diagnose DVT.…”

“…6 They describe abnormal flow characteristics in the internal jugular veins (most prominent on the left) with mild-to-moderate echogenicity of intravenous spontaneous echo contrast, which may be prognostic for thrombus formation and subsequent development of DVT. 6 Such point-of-care ultrasound performed by spaceflight crew members is a valuable tool in the spaceflight medical armamentarium to evaluate and diagnose DVT. Studies have previously demonstrated that ultrasound evaluation of several conditions can be performed successfully in microgravity, including pneumothorax 7 and sinus fluid levels.…”

“…5 Subsequent sonographic surveillance demonstrated progressive reduction of the thrombus in the left internal jugular vein. Venous thrombosis was previously an unrecognized risk of spaceflight, and Dr James Pavela and colleagues 6 are to be commended on further developing an occupational surveillance program to screen for VTE in spaceflight crew members.…”