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

Abstract

Introduction: A recent study investigating astronaut jugular venous flow inflight on the International Space Station (ISS) reported the incidental finding of a persistent asymptomatic obstructive left internal jugular (IJV) venous thrombosis (VT) in a single crewmember1. Furthermore, an additional suspected case was reported following retrospective analysis of the images from the other 11 crew members who participated in the study2 . Venous thrombi can lead to localised pain, redness, distal swelling, venous ischaemia, skin necrosis and even organ dysfunction3 . However, the most significant complication is lung embolization of thrombotic fragments, termed pulmonary embolism (PE) that can lead to cardiorespiratory insufficiency, which can be fatal. Thus, the potential identification of VT, a mission-critical medical condition, in such a highly selected, previously considered low-risk population is concerning and warrants urgent investigation. As a result, the European Space Agency (ESA) supported the creation in 2020 of a ‘Topical Team’ comprising of international subject matter experts in coagulation, venous thrombosis, prophylaxis, and treatment of thrombo-embolic events. The creation of this team was additionally supported by the Cardiovascular, Pulmonary, Renal and Lymphatic Working Group of the ESA SciSpacE roadmap. An operationally focused research strategy is required to define the pathophysiological processes leading to VT presentation in spaceflight, potential clinical presentation, its risk (and the factors that may affect risk), whilst proposing evaluation of candidate diagnostic, mitigation, and management strategies compatible with human spaceflight. The team was supported by individuals familiar with Human Spaceflight medical operations to identify relevant knowledge gaps.