The thrombotic risk of spaceflight: has a serious problem been overlooked for more than half of a century?

Abstract

The first ever venous thrombotic condition associated with spaceflight, an internal jugular vein thrombus requiring anticoagulation, has recently been reported. Systematic investigation of space travel-associated thrombotic risk has not been conducted. Cellular, animal, and human studies performed in ground-based models and in actual weightlessness revealed influences of weightlessness and gravity on the blood coagulation system. However, human study populations were small and limited to highly selected participants. Evidence in individuals with medical conditions and older persons is lacking. Evidence for thrombotic risk in spaceflight is unsatisfactory. This issue deserves further study in heterogeneous, high risk populations to find prevention strategies and to enable safe governmental and touristic human spaceflight.

Going against the flow: are venous thromboembolism and impaired cerebral drainage critical risks for spaceflight?

“…Since VT was not previously considered a major risk, contributing risk factors in astronauts are currently insufficiently characterized (5). Aspects such as endothelial dysfunction (11), the influence of mission durations (5), and sex (4) should be investigated and quantified as potential contributing factors for thrombus formation. Screening for thrombophilia and other predisposing clotting factors and correlating these to clinical events or asymptomatic VT in-flight is critical (5).…”

“…Aspects such as endothelial dysfunction (11), the influence of mission durations (5), and sex (4) should be investigated and quantified as potential contributing factors for thrombus formation. Screening for thrombophilia and other predisposing clotting factors and correlating these to clinical events or asymptomatic VT in-flight is critical (5). Finally, gene expression analysis and biochemical markers of coagulation in blood would provide insight into the molecular changes associated with haemodynamic changes.…”

“…Virchow's triad summarizes the three conventional VT risk factors: altered blood flow/stasis, vascular wall injury, and hypercoagulability (10). Venous stasis in the internal jugular vein (IJV), combined with vessel-wall distention could arguably constitute spaceflight associated risk factors for cephalad thrombosis (5,11,12).…”

Cardiovascular autonomic nervous system responses and orthostatic intolerance in astronauts and their relevance in daily medicine

“…Fluid shifts towards the head and fluid redistribution from the intravascular to the interstitial and intracellular spaces contribute to face reddening and swelling-the so-called puffy face-and nose stuffiness in astronauts [29]. The internal jugular vein is dilated and shows stagnant or even retrograde flow in weightlessness [30], which may predispose to neck vein thrombosis [30,31]. More chronically, fluid shifts towards the head may contribute to structural changes in the brain and optic disc edema, which are part of the space-flight neuro-ocular syndrome [32][33][34].…”

Platelets in Wound Healing: What Happens in Space?

“…When entering weightlessness, the astronauts experience an initial increase in central blood volume, followed by intravascular volume contraction due to reduced thirst and increased urine output. Also the increased levels of fibrinogen ẞ chain and the elevated red blood cell counts, both documented in astronauts after long-term spaceflight, might play a role in the formation of thrombi ( Limper et al, 2021 ).…”