In Space you can turn blood backwards

At 450 kilometers above our heads is the largest scientific laboratory that humanity has ever built outside the Earth: the International Space Station (ISS). The astronauts who live there conduct experiments and scientific tests of all kinds every day and they are themselves guinea pigs: the study of the effects of Space on their health is in fact precious to understand how our body adapts to weightlessness , in view of long-lasting space missions on the Moon and perhaps one day on Mars. And it is thanks to some of these tests that the researchers here on Earth have discovered that astronauts can suffer from thrombosis, a very risky blood circulation disorder; this side effect could affect the way the crews live and work during their space missions.

In recent years, thanks to long-standing missions on the ISS – which involve life in orbit for at least six months – researchers have discovered many things about the effects of weightlessness on our body, which went unnoticed in previous decades when the missions had a shorter duration. For example, many astronauts return from orbit with their eyeballs slightly flattened, the optic nerve swollen and some consequent vision problems, so much so as to have pushed NASA to provide glasses with different shades for astronauts who gradually suffer a deterioration of vision . The effect is temporary and disappears after a few weeks from the time of return: the researchers suspect that the cause is an accumulation of liquids in the head, due to the absence of weight, and the difficulty that our body encounters in making them circulate normally in the rest of the body.

The suspicion has led to various scientific research to find confirmation of changes in circulation. Karina Marshall-Goebel, a NASA researcher, started a program to monitor the astronaut's jugular vein with other colleagues. The jugular (internal) is located in the neck and has the task of draining the blood – now devoid of most of the oxygen – from the brain to the heart together with the other jugular veins. Its function is essential to ensure that the circulatory system brings oxygenated blood to neurons, brain cells, and take away cellular waste and carbon dioxide.

The study involved a total of nine astronauts and two astronauts, whose names were not disclosed for privacy reasons. Before they left for the ISS in their respective missions, they had been subjected to tests to measure blood flow in their jugular veins under different conditions: sitting, lying down and on an inclined plane. The test is not very complicated to perform and requires the use of a knob that rests on the neck to perform an ultrasound of the jugular. All the participants had passed the exam without problems on Earth, indicating a correct blood supply through the vein, one of the largest blood vessels passing through the neck.

Things went differently on the International Space Station, where the astronauts had the task of periodically repeating the exam to assess any variations, led by researchers on our planet. In five out of eleven astronauts blood stagnation was found: in some cases it flowed slightly towards the heart to then reverse the sense and return to the brain. It is rare for such a condition to occur in the jugular vein, while it can sometimes occur in the veins of the legs: for example, it is a problem for those facing long air journeys and sitting for many hours.

When blood stagnates in a vessel, a thrombus can form, a solid mass that forms on the endothelium, the inner surface of blood vessels. The permanence and turbulence in the flow cause the fibrous components of the blood to remain in contact with the endothelium for a long time, causing the processes leading to coagulation to activate. Usually the problem resolves by itself thanks to other substances that favor the dissolution of the thrombi, avoiding that they become large and dangerous for the health. If a thrombus does not dissolve completely, it can detach from the endothelium, continue the journey in the blood vessels and also do serious damage to some organs, such as the lungs (pulmonary embolism).

As the researchers explain in their study, in two cases the astronauts' blood started to flow in reverse, from the heart to the brain. The hypothesis is that the inversion occurred due to a thrombus that prevented the normal venous flow to the heart, a circumstance that can also occur on Earth in particular thrombosis conditions. Marshall-Goebel used an effective analogy to explain the phenomenon toAtlantic: "It's almost like a detour, like the ones you do when you're driving and you have to go in the opposite direction and then get where you wanted to go."

In one case, an astronaut was performing the Earth-guided test when a thrombus was detected. The NASA doctors then intervened for further remote checks: the astronaut had no particular symptoms, but as a precaution he was prescribed anticoagulant drugs to be taken for the rest of his stay in orbit.

As part of their research, Marshall-Goebel and colleagues asked the astronauts to wear the Russian Chibis coveralls, equipped with special trousers with an aspirator to create a decompression in the legs, in order to counteract the excessive flow of blood towards the head. The suits have helped improve blood circulation in some astronauts, but in other cases they have not been shown to be very effective in reducing the problems detected at the jugular level.

All the astronauts, once back on Earth in normal gravity conditions, have progressively improved by returning to the pre-departure conditions. According to the researchers, this is a further sign of the fact that it is the space environment that conditions the flow of blood and contributes to the formation of thrombi.

Marshall-Goebel does not hide his concern when he saw the first data, but always on theAtlantic he recalled that studies like his serve to evaluate potential risks and to understand how to mitigate them: "I think it was worrying for everyone. But I also think that the fact of having discovered it is a very very positive thing: knowing that it is a risk factor for space travel, it becomes something that can be kept under control and for which prevention can be done ”.

Further research could highlight differences in the incidence of the problem between astronauts and astronauts. Some of them prefer to take the contraceptive pill while on a mission, so they have no problems with the cycle. The pill can promote the formation of thrombi, and therefore the astronauts who use it could be exposed to some more risk.

In light of the research results, NASA is evaluating the launch of a program to keep astronauts in orbit under control, with periodic analyzes to detect risks associated with thrombosis. The flight doctors have also established that anticoagulant drugs and other medicines are always present on the ISS to treat any problems.

The study by Marshall-Goebel and colleagues shows how much there is still to be discovered about the effects of Space on our organism. The greater risk of suffering from thrombi has probably accompanied all the protagonists of space exploration with human beings, and we cannot exclude that without knowing it had also affected the first astronauts who reached the surface of the Moon 60 years ago. Although confined to an orbit of "just" 450 kilometers from the Earth, today's space missions last much longer than those conducted by the Apollo missions at 380 thousand kilometers and this exposes the organism to greater stresses, some of which still to be fully understood.

Thanks to the emergency procedures developed by space agencies, an astronaut who has serious health problems could be brought back to Earth within a few hours by the International Space Station. Things would be more complicated for astronauts who will one day live in the orbital station that NASA plans to build around the Moon, and in a more remote future on Mars. Their return would require days of travel in the first case and months in the second, making therefore necessary interventions directly in the Space. However, astronauts are trained to tackle all major health emergencies during their missions, and can rely on remote medical assistance. We are not made for Space and our body often tries to remind us of it, but all in all we manage quite well.