Blood may clot or flow backwards in space

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A new NASA report suggests that astronauts can have significant blood flow problems in the upper body and the head specifically. 

This unexpected discovery has important implications for long-range space missions, including voyages to Mars.

It’s true that for decades scientists have gathered data documenting the harsh effects space travel has had on the human body.

They have observed how the reduction of gravity (to zero gravity) causes muscles to lose mass and bones to become significantly more fragile.

Astronauts also experience the loss of blood volume, a weakened immune system and cardiovascular de-conditioning since floating requires little effort and the heart does not have to work as hard to pump blood.

This new study uncovers a major problem we didn’t have in the past: a blood vessel on the side of the neck that is responsible for draining blood from the face, brain and neck. 

Spending time in space can affect the way blood flows through the internal jugular vein, causing blood to stop or even flow backwards, a health risk that was unknown until now. 

In a study conducted at the space agency, scientists examined 11 healthy astronauts who had remained aboard the International Space Station for an average of six months. 

During routine ultrasound evaluations on the 50th day of their mission, they discovered that seven crew members had stagnant or inverse blood flow in the left internal jugular vein.

They also found that one astronaut developed a clot in the internal jugular vein during the space flight, and another crew member also had a partial clot after returning to Earth, according to the research.

This is the first time scientists have observed these conditions in astronauts and the implications of their discovery could affect future long-term space flight, such as the proposal to put humans on Mars in the near future. 

A manned mission to Mars could take up to 400 days, even if the mission involves little or no stay on the surface of the Red Planet. 

Recently, NASA scientists have also expressed concern about the risk of radiation from energetic particles in long-term space missions.

According to the researchers of this study, this problem must be investigated before astronauts can begin long journeys to Mars. It is not yet clear what the consequences of this type of thrombosis might be, but the implications could be serious and even fatal.

"Exposure to a weightless environment during space flight results in a chronic change in blood and tissue fluid compared to upright posture on Earth, with unknown consequences for cerebral venous flow," the authors expose.

Here on Earth, of course, gravity does the work of drawing blood from the head to the rest of the body: it's one of the reasons why you'd start to feel so strange if you did a headstand for a long period of time.

"Liquid changes to the head during prolonged weightlessness cause facial swelling, decreased leg volume, increased systolic volume, and decreased plasma volume," experts continue.

Needless to say, more research is needed to determine how large this problem is and how we might mitigate it in future space flight.

Reference: Evaluation of jugular venous blood flow stasis and thrombosis during space flight. Cardiology. KarinaMarshall-Goebel,PhD1;Steven S.Laurie,PhD1;Irina V.Alferova,MD, PhD2;et al JAMA Netw Open.2019;2(11):e1915011. DOI: doi:10.1001/jamanetworkopen.2019.15011

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