Blood Clot In Space: How Did Doctors Treat Astronaut With This Condition?

NASA has learned life-saving lessons that will benefit astronauts on future deep space voyages from a medical emergency involving an astronaut at the International Space Station (ISS) who suffered from a blood clot or a deep vein thrombosis (DVT).

This first-of-its-kind medical episode aboard the ISS was treated by a team of expert doctors diagnosing the patient from the Earth, which is located 200 miles beneath the orbiting ISS. The unidentified astronaut survived, thanks to the team's medical expertise.

The incident is described in a study entitled “Venous Thrombosis during Spaceflight,” which is published in the New England Journal of Medicine. The study authors described how, for the first time, an ISS astronaut’s blood clot was successfully treated by Earth-bound doctors.

The paper’s lead author is Dr. Serena Auñón-Chancellor, clinical associate professor of Medicine at Louisiana State University Health New Orleans School of Medicine's branch campus in Baton Rouge. Auñón-Chancellor, who is also a member of NASA’s astronaut corps, is board certified in both internal and aerospace medicine.

The team included Dr. Stephan Moll, an expert in thrombosis at the University of North Carolina School of Medicine, who was brought in by NASA to help treat the astronaut. Dr. Moll, Dr. James Pattarini of NASA’s Johnson Space Center and Dr. Ashot Sargsyan of KBR in Houston, were the co-authors of the paper.

The team's successful treatment of the astronaut’s blood clot in the internal jugular vein inspired more research on travel in zero-gravity and also encouraged a wider use of telemedicine. According to NASA, the astronaut detected the blood clot while doing neck ultrasound examinations as part of a NASA study on the effects of weightlessness on blood flow. The discovery of the potentially perilous condition in the distant and weightless environment of space called for a quick determination of what action to take.

“On Earth we would feel comfortable just observing the person and not treating with blood thinners, because if things get worse, you can always do some intervention,’’ Dr. Moll said. “There are emergency rooms here, but in space you don’t have that option.’’

Dr. Moll said blood clots aren't always dangerous and usually dissolve on their own. They sometimes develop on the legs of passengers traveling long stretches in cramped conditions.

After assessing the risk of various outcomes against the likelihood the astronaut may bleed from an injury, the team decided to treat the patient with blood thinners, of which the ISS had a few on hand. New dosages and a supply of apixaban (an oral anticoagulant) arrived 43 days later via a supply spacecraft.

The astronaut was treated with injectable enoxaparin (a heparin-like blood thinner), with the dosage reduced after 33 days. This meant the supply of this blood thinner lasted until the arrival of apixaban. Scientists also sent anti-coagulation reversing agents on the supply spacecraft.

After the astronaut’s return to Earth, an ultrasound revealed the clot had flattened. This meant no further anticoagulation was needed. The clot remained for 24 hours after the astronaut's return but dissolved 10 days later. The astronaut was asymptomatic six months after his return from space.

This medical emergency convinced the team to say further research is needed on changes in blood organization and flow in space.

"These new findings demonstrate that the human body still surprises us in space," Auñón-Chancellor said. "We still haven't learned everything about Aerospace Medicine or Space Physiology."

The team said its clinical case study published in the New England Journal of Medicine about the deep vein thrombosis episoide on the ISS highlighted how blood flows from the brain in microgravity are important medical findings.

NASA agreed and said it's committed to monitoring blood flow dynamics to protect astronauts’ health and performance in current International Space Station missions and future missions to the Moon and Mars. It said it will continue to monitor future astronauts for blood flow stasis with routine on-orbit screening ultrasounds and has ensured the International Space Station is equipped with appropriate treatments in the medical kit available to crew members.