Treating a Blood Clot in Space

Updated: Feb 25, 2020

One day, NASA discovered that an astronaut aboard the ISS had a deep vein thrombosis (DVT) or blood clot in the jugular vein in the neck. However, he was asymptomatic so no one was aware of the clot. The DVT was discovered when the astronaut was taking ultrasounds of his neck for a research study on how body fluid is redistributed in zero gravity.

When the clot was discovered, NASA consulted with Stephen Moll, MD, at the University of North Carolina (UNC) School of Medicine, and a member of the UNC Blood Research Center. NASA wanted to know how to proceed with the treatment process by consulting with the doctor on earth since it was not possible to get the patient back from space quickly enough and it was also thought that he might not survive the difficult return to earth due to the clot.

This was the first time a blood clot has been found in an astronaut in space, so there wasn’t an established method of treatment for DVT in zero gravity. Dr. Moll working along with a team of NASA doctors decided blood thinners would be the best course of treatment for the astronaut.

They were limited in their pharmaceutical options, since the ISS keeps only a small supply of various medicines on board, and as a result, there was a limited amount of the blood thinner Enoxaparin available. The doctor in Chapel Hill advised NASA on the dosage of Enoxaparin needed to effectively treat the DVT while waiting for NASA to get a new shipment of drugs to the ISS. The treatment with Enoxaparin lasted for about 40 days. On day 43, a supply of Apixaban was delivered to the ISS by a supply spacecraft.

The astronaut was able to perform ultrasounds on his own neck with guidance from a radiology team on Earth to monitor the blood clot. Dr. Moll was able to speak to the astronaut during this period via emails and phone calls.

Four days before the astronaut’s return to Earth, he was advised to stop taking Apixaban. The doctor and his NASA counterparts made the decision because of how physically demanding and potentially dangerous the re-entry process can be for astronauts. They did not want an injury to be exacerbated by the use of blood thinners. Fortunately, the astronaut landed safely on Earth and the blood clot required no additional treatments.

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