Astronaut Aboard ISS Diagnosed With Blood Clot In First Telemedicine Treatment Of Its Kind

A depiction of the space shuttle docked at the International Space Station orbiting Earth. Marc Ward/Shutterstock

Having a medical issue while hurtling 320 kilometers (200 miles) above Earth aboard the International Space Station (ISS) is not ideal. To boot, the astronaut in question was diagnosed with a rather serious condition: deep vein thrombosis, a blood clot in the internal jugular vein of their neck. While on Earth the treatment is rather straightforward, aboard the ISS some long-distance telemedicine was in order. 

"My first reaction when NASA reached out to me was to ask if I could visit the International Space Station (ISS) to examine the patient myself," said Stephan Moll, a UNC School of Medicine blood clot expert, in a statement. "NASA told me they couldn't get me up to space quickly enough, so I proceeded with the evaluation and treatment process from here in Chapel Hill."

The astronaut was one of 11 involved in a vascular study observing physiological changes to the body in space during long-term spaceflight. The patient's identity is being kept private, so information on when this happened has not been included in the case study. We do know that they were two months into a six-month mission and they have since returned to Earth.  

An ultrasound examination revealed a left internal jugular venous thrombosis. The astronaut experienced no headache or facial plethora (red face) symptoms prior to diagnosis. Molls is a DVT expert here on Earth, but with his bid to go to the station denied, a more creative – and delicate – approach was needed. 

"Normally the protocol for treating a patient with DVT would be to start them on blood thinners for at least three months to prevent the clot from getting bigger and to lessen the harm it could cause if it moved to a different part of the body such as the lungs," Moll said. "There is some risk when taking blood thinners that if an injury occurs, it could cause internal bleeding that is difficult to stop. In either case, emergency medical attention could be needed. Knowing there are no emergency rooms in space, we had to weigh our options very carefully."

Dr. Stephan Moll at NASA.

To make treatment more tenuous, there are limited medical supplies aboard the ISS. Molls and a team of NASA doctors decided on the blood thinner Enoxaparin (Lovenox®) while a new shipment of drugs was sent to the station. Treatment started with a daily injection of 1.5 milligrams per kilogram of body weight, which was reduced to 1 milligram after 33 days to extend therapy until oral apixaban could be delivered via a supply spacecraft. The clot was monitored with self-performed ultrasounds on the neck. At 7- to 21-day intervals, the blood clot showed progressive reduction. 

"When the astronaut called my home phone, my wife answered and then passed the phone to me with the comment, 'Stephan, a phone call for you from space.' That was pretty amazing," said Moll. "It was incredible to get a call from an astronaut in space. They just wanted to talk to me as if they were one of my other patients. And amazingly the call connection was better than when I call my family in Germany, even though the ISS zips around Earth at 17,000 miles per hour."

Prior to re-entry back to Earth, the astronaut stopped taking their medication due to the demanding physical nature of the process  They landed safely and while follow-up examinations revealed a small residual blood clot 24 hours post-return, no clot was found 10 days after. They required no more treatment thereafter, according to the report in The New England Journal of Medicine.  

The case highlights the complexities of space medicine, particularly whether the condition was exacerbated by space travel or whether it would have occurred similarly here on Earth too.

"Is this something that is more common in space?" posed Moll. "How do you minimize risk for DVT? Should there be more medications for it kept on the ISS? All of these questions need answering, especially with the plan that astronauts will embark on longer missions to the Moon and Mars.”

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