What happens when you have a heart attack on the way to Mars?

Dealing with situations outside the realm of normal human experience is all part of an astronaut’s job description. Still, one can imagine the discomfort felt by the International Space Station (ISS) crew member who received the first diagnosis of venous thrombosis during spaceflight. There is no good time and place to discover a blood clot in your jugular vein, but finding one while you’re more than 200 miles above the Earth is particularly inconvenient.
Helpfully, the ISS was carrying supplies of a blood-thinning medication that could address this potentially life-threatening condition. Still, the astronaut’s dosage had to be cut by a third partway through treatment until more medicine could arrive aboard a supply spacecraft. Several months later, the astronaut – whose identity has not been revealed – returned to Earth and made a full recovery.


This incident, details of which were published in the New England Journal of Medicine in January last year, had a happy ending. That was largely because the astronaut was in regular contact with healthcare professionals here on Earth and could be resupplied with medication. On the first missions to Mars, there will be no resupply vehicles or quick phone calls back to Earth.
“Ultimately, we will have to take some significant risks, particularly if we want to go beyond Earth’s orbit,” says Jonathan Scott, head of the medical projects and technology team at the European Space Agency. “That’s our job, to reduce the risk as far as is reasonably possible.”
That’s not an easy task, because space is a very hazardous place. Even donning a spacesuit puts astronauts at increased risk of drowning and of fingernails falling off. Travelling beyond the Earth’s atmosphere exposes astronauts to radiation, the consequences of which are not fully understood but are unlikely to be good. Weightlessness might be fun but it causes a whole host of problems, including bone and muscle wastage. Some astronauts start losing their sight. All of these issues become more and more acute the longer you spend in space.
On top of that, astronauts face all the health problems we experience on Earth, but without easy access to a hospital. Nasa has a list of around 100 medical conditions judged most likely to occur in space, ranging from toothache and nosebleeds to spine fractures and chemical burns. And while evacuation is possible from the ISS, it gets tricky when you’re on your way to Mars. A round trip to the red planet takes roughly three years, meaning crew members will have to treat each other if there’s a medical emergency along the way.


If your heart stops en route to Mars, rest assured that researchers have considered how to carry out CPR in space. (One option is to plant your feet on the ceiling and extend your arms downwards to compress the patient’s chest.) Astronauts, because of their age range and high physical fitness, are unlikely to suffer a stroke or have their appendix suddenly explode. That’s good because, if it does happen, they’re in the realm of what Scott describes as ‘treatment futility’. In other words: there’s nothing anyone can do about it.
On the ISS, when medical incidents arise, astronauts can draw on the combined expertise of a host of medical experts at Nasa. “The patient is on the space station, the doctor is on the ground, and if there’s a problem the patient consults the doctor,” says Scott. By the time astronauts reach Mars, there’ll be a 40-minute time lag in communications, if it’s possible to make contact at all. “We have to begin preparing for not only being able to diagnose things in spaceflight but also to treat them as well,” Scott says.
Artificial intelligence is likely to be a part of the solution. If you’re imagining the holographic doctor from Star Trek, downgrade your expectations, at least for the next few decades. Kris Lehnhardt, the element scientist for exploration medical capability at Nasa, says: “We are many, many, many years away from: please state the nature of the medical emergency.”
Emmanuel Urquieta is deputy chief scientist at the Translational Institute for Space Health (TRISH), a Nasa-funded program which conducts research into healthcare for deep space missions. While full AI may be a way off, Urquieta believes some form of artificial intelligence will still play a crucial role. “It’s going to be essential for a mission to Mars,” he says. While the crew for a mission to Mars will likely include a medical doctor, he explains: “No single physician can know everything.” And, of course: “What happens if that astronaut gets sick?


Research projects funded by TRISH include Butterfly iQ, a handheld ultrasound device for use by non-medical personnel to make diagnoses that would otherwise require bulky equipment and a trained operator. VisualDx is an AI diagnostics tool originally developed to analyse images and identify skin conditions. The technology is now being adapted to help astronauts diagnose a wide range of conditions most commonly encountered in space, without an internet connection.
Reducing the amount and size of medical equipment, and the level of expertise needed to use it, will be key if we’re going to make it to Mars. Another is maintaining a sufficient amount of consumable medical supplies. At the moment, almost everything astronauts need in space is taken there from Earth. (Much of the drinking water on the ISS is recycled from wastewater that includes the astronauts’ own sweat and urine.)
One Nasa study concluded that a spacecraft heading to Mars should be stocked with 248 litres of intravenous (IV) fluids, taking up a lot of valuable room on a small spaceship. So, over the last decade, Nasa has been working on producing IV fluid from drinking water. Work is ongoing to refine the technology so it can be used for a Mars mission. Lehnhardt says: “You may get to a world where someone has an illness or injury on the way to Mars, and an astronaut flips a switch on the water system, hooks up a bag to a spigot, and five minutes later has a full bag of sterile IV fluid.”
As the blood clot incident on the ISS illustrated, maintaining adequate supplies of medication is also a problem. That’s partly because spacecraft have limited room for a pharmaceutical cabinet, but also because medication degrades faster in space than it does on Earth, potentially because of exposure to radiation. Also, astronauts take a lot of drugs. One 2017 study of astronauts on the ISS found crew members took an average of four medications every week.
Phil Williams is a professor of biophysics at Nottingham University and heads up the world’s first research program in astropharmacy — the study of drugs in space. His team is looking into issues such as the immune system and antibiotic resistance in space, and has sent tiny worms known as nematodes to the ISS, studying how muscles break down in microgravity.
Williams and his colleagues are also investigating how to solve the medication supply issue. “We’re looking at ways to make drugs on-site and on-demand,” says Williams. By taking the protein-building machinery from radiation-resistant bacteria and pairing it with the DNA from protein-based drugs, Williams’s team has succeeded in growing further drug supplies in test tubes. In the future, using 3D printing technology, Williams says we’ll be able to “take a black box and type into the box what you want and out pops the medicine.”
That technology may or may not be adopted for the very first Mars missions. But if humans are ever to colonise other planets, we’ll need to go further than producing medications in space. That might involve 3D printing medical and surgical tools, or even replacement organs; research is currently taking place into whether human hearts can be printed on board the ISS.
Ultimately, working out how to treat medical conditions with minimal resources is essential for deep space exploration, but it also has plenty of terrestrial applications. After all, if we can reduce ‘treatment futility’ in space, we can also minimise it here on Earth. “If we can treat people on Mars, we can treat them anywhere,” says Williams. “In the Antarctic, on a submarine, in a UNHCR camp in Africa, in the local hospital. It doesn’t matter where we are.”
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