What happens when you get sick or injured in space, thousands of miles from the nearest
hospital?
Space flight is incredibly risky and an astronaut getting sick might mean they don't survive
the mission.
So how does NASA prepare for these situations?
Earlier this year, I came across a letter to the editor of the New England Journal of
Medicine.
In that letter, some NASA scientists told the story of how an anonymous NASA astronaut
was found to have a clot in the internal jugular vein of the neck during a spaceflight mission.
The internal jugular vein is the largest vein in the neck and it drains blood from the brain
and face.
This particular astronaut was participating in a study where they were using ultrasounds
to investigate fluid shifts in spaceflight.
The ultrasound pictures were sent to Earth and to the surprise of two radiologists at
NASA, they found there was a huge thrombus, or blood clot, partially occluding the vein.
The strange thing is that the astronaut didn’t have the usual risk factors for blood clots
to occur.
In medicine, we talk about Virchow’s triad to describe the causes of a thrombosis.
The triad consists of injury to the blood vessels, hypercoagulability and reduced blood
flow.
Hypercoagulability occurs in people with congenital clotting disorders, cancer, sepsis and in
pregnant mothers or smokers.
In this case, all those things were unlikely so we can rule them out.
Also, there probably wasn’t any injury to the blood vessels as that usually occurs from
trauma, surgery or chronic hypertension.
However, since the astronaut wasn’t experiencing any gravity, there was less blood draining
from the head back to heart.
As a result, the blood in this astronaut’s internal jugular vein was stagnant and when
that happens platelets in the blood are more likely to clump together and form clots.
On Earth, this often happens in the legs when people are bed bound after surgery or on a
long-haul flight.
The clot in the legs can travel to the lungs and cause something called a pulmonary embolism,
or PE for short.
If it’s big enough, PEs can be life-threatening because the clot blocks blood from reaching
the lungs and carrying oxygen to the rest of the body.
So in the NASA astronaut, because of the lack of gravity and lack of blood flow, NASA doctors
were worried that the same thing would happen where the clot travels to the lungs and causes
a PE.
The other possibility is that the clot could grow and extend upwards into the brain and
block blood flow that way, effectively causing a stroke.
When an astronaut gets an emergency medical problem aboard the International Space Station,
their first option is to throw that astronaut into a space capsule and fly them back to
Earth.
However, if our astronaut with the blood clot was flown back to Earth, it would cause a
lot of turbulence and G-forces which could lead to bits of the clot breaking off and
causing a pulmonary embolism.
Luckily there was a 40-day supply of an injectable anti-clotting medication called enoxaparin
on board the ISS.
NASA also decided to send a resupply vehicle to the ISS to deliver more oral anti-clotting
medications.
What’s crazy is that when the astronaut landed back on Earth 6 months into his mission,
normal blood flow resumed in the vein and the clot disappeared within 10 days.
This brings us to challenges of medical care in space.
Just as one example, the zero gravity environment means that bubbles don’t float to the top
in fluids or liquid medications.
It makes drawing up medications difficult and if you draw up air you could potentially
inject that into the veins causing a pulmonary air embolus just like what we were talking
about before but with air.
Even seemingly simple things, like giving IV fluids requires gravity for the fluid to
flow, so in space you would need to physically pump it into the veins.
If there’s an acute medical condition like appendicitis in space, the astronaut needs
to be flown back to Earth as soon as possible.
Or the astronauts might need to perform surgery with the help of an Earth doctor through video
call maybe.
However, performing emergency surgery in space has it's own problems.
Once the body is opened, blood and other fluids will form little bubbles because of surface
tension and these bubbles float around and can disrupt equipment or block the surgeons
view.
One paper proposed an idea where they used an air-tight dome over a body cavity to give
the person doing the surgery a clear view of what's going on inside without letting
fluid escaping.
The dome is flexible and the astronaut could make small holes to basically do keyhole surgery
much like how it’s done on earth.
In fact, NASA funded an experiment where they put surgeons on something called a parabolic
flight which is a plane that sort of falls towards Earth for a short duration just to
simulate the zero-gs.
They asked the surgeons on the parabolic flight to perform laparoscopic surgery on animals.
What they found was that it is was no harder than doing surgery in a normal 1-g environment.
In fact, there’s heaps of other studies that have demonstrated that it’s entirely
possible to do things like microscopic surgery, intubations, vascular surgery and a bunch
of other weird and wonderful procedures in zero-gs.
However, then it becomes the problem of how you’re going to transport all that surgical
equipment up to space when it costs about $10,000 per pound to launch that cargo.
One possible solution is to use 3D printers to print out the instruments when they’re
needed but as you could imagine this comes with its own problems like lengthy printing
times.
And secondly, you have to train your astronauts to be able to perform these surgeries which
is no easy feat.
Scientists have also proposed the idea of robot surgeons, like if there was a surgeon
on Earth controlling a robot in space.
NASA actually tested this by performing a gallbladder removal operation where the surgeon
controlled a robot 14km away in an underwater facility.
This might work for missions close by like in the ISS but for spaceflights that are further
away, the lag time for the information to travel might be too much.
So you might be thinking, why don’t we just remove everyone’s appendixes and gallbladders
before they go up into space?
At the moment for astronauts in the ISS, flying back to Earth can be done relatively quickly
so it’s probably not worth it.
However, there’s a study done in 2012 which says the astronauts going on long-haul flights,
say to Mars, might actually benefit from having their appendixes or gallbladders removed.
Emergency medical care in space poses a huge challenge.
We might not even fully understand how our bodies will react to surgery in zero-gs considering
there’s a lot of fluid shifts and hemodynamic changes that go on in space.
You know, space does some crazy things to your body.
First we found that it causes your bones and muscles to waste away, then it became problems
with your heart deconditioning.
Only within the last 10 years we found out about this thing called spaceflight associated
neuro-ocular syndrome where astronauts’ have deteriorating vision because of physical
changes to their retina and optic nerves.
Finally, this time last year, we didn’t even know that astronauts could be developing
these huge clots in their necks.
All this is to say is who knows what other healthcare challenges lie ahead for future
astronauts.
One thing is for certain though, and that is science will keep evolving to overcome
these obstacles and push humans to places we’ve never been before.