In case you hadn’t noticed, we live in a dangerous world. While our soft, fleshy selves are remarkably good at absorbing kinetic energy and healing the damage that results, there are very definite limits to what we humans can deal with, beyond which we’ll need some help. Car crashes, falls from height, or even penetrating trauma such as gunshot wounds — events such as these will often land you in a trauma center where, if things are desperate enough, you’ll be on the operating table within the so-called “Golden Hour” of maximum survivability, to patch the holes and plug the leaks.
While the Golden Hour may be less of a hard limit than the name implies, it remains true that the sooner someone with a major traumatic injury gets into surgery, the better their chances of survival. Here on planet Earth, most urban locations can support one or more Level 1 trauma centers, putting huge swathes of the population within that 60-minute goal. Even in rural areas, EMS systems with Advanced Life Support crews can stabilize the severely wounded until they can be evacuated to a trauma center by helicopter, putting even more of the population within this protective bubble.
But ironically, residents in the highest-priced neighborhood in human history enjoy no such luxury. Despite only being the equivalent of a quick helicopter ride away, the astronauts and cosmonauts aboard the International Space Station are pretty much on their own when it comes to any traumatic injuries or medical emergencies that might crop up in orbit. While the ISS crews are well-prepared for that eventuality, as we’ll see, there’s only so much we can do right now, and we have a long way to go before we’re ready to perform surgery in space
Stacking the Deck
In the relatively short time that humans have been going to space, we’ve been remarkably lucky in terms of medical emergencies. Except for the incidents resulting in total loss of ship and crew, on-orbit medical events tend to be few and far between, and when they do occur, they tend to be minor, such as cuts, abrasions, nasal congestion, and “space adaptation syndrome,” a catch-all category of issues related to getting used to weightlessness. On the more serious end of the spectrum are several cases of cardiac arrhythmias, none of which required interventions or resulted in casualties.
There are a few reasons why medical incidents in space have been so few and far between. Chief among these is the stringent selection process for astronauts and cosmonauts, which tends to weed out anyone with underlying problems that might jeopardize a mission. This means that everyone who goes to space tends to be remarkably fit, which reduces the chance of anything untoward happening in orbit. Pre-flight quarantines are also used to keep astronauts from bringing infectious diseases up to orbit, where close quarters could result in rapid transmission between crew members.
Also, once these extremely fit individuals get to orbit, they’re among the most closely medically monitored people in history. Astronauts of the early Space Race programs and into the Shuttle program days were heavily instrumented, with flight surgeons constantly measuring just about every medical parameter engineers could dream up a sensor for. Continuous monitoring of crew vital signs isn’t really done much anymore, unless it’s for a particular on-orbit medical study, but astronauts are still better monitored than the average Joe walking around on the ground, and that offers the potential to pick up on potential problems early and intervene before they become mission-threatening issues.
Strangely enough, all this preoccupation with mitigating medical risks doesn’t appear to include the one precaution you’d think would be a no-brainer: preflight prophylactic appendectomy. While certain terrestrial adventures, such as overwintering in Antarctica, require the removal of the appendix, the operation isn’t mandated for astronauts and cosmonauts, probably due to the logic that anyone with a propensity toward intestinal illness will likely be screened out of the program before it becomes an issue. Also, even routine surgery like an appendectomy carries the risk of surgical complications like abdominal adhesions. This presents the risk of intestinal obstruction, which could be life-threatening if it crops up in orbit.
Mechanisms of Injury
Down here on Earth, we have a lot of room to get into trouble. We’ve got stairs to fall down, rugs to trip over, cars to crash, and through it all, that pesky acceleration vector threatening to impart enough kinetic energy to damage our fragile shelves. In the cozy confines of the ISS or any of the spacecraft used to service it, though, it’s hard to get going fast enough to do any real damage. Also, the lack of acceleration — most of the time — eliminates the risk of falling and hitting something, one of the most common mechanisms of injury here on Earth.
Still, space is a dangerous place, and there is an increasing amount of space debris with the potential to cause injuries. Even with ballistic shielding on the ISS hull and micrometeoroid protection built into EVA suits, penetrating trauma is still possible. Blunt-force trauma is a concern as well, particularly during extravehicular activities where astronauts might be required to handle large pieces of equipment; even in free-fall, big things are dangerous to be around. Bones tend to demineralize during extended spaceflights, too, meaning an EVA could result in a fracture. EVAs can also present cardiac risks, with the stress of spacewalking potentially triggering an undetected and potentially serious arrhythmia.
Another underappreciated risk of spaceflight is urological problems. Fred Haise, lunar module pilot for the doomed Apollo 13 mission, famously developed a severe urinary tract infection due to the stress and dehydration of the crew’s long, cold return to Earth. Even in routine spaceflights, maintaining adequate hydration is difficult; coupled with excessive urination caused by the redistribution of fluids and increased excretion of calcium secondary to bone demineralization, kidney stones are a real risk.
Kidney stones aren’t just a potential problem; they have happened. A cosmonaut, reportedly Anatoly Solovyev, developed symptomatic kidney stones during a Mir mission in the 1990s. Luckily, he was able to continue the mission with just fluids and pain medications, but kidney stones can be excruciatingly painful and completely debilitating, and should a stone cause an obstruction and urinary retention, it could require surgery to resolve.
The Vertical Ambulance Ride
Given all these potential medical risks, is the ISS equipped for surgical interventions? In a word: no. While ISS crew members undergo extensive medical training, and the station’s medical kit is well-stocked, no allowance has been made for even the simplest of surgical procedures in orbit. The reasoning is simple: with at least one Soyuz or Dragon capsule berthed at the station at all times and a small, low-risk population aboard, the safest approach to a major medical issue is to evacuate the patient back to Earth.
That’s easier said than done, of course. Launching a Soyuz or Crew Dragon from the ISS takes a minimum of three to six hours, and potentially longer if a severely injured astronaut cannot easily don the required pressure suit. Recovery time once the capsule lands could be prolonged for an unplanned lifeboat return; adding in transport time to a medical facility, it could be six hours or more before advanced treatment can begin.
To make sure the astronaut survives what amounts to a protracted and very expensive ambulance ride, the crew will attempt to stabilize the patient as best as possible. The designated crew medical officer (CMO) has training in starting IVs, performing endotracheal intubation, and even thoracocentesis, or the placement of a chest tube. On top of the medications available in the station med kit and with help from flight surgeons on the ground, the crew should be able to stabilize the patient well enough for the ride home.
Practice Makes Perfect
Obviously, though, the medevac strategy only works if the accident occurs close to Earth. As we push crewed missions deeper into space, evacuation will likely be off the table, and even with a crew carefully curated for extreme fitness, eventually the law of averages will catch up to us, and it will become necessary to perform surgery in space. And even though that first space surgery will likely be performed under emergent conditions, probably by an untrained crew, that doesn’t mean future space surgeons will be flying completely blind.
Back in 2016, a multidisciplinary group in Canada undertook a unique comparative study of simulated surgery under weightless conditions. Using a Dassault Falcon 20 Research Aircraft — essentially Canada’s version of NASA’s famous “Vomit Comet” — a team of ten surgeons took turns performing a common trauma procedure: surgical hemorrhage control of an exsanguinating liver laceration. Such an injury could easily occur in space, either through blunt-force or penetrating trauma, especially on a mission that would include any sort of construction tasks.
The goal of the trial was to compare simulated blood loss between surgery performed in zero-g conditions and the same operation performed on the ground. A surgical simulator called a “Cut Suit,” which looks and acts like a human torso, was secured to a makeshift surgical table in the cramped confines of the Falcon — a good simulation of what will likely be the cramped quarters of any future interplanetary spacecraft. The surgeon and an assistant were secured in a kneeling position in front of the simulator using bungee cords, along with a technician charged with maintaining a simulated blood pressure of 80 mm Hg in the Cut Suit.
For the zero-g surgery, the Falcon flew parabolic paths that resulted in 20-second bursts of weightlessness. All airborne surgical tasks were performed only during weightlessness; for the 1-g operation, which was performed with the same aircraft parked in a hangar, the surgeons were limited to 20-second work windows at the same cadence as the zero-g surgery. The surgeries were extensively documented with video cameras for post-surgical review and corroboration with simulated blood flow measurements during the procedures.
The results were surprisingly good. All ten surgeries were completed successfully, although two surgeons had to tap out of the final closing task to keep from vomiting into the surgical field. Although all surgeons reported that the zero-g surgery was subjectively harder, objective results, such as blood loss and time needed to complete each surgical task, were all at least slightly better at zero-g than 1-g. It needs to be stressed that even for simulations, these were simplified surgeries, perhaps overly so. There was no attempt at infection control; no draping of the patient or disinfection of the field, no gowning or scrubbing, and no aseptic procedure while handling of instruments. Also, there was no simulated anesthesia, a critical step in the procedure. But still, it suggests that the basic mechanics of one kind of surgery could be manageable under deep-space conditions.
Aside from testing more realistic surgical procedures under zero-g, more testing will be required to see what weightless post-op and recovery look like. The operation selected for the trial was somewhat incomplete because packing a liver wound isn’t really an endpoint in itself, but more of a stop along the way to recovery. Packing is just what it sounds like — absorbent material packed around the wound to staunch the flow of blood and to provide some direct pressure to allow blood to clot so the wound can heal naturally. The packing material will have to be removed eventually, and while it’s possible to remove it via surgical drains placed during the packing operation, it’s more likely that another open-field or at least a laparoscopic operation will be needed to take the packing material out and tidy up any wounds that haven’t healed by themselves.
The placement of surgical drains also brings up another problem of zero-g surgery. In terrestrial surgery, drains are generally placed in locations where blood and fluids are expected to pool. For the liver packing example, drains would generally be placed posterior to the liver, since the patient would be lying in bed during recovery and the blood would tend to pool at the back of the peritoneal cavity. In space, though, how those fluids would be removed is an open question. Exploring that question might be difficult; since recovery takes days or even weeks, it would be hard to simulate in 20-second bursts. Artificial gravity might help with wound drainage, but the effects of the Coriolis force on the healing process would have to be explored, too.
Given that we’ve been doing surgery here on earth for thousands of years, it’s surprising to have question marks for doing exactly the same things in microgravity. But for surgery, space still remains the final frontier.
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