Imagine a medical emergency on a flight to the moon, an asteroid or Mars—it may not be as catastrophic as the crisis in the film Gravity, but perhaps an astronaut is bleeding. Surgery can always be challenging, but it would be even more so in microgravity, because blood droplets can float, potentially obscuring a caregiver’s field of view. Now researchers have tested a novel way to potentially control bleeding during surgery in space by isolating wounds under transparent watertight domes filled with fluid.
Disasters have occurred in spaceflight, but no incident has required surgery in space—yet. If astronauts need medical attention, they can return to Earth relatively quickly if they are in low Earth orbit—for instance, from the International Space Station, they could be on the ground possibly within 24 hours via Russian Soyuz spacecraft that are always docked at the station.
"When it comes to exploration-class spaceflight to destinations such as the moon, an asteroid or Mars, however, there can be significant risks to health over the long times these expeditions can take, and surgery may become necessary," says researcher George Pantalos, professor of surgery and biomedical engineering at the University of Louisville in Kentucky. President Obama has called on NASA to send a manned mission to a near-Earth asteroid by 2025 and to Mars in the 2030s. A round-trip to an asteroid could take months, whereas one to Mars could take three years.
For the past three decades scientists have explored ways surgery could be performed in space. The main problem is that sans gravity, blood could drift into the eyes, nose and throat as well as potentially spread disease among the crew. It could also splatter inside spacecraft cabins and perhaps muck up vital electronics. In 1984 researchers reported one system that would essentially wrap plastic bags around wounds to attempt to control bleeding, and another tested in 1993 would fully enclose patients in rigid transparent boxes. Surgeons could stick their hands and tools into either containment system to operate. A critical shortcoming of both strategies was that blood could paint the container walls and obscure the view.
Neurosurgeon James Burgess at Allegheny General Hospital in Pittsburgh came up with the idea of placing a transparent dome over a wound and then filling it with fluid such as saline solution. The fluid’s pressure could slow and even stop bleeding until a surgeon can seal the wound. "A hydrostatic pressure is like a force field—it's what a science fiction writer might imagine," says researcher James Antaki, a biomedical engineer at Carnegie Mellon University. "The idea is simultaneously revolutionary and common sense, the definition of an inventive solution to the problem, like the upside-down ketchup bottle."
Ports in the dome could allow insertion of conventional or endoscopic surgical tools. Moreover, "a suction tool can also be directed to where the bleeding is to clear the surgeon's field of view," Pantalos says.
Although Burgess originally came up with the idea to help keep delicate tissues from drying out during brain and spinal surgery, along with control profuse bleeding that can happen during operations, Pantalos and his colleagues reasoned this Aqueous Immersion Surgical System (AISS) could also help in microgravity. "We have begun to feel satisfied that the concept is applicable in almost in any surgical situation—on Earth or in space," Burgess says.
The AISS poses a number of tricky challenges. For instance, the researchers want to maintain constant pressure under the dome when suctioning blood away by pumping in fluid at roughly the same rate—otherwise pressure drops could worsen bleeding whereas increases could push fluid into the body and cause swelling.
The researchers tested an early prototype of their system on two flights via NASA's Flight Opportunities Program in 2012. Airplanes nicknamed "Vomit Comets" flew up and down in parabolic arcs to simulate the reduced levels of gravity astronauts would feel on the moon or Mars or the microgravity they would experience on a deep-space flight, a virtue over such tests on the International Space Station that would only offer microgravity. Using silicone tubes filled with red sticky fluid to mimic blood vessels, experiments showed their system could stanch bleeding and suck away blood plumes from breaks in the tubes. The researchers detailed their findings in the December Aviation, Space and Environmental Medicine.
In February the scientists tried a variety of complex tests with more advanced prototypes of the AISS on a new series of reduced-gravity flights. For instance, they created a model of a kinked piece of bowel to see if they could use a scalpel and stapler with their system to fix that kind of surgical problem in space. Other experiments involved examining whether the shape of the dome affected how it filled and emptied in zero gravity; how well the domes stuck onto simulated skin; and how much the seals on the system might leak when instruments were taken in and out. They also sought to simulate veins’ low-pressure bleeding and arterial high-pressure bleeding to learn more about how blood moves and spreads in air and in fluid in weightlessness. "This a great potential idea that might provide a new approach to surgery in weightlessness," says trauma surgeon Andrew Kirkpatrick at Foothills Medical Centre in Calgary, who did not take part in this research.
One potential criticism of this system has to do with surface tension—the force that makes the surfaces of liquids contract. Prior studies suggested that in space blood’s surface tension it to mostly pool near wounds instead of floating. This means enclosing wounds could be unnecessary and would only increase the complexity of performing a surgical procedure. Still, "there are occasions when you have unexpected bleeding, and we'd like to try to manage those risks," Pantalos says.
"Surgery in space is going to be necessary, and this is a tool that might have some utility addressing that problem, but it's not proven yet whether this has some advantage over other approaches, such as minimally invasive laparoscopic surgery," Kirkpatrick says. "I think an actual prototype of the AISS should be created and tested in parabolic flight, and actual surgical procedures should be trialed. I do compliment the authors on their novel thinking and work, and encourage them to continue," he adds.
The researchers plan to test even more advanced prototypes of the AISS on future flights. "We've applied to fly on Virgin Galactic's SpaceShipTwo to test out what'd essentially be the final system," Pantalos says.