Space medicine: The science and logistics behind building a celestial armamentarium

If a bolt comes loose inside a spaceship cruising a few million miles from Earth, there is likely a solution in the binders full of schematics on board. But what happens if an astronaut develops a fever?

The science behind the rockets and sensors needed to complete a long-term space exploration mission is deep and expanding, but the science behind keeping explorers healthy is more uncertain.

“Research and knowledge regarding medicine and surgery in space is lacking,” according to Sandip Panesar, MD, MSc, Department of Neurosurgery, Stanford University, CA, in an interview with MDLinx. “It is impossible to anticipate every potential medical situation that may occur in space, but a medical contingency plan should include a crew member who is able to perform basic surgery and has advanced trauma and life support training.”

In a review published in the British Journal of Surgery, Dr. Panesar and Keyoumars Ashkan, MD, of King’s College, London, UK, recently summarized the current state of space medicine literature to further the understanding of the challenges that will likely be faced by space-travelling physicians in the future.

Space and the body

After breaching the Earth’s atmosphere and on exposure to microgravity, the body undergoes significant fluid redistribution. Both short and long-term compensatory changes occur regarding blood pressure and heart rate. Cardiovascular remodeling may also occur upon long-term exposure to extraterrestrial conditions.

“Other cardiac and vascular factors that remain to be studied in detail include the potential for cardiac dysrhythmias, and the effect of cosmic radiation on cardiac tissues and vasculature,” the authors wrote.

Since supportive bones and musculature have no gravitational forces to resist against, they will begin to atrophy. The lack of gravity appears to affect type 2 (slow twitch) muscle fibers more than type 1 (fast twitch), but onboard resistance training can mitigate these effects. Furthermore, astronauts may be at increased risk of pathological fracture due to bony atrophy.

Immunity challenges

A variety of factors combine to put the mission crew at greater risk for infection.

“Lymphocyte subtype composition is known to vary in space, relative to earth” Dr. Panesar said, “and cortisol levels may also increase as a stress reaction, which may adversely affect the immune system.”

Because the crew can’t go outside to catch some fresh air, the crowded, enclosed environment and recycled air may additionally increase susceptibility to infection.

“Microbes are also known to become more virulent in the space environment,” he added. This is thought to occur due to altered gene expression and protein regulation. Common pathogens, such as Salmonella and Pseudomonas, have been shown via animal experiments to become increasingly virulent relative to their pathogenicity on Earth.”

The trouble with drugs

Prevention and environmental control may be the best option for dealing with infections and other illnesses midflight. While the authors note that NASA-sponsored missions require candidates to undergo a variety of standardized and specialist vaccinations in addition to rigorous screening for tuberculosis, methicillin-resistant Staphylococcus aureus, and HIV, the pharmacokinetics and pharmacodynamics of drugs in space is not well understood.

“I can postulate that due to an altered cardiovascular system and fluid dynamics, the hepatic and renal excretion of various drugs may be altered when compared to the terrestrial pharmacodynamic profiles,” Dr. Panesar said.

The drug pipeline for space-specific medicines is not robust, so common antimicrobials, such as penicillin, cephalosporins, and aminoglycosides are likely to be part of the celestial armamentarium. Given that some antibiotics can be toxic on Earth, the patient’s hemodynamic profile is likely to be altered, and the space-mutated pathogen has an increased virulence, how does the onboard medical officer handle dosing strategies?

“There will be a significant amount of trial and error, likely involving empiric treatment of potential infections,” Dr. Panesar said. “Due to the exploratory nature of these missions, the participants may not have access to microbiological investigations such as cultures to specifically tailor treatment.”

Surgical suite

On a long mission, it is almost inevitable that open surgery will need to be performed—a daunting logistical challenge.

Surgical experiments have been conducted in simulated microgravity conditions, as well as on spacecraft. Restraint, easy access to materials, and environmental contamination are of the utmost importance.

“These considerations have led to the concept of a traumapod, which is an enclosed suite providing all necessary facilities and equipment for surgery in adverse environments,” the authors wrote in the review. “Proposed adaptation of this concept to space includes a dedicated medical module incorporated within the construction of the spacecraft.”

In microgravity, blood tends to pool and form domes that can fragment when touched by surgical equipment. In addition, organ evisceration has been reported in some experiments. While a hermetically sealed enclosure placed over the surgical site has been proposed to address these problems, unresolved obstacles include versatility for a variety of procedures, light refraction in gases or fluids, and fogging.

Presurgical anesthetization presents its own difficulties. To start, fluid redistribution in the body can lead to congestion of the vessels in the upper body, leading to edema of the tissues of the face, head, and neck. This can cause great difficulty with intubation or masks.

“The spacecraft is an enclosed environment,” Dr. Panesar said. “Using gases such as high-flow oxygen has the potential to lead to catastrophic fire due to its accumulation. Other anesthetic gases may also build up and adversely affect other crew members. At present, the use of anesthetic gases is contraindicated. The use of local anesthetic techniques has been proposed as an alternative.”

Cargo space is precious on long-term spaceflight, so any potential surgical suite onboard a spacecraft will have to function with less equipment.

“As surgical instrumentation is highly specialized and often unique to a subspecialty, it would be impossible to carry all the equipment necessary to treat every anticipated space pathology,” wrote Drs. Panesar and Ashkan. “A digital database of surgical tool templates for fabrication as needed would effectively solve the issue of limited stowage.”

The duties of a physician on a long-term spaceflight will be varied and are likely to be unprecedented. Dr. Panesar posits that the ideal candidate will have considerable experience performing similar duties under adverse circumstances, such as the battlefield.

“Nevertheless, space is still going to be very different from anything they will have encountered,” he added. “It is likely that a degree of trial and error is unavoidable.”