Tjiang W, See KS Kris, Osel Diagnostics, Osel Group
Space exploration comes with many risks and challenges. But what if you become seriously ill or injured?
Abstract: Space medicine is defined as: “The practice of all aspects of preventative medicine including screening, health care delivery, and maintaining human performance in the extreme environment of space and preserving the long-term health of space travellers”.
Medical emergencies in space are quite rare. The risk of an astronaut developing a serious illness and needing intensive care is very small, but it is still around 1% to 2% per person per year. In fact, in the last 50-odd years of space travel, no astronaut has ever undergone a surgical procedure in orbit, but that doesn’t mean it will never happen. A core feature of operational space medicine entails the support and protection of human life and physiology using state of the art life support systems. Aerospace physicians support the health, safety, and well-being of pilots, aircrews, and astronauts.
How Space Affects Health
The risks are grouped into five categories related to the stresses they place on the space traveler: Gravity fields, isolation/confinement, hostile/closed environments, space radiation, and distance from Earth.
The most immediately noticeable effect is sensory disturbance involving the vestibular system. Overall, 60% to 80% of astronauts experience space adaptation syndrome within the first three days (e.g. nausea, pallor and vomiting).
The most visible early physiological change is the redistribution of body fluid from the lower to upper body, resulting from the elimination of the gravitational loading experienced on Earth, which could put pressure on your eyes causing vision problems. Compression cuffs worn on your thighs will help keep the blood in your lower extremities to counteract those vision changes.
Without gravity working on your body, your bones lose minerals, with density dropping at over 1% per month. By comparison, the rate of bone loss for elderly men and women on Earth is from 1% to 1.5% per year. Even after returning to Earth, your bone loss might not be corrected by rehabilitation, so you could be at greater risk of osteoporosis related fractures later in life.
In order to prevent bone density and muscle mass loss while in orbit, astronauts spend at least an hour and a half in the gym each day, where they use specialized weightlift simulation equipment such as the Advanced Resistive Exercise Device, as lifting regular weights in a weightless environment just isn’t effective. Good regular exercise has been shown to keep your heart healthy, your bones and muscles strong, your mind alert, and may help with your balance and coordination. Spaceflight also leads to significant sleep disruption as a result of gross alterations in light and dark cycles, illumination and crew workload.
Above Earth’s protective shielding, radiation exposure damages cellular DNA and may increase your cancer risk. It can damage your central nervous system, manifesting itself as altered cognitive function, reduced motor function, and behavioral changes. Space radiation can also cause radiation sickness that results in nausea, vomiting, anorexia, and fatigue. You could develop degenerative tissue diseases such as cataracts, cardiac, and circulatory diseases.
Medical standards for spaceflight
Medical standards for spaceflight played an important role. Standards are stricter for astronauts than for professional aviators. Exclusions are for conditions that; i) may cause acute incapacitation (e.g. coronary artery disease, renal stones, epilepsy), ii) may interact with the space environment or life support systems (e.g. bullous lung disease or asthma), iii) are incompatible with a long duration deep space mission (e.g. need to exclude stable chronic conditions requiring regular medication).
Anaesthesia in Space
Space medications are therefore limited to whatever can be injected or swallowed. Medications should be chemically stable, thermally robust, and have an adequate shelf life, while the radiation environment may lead to more rapid degradation of these medicines than on Earth. Powdered medications can provide the stability desired. Examples of medication in typical kits on board are: analgesics, antibiotics, anxiolytics, anti-emetics, antidepressants, hypnotics and benzodiazepines.
The closed environment of a spacecraft renders inhaled techniques problematic. Vapours could contaminate the cabin, affecting other crew members, while oxygen leakage in the cabin environment would increase the fire risk. Nevertheless general anaesthesia has been successfully administered using i.v. agents in a variety of animal models on orbit. Ketamine has been proposed by some as the preferred i.v. agent for sedation, induction and maintenance of anaesthesia. It has a wider therapeutic ratio when compared with other i.v. anaesthetic agents and has less profound effects on airway reflexes and respiratory depression than i.v. anaesthetic drugs of similar potency.
Some proposed regional techniques as a preferred method of delivering anaesthesia in the space, because it leaves the patient conscious with a reduced dependence additional physiological support and the equipment associated with general anaesthesia. However, regional techniques are not suitable for a number of surgical procedures and require significant skill and training.
Surgery in Space
Microgravity necessitates a secure system of restraint for both the patient and clinician and, because of the large number of weightless, non-sterile particles suspended in the cabin, consideration needs to be given to the means of containing the surgical field to prevent contamination of the wound.
When you think about how fluids behave in zero gravity, it’s not all that surprising that blood “misbehaved” in experiment: The blood bubbled up from the wound and globs began to spew upward and then stopped. The blood had stuck together, creating a wobbling dome over the wound. Sponges and suction have been shown to adequately prevent cabin contamination from bleeding, with the exception of arterial bleeds. A variety of techniques have been demonstrated in parabolic flight animal studies including laparoscopic surgery and percutaneous aspiration of intra-peritoneal fluid under sonographic guidance.
Cardiopulmonary Resuscitation in Space
Cardiopulmonary resuscitation is an emergency intervention used to maintain blood circulation and oxygenation in the event of acute loss of cardiac output. If required during spaceflight there are various methods of CPR, alternatively a mechanical device could be useful when considering the effects of deconditioning on the CPR operator. However, the complex supportive critical care generally required after a cardiac arrest is unlikely to be available or sustainable over any extended period in the space environment.
Re-entry and Landing Considerations
The medical concerns of re-entry relate to risk of: i) spacecraft depressurisation, ii) crash iii) fire, iv) trauma of a normal landing, v) post-landing survival, which may include risk of water ingress if landing in sea. Immediately post-landing astronauts may experience a generalised weakness, orthostatic intolerance and neurosensory disturbance, including pitch sensitivity which may affect an individual’s abilities to walk. Once able, astronauts undergo a prolonged period of physical re-conditioning to improve both musculoskeletal and cardiovascular systems.
So what if such an emergency occurs?
In the event that a medical emergency does transpire, astronauts are given a bit of training beyond First Aid basics: They can stitch up a wound, pull a tooth and give various types of injections. The most common medical problems that befall astronauts (motion sickness, burns, aches and pains) can be alleviated through these measures without issue.
There are currently some very real limitations on what medical professionals could do in space to save a dying patient. If an astronaut is aboard the ISS (International Space Station) and in the midst of a medical emergency, a docked Russian Soyuz capsule (a lifeboat of sorts) can have them back in Earth’s atmosphere within 24 hours.
“We can stabilize someone who has a dramatic injury, but we can’t sustain a patient for long”
As this brief overview indicates there is much that remains unknown in the field of space medicine. It is clear that the same exploration that takes us out into the endless frontier of space will demand that we also continue to look within and explore the limits of the human body in this the most austere of all extreme environments.
References
Abadie LJ, llyod CW, Shelhamer MJ. The Human Body in Space. Human Research Program. June 2018.
All That's Interesting. A Day In Space: Explore Life On The ISS With Samantha Cristoforetti. ATI. August 2015.
Greenberg R. Space Medicine: A New Frontier for Aspiring Physicians. Association of American Medical Colleges. 2018.
Hodkinson PD, Anderton RA, Posselt BN, Fong KJ. An overview of space medicine.British Journal of Anaesthesia. December 2017; (119): i143–i153.
Norman A. Can You Perform Surgery In Zero Gravity?. ATI. May 2016. http://allthatsinteresting.com/surgery-in-space
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