Healing gunshot wounds in microgravity

Question

In my setting, kinetic firearms are the handheld weaponry of choice for most people, despite centuries of technological advancement (and stagnation, somewhat). These range from chemical-propelled guns to electromagnetic guns, each with their own advantages. In practice, except for specialized weapons, the receiving end of these firearms suffer similar amounts of damage to what one might expect from real-life guns.

In addition, a significant fraction of the human population across all inhabited star systems live in small space space stations or in spacecraft, where they often deal with low and zero gravity. There are many physiological issues that arise from these environments, but most of them have solutions or workarounds. Said solutions reflect a near-future level of technological sophistication, and include such things as lab-grown synthetic foods and nutritional/hormonal supplements, all of which I have figured out plausible explanations for. However...

Injuries do not heal well in microgravity, much less debilitating injuries, and as of now there don't seem to be any definitive real-life solution for this. But the more daring of these space-dwelling "spacers" often find themselves with such injuries, which include gunshot wounds from the previously mentioned firearms. Anything from a stray shotgun pellet to the back to a sniper round through the rib would not heal properly in microgravity without assistance, and left untreated could kill the victim, but artificial gravity sources such as centrifuges can sometimes be unavailable. After all, your ship's propulsion systems may have been damaged in the same fight that earned you a gunshot wound, leaving you stranded far form any centrifuge station. Built-in centrifuges and spin tethers can also be expensive to install on a ship, and most opt out of such features.

How, then, would spacers go about treating serious wounds during extended stays in microgravity? What sort of realistic technological solutions for this might one find in, say, a zero-g first aid kit?

Answer 1

Most of the research on this topic is very new so it's hard to say exactly why wounds heal slower in microgravity. Some seem to suggest that microgravity in general somehow leads to general health issues:

Experiments performed in real and simulated microgravity revealed alterations in fibroblast and endothelial cell function, changes in ECM production and dysregulation in apoptosis. Interestingly, in astronauts, deficient immune function, signs of chronic inflammation and insulin-resistance have been observed. These alterations, resembling some features of systemic diseases which impair wound healing on Earth, could affect the body’s response to injury and could represent a model to study defective healing mechanisms

and

Fibroblast behavior during wound healing is tightly regulated by mechanical forces at the site of injury and the ECM-membrane mechanoreceptors-cytoskeleton system plays a prominent role in cell signaling [Demontis et al., 2017] (Emphasis mine).

In my not-a-doctor-nor-a-biologist opinion, the slowness of wound healing seems to be a combination of the general health-malaise that humans suffer from during long-term exposure to microgravity and the mechanical effects of microgravity that slow down the movement and "restructuring" process of cells. I suspect that in a gravity environment, the process of tissue growth is aided by the fact that gravity "settles" the cells rebuilding the tissue lattice, and in microgravity these just float around aimlessly.

Setting aside the general unhealthy state of space-dwellers, solving the mechanical issues of wound healing could be as simple as applying vibration. Multiple studies have been done that suggest full-body or even topical application of vibration has positive effects on long-term or chronic wounds, and I could imagine that in a microgravity environment, properly applied vibrations to the patient could induce movement in and simulate pseudo-gravity for cells at a microscopic scale.

In a first-aid or field-care scenario where centrifuges or other gravity-equipped healing stations are unavailable, first aid kits could be equipped with topical vibration modules that get taped to the patients near their wounds or larger belts that get strapped around the whole patient and shake them ever so slightly.

All that aside,

I'm generally of the opinion that for any serious space-exploration and long-term space colonization, some prerequisite medical breakthroughs will need to be made. The classic one is cancer: it's simply so much easier and cheaper to cure cancer than it is to completely radiation shield everything when you are talking about human colonization that covers "star systems". Either eliminate cancer from the get-go (think nanobots in the blood that are constantly vigilant or genetically engineering humans to be less susceptible) or cancer needs to be reduced to something with the severity of the common cold today: maybe dangerous to old or otherwise already compromised people, but nothing that will cause you to miss more than a couple days of work before the drugs kick in and clear it up.

This is why I suggest healing gunshot wounds in space would be simple: Simply grab the single-use medical nanobot injector syringe from the first aid kit and apply it to the wound. If you don't have nanobots, then maybe you've simply genetically re-engineered the humans to be able to heal normally in microgravity.

Answer 2

1. Apply pressure.

Even here on Earth healing a serious injury is no small thing. People can "just heal" from scratches and minor wounds, but major injuries like deep cuts regularly require one consistent thing.

Pressure.

We strap people up and apply pressure to almost everything. Twisted ankles. Broken bones. Deep cuts. Those that don't require this benefit nonetheless from gravity and our atmosphere, which are all applying some form of pressure.

Consequently, it would be believable for people in microgravity to use pressure (even up to a pressure suit so simulate 1 atmosphere force against the body or more) to overcome some of the limitations of microgravity.

I am not suggesting that pressure is magically replacing gravity. Only that some of the problems can be overcome through pressure.

2. 3D Bio Printing

Skin wound healing is known to be impaired in space. As skin is the tissue mostly at risk to become injured during manned space missions, there is the need for a better understanding of the biological mechanisms behind the reduced wound healing capacity in space. In addition, for far-distant and long-term manned space missions like the exploration of Mars or other extraterrestrial human settlements, e.g., on the Moon, new effective treatment options for severe skin injuries have to be developed. However, these need to be compatible with the limitations concerning the availability of devices and materials present in space missions. Three-dimensional (3D) bioprinting (BP) might become a solution for both demands, as it allows the manufacturing of multicellular, complex and 3D tissue constructs, which can serve as models in basic research as well as transplantable skin grafts. ("Wound and Skin Healing in Space: The 3D Bioprinting Perspective, Mateo & Gelinsky, 2021"]

Humanity is working on biological 3D printing right now. It's in its infancy, but it's proof enough that one solution to the problem is to replace the damaged components, be they organs, muscles, cartilage, or pretty much anything else. It's plausible that once we can create skin grafts with 3D printing, we will eventually produce everything else.

Answer 3

Wound putty

Current skin grafting technology involves living cells taken from the patient and grown up in a dish. This can be applied as a sheet or as a slurry with binders / carriers.

Wound Grafts: https://www.ncbi.nlm.nih.gov/books/NBK564382/

Currently, the most commonly used skin substitute is a cultured epidermal autograft (CEA). A full-thickness skin biopsy from the patient is obtained, and the keratinocytes are then used to develop a graft by expanding the cells into a neoepidermis...

A newer therapy product requires a biopsy from the dermal-epidermal junction to produce autologous cells (keratinocytes, fibroblasts, melanocytes) that are delivered in a suspension. This suspension is then applied to the wound by spraying it on the wound.

Your world has off the shelf universal donor keratinocytes, fibroblasts and assorted cells which are suspended in a gooey caulk of inorganic carrier molecules, nutrients and clotting factors. The cells are engineered (aka "transformed") to be unfazed by microgravity and resistant to native inflammatory cells. A syringeful is warmed up and injected into the wound.

The living cells and clotting factors stop bleeding and congeal into a clot which within a few hours is crosslinked into a living scar. Wound putty is usually for smaller wounds. If there are not other good options some people use several doses for larger wounds (e.g. to replace a missing eye).

In some individuals the universal donor cells are overambitious and these scars can continue to grow. Occasionally an overgrown putty scar (or puttymark) might require surgical removal down the road. Backwoods types pare down puttymarks themselves or tie them off with thread.

Or let them grow and wear arsenic rings through them as a charm to ward off any other bullets. In addition to hopefully warding off bullets the arsenic retards growth of the scar.