The first edition of the InnovaSpace Journal Club was dedicated to a prospective cohort study on jugular venous flow in astronauts aboard the ISS. From this study, the issue of jugular vein thrombus formation arose, which led to some fascinating discussion on how we could possibly manage and mitigate this novel risk to astronaut health. 
Therefore, I thought it appropriate to use the second edition of the InnovaSpace journal club to cover the issue of bleeding in space.

PAPER PRESENTED & DISCUSSED:

We used a 2019 literature review which evaluated different haemostatic techniques in remote environments and proposed a major haemorrhage protocol for a Mars mission.
The article itself stressed that while the estimated risk for major haemorrhage on a Mars mission was not very high, there were still many possible causes for a big bleed such as trauma and high dose radiation. Additionally, the changes to circulatory physiology observed in microgravity may mean astronauts are less able to cope with even small amounts of blood loss.
While the literature search itself left a lot to be desired as only 3 of the 27 papers were randomised controlled trials (RCTs), the results were interesting.

Firstly, we outlined how major haemorrhage is managed in a hospital on Earth and why, due to restrictions in mass and shelf-life of blood products, we would be unable to do the same thing on a mission to Mars.
We then looked at the haemostatic techniques used in remote environments. These included, Lyophilised plasma, Haemoglobin-based oxygen carriers (artificial blood) and Whole fresh blood. Each technique has its own advantages and disadvantages. The authors devised the ‘Floating blood bank’ protocol using Whole fresh blood directly supplied from a crew member in-situ.

The discussion afterwards featured doctors and medical students from Brazil, UK, Israel, Saudi Arabia and Romania and covered topics such as – How does space affect the coagulation cascade? How physiologically does space makes us more prone to Haemorrhagic shock? Should blood group be part of the selection criteria for crew? How should we weigh up the danger of physiological compromise from bleeding and a transfusion reaction? How do we weigh the threat of bleeding against clotting? Fortunately, there was a physician present with expertise in artificial blood which greatly enriched the discussion.
While this paper is obviously limited by the issue of sample size (which plagues all space health research) and the extrapolation of results from remote terrestrial environments to the extra-terrestrial environment, it still provides a foundational guide to how we could manage major haemorrhage in space. Further research could be utilised in the future to plug the gaps in our knowledge - how is the coagulation cascade effected by microgravity? How much blood volume does the human body need to lose in space before they go into shock? Are there alternative blood products not yet considered?

This article addresses the notion of buoyancy and why drinking beer in space (the ISS usually orbits in the thermosphere), or any carbonated drink for that matter, does not produce the known tingling sensation we can feel in our noses here on Earth.

So let’s first briefly consider what is buoyancy?
In simple terms, whenever an object is put into a fluid there are several forces that act upon it. The liquid exerts a force from the bottom upwards that tries to push that object up. Then there is the liquid force itself, let’s call it weight, that pushes an object downwards. However, because the liquid pressure increases the deeper you go down into the fluid, there will always be an upwards force bigger than the downward force.
This can be explained by looking at the formula for hydrostatic pressure:

In this formula, p is the density of the liquid, g is the gravitational force (9.81 m/s2) and h is the height of the fluid column measured from the surface. Keeping all the other parameters of the formula constant, the "h" at the bottom of a submerged object will be higher than the one at its top.
But we also have here another component: the "g". Well, there is practically no "g" in space, unless we artificially produce it. So, in this case, all the objects inserted or included into a fluid will just stay there.
Of course, there are many other factors that play a role here, for example the superficial tension of the fluids etc., however, for the sake of simplicity I am considering here only the buoyancy. So, nothing happens with the CO2 bubbles inside the fluid because they are no lighter than the fluid that surrounds them, perhaps looking something like in this photo:

This not mixing between the fluid and gases within creates a hard enough life for anyone who would like to enjoy a beer in space (hypothetically, at least as alcohol consumption is not permitted on the ISS), but let's also not forget the cabin temperature of roughly 20 degrees Celsius, which is way too high to enjoy an ice cold beer. If you want to cool it a bit forget leaving it outside too - just take a look at what the temperatures are "outside", unless of course you want to lick your beer like an ice-cream!

My name is Lucas, I am a doctor in the UK working in anaesthetics (or Anaesthesiology for any American readers) and intensive care medicine. I have had an interest in space medicine for over 10 years now, inspired by none other than Prof Thais Russomano who has mentored me over the years and still does. My Master’s dissertation (back in 2009) focused on CPR (cardiopulmonary resuscitation) methods in microgravity, with my continued research interest surrounding critical care in space. I am careful to say that I am a doctor with an interest in space medicine and physiology, as opposed to a ‘Space Doctor’ – as there are many individuals out there who have committed many more years than I have to this field and are vastly more experienced than I am! A club I aspire to join one day.

The idea of this blog, or series of blogs, is to look at some of the latest research in space physiology and space medicine, then consider how this will play out clinically. With a particular focus on critical care and potentially worst-case scenarios when in space (or microgravity environment). Something all doctors will have done in their careers; we are equipped with the skills to critically appraise papers and then ask if they are clinically relevant, or how will it change current practice.

​Over the last 60 (ish) years of human space flight, there is lots of evidence to show that there are many risks when the human body has prolonged exposure to microgravity, which can affect most body systems – eyes, brain, neuro-vestibular, psychological, heart, muscle, bone, kidneys, immune system, vasculature, clotting and even some that we haven’t fully figured out yet. But then what needs to be done is to tease out how clinically relevant are these from the research, how could that potentially play out if you were the doctor in space, then how to mitigate that risk and potentially treat it.