My nerdy interest du jour is battlefield medicine, tactical combat casualty care and field medicine (the non-military side of emergency medicine, used in disaster relief). The concept of triage and how to tackle logistical hurdles such as how to carry or transport sensitive equipment and items that need special storage (like refrigeration or freezing) in sparse or hostile environments is fascinating! I just ordered Battlefield Angels: Saving Lives Under Enemy Fire From Valley Forge to Afghanistan on my Kindle and can’t wait to dive into it (just have to finish A Feast for Crows first…)
I started thinking about the topic because an article in bizjournal.com caught my eye: U.S. Army backs Vascular Solutions’ freeze-dried plasma push.
Freeze-dried… freeze-dried plasma. For transfusion. Woah. We can do that?
Plasma is the part of the blood that does not include red blood cells (erythrocytes). You can draw a tube of blood from someone, spin it in a centrifuge, and separate the different components of blood:
Plasma is useful for transfusions in the case of blood loss. Plasma contains water, clotting factors and other proteins, and in the case of traumatic injury and blood loss, these properties can help keep a patient’s blood volume at proper levels so that blood pressure is maintained and the right proteins are in sufficient supply. Patients in the field may need plasma, red blood cells or transfusions of other specific components. Transfusion medicine is a huge and independent field of study. And again: flippin’ fascinating.
According to the infallible source of knowledge that is Wikipedia, the military has been using dried plasma since 1918, which – woah – I did not know, but it makes a sense that a solution was found early on to the challenge of carrying around a heavy liquid that takes up space and is susceptible to degradation. Plasma is mostly water, so dried plasma + water = transfusable plasma that stayed fresh for up to four hours.1
But different situations – environment and available resources, for example – call for different solutions. And even as late as the 1990s military surgical teams have carried units of RBCs on ice, and blood bags for the collection of fresh whole blood from soldiers if plasma or platelets were needed.2
Another cool bit of information that I’ve come across: it’s possible to transfuse too much blood. If someone has an injury and is bleeding internally, it don’t do no good to keep giving ’em fluids; they’ll just leak it out into the area around the wound, which puts them in a more critical condition. You can also have dilutional coagulopathy (in which you dilute out the patient’s platelets and clotting factors – seen in platelet-depleted RBC transfusions – they can’t clot and so can’t stop bleeding), you can put various electrolytes out of balance, cause lung injury, have donor-recipient antibody incompatibilities, and that’s all assuming you’ve already matched your donors and screened out units that contain the common transfusion-transmitted viruses!
But back to field medicine – we can freeze-dry plasma. Woah. Science is cool.