Archives for January 2012

Because it’s Cold Out There

We rarely think about it. If we did, we’d probably lose our marbles.

But it’s true.

The universe doesn’t care.

We are born, we live for a little while, and eventually, we die. In the duration, we will have hopes and fears, passions, desires, successes and defeats, joy and pain. The whole gamut is out there. And as a rule, the inexorable pull of the world is downward — into darkness, into chaos. Scientists call it entropy. We just call it life.

But it means that at any given moment, if we want to be happy — comfortable, fulfilled, free from suffering — we have to be waging a constant battle. If we ever stop paddling, we start to sink.

There’s a certain point in your youth (maybe this is the moment that you become an adult) when you realize this battle is nobody’s but your own. When you’re a child, your parents agree to fight in your ranks until you can walk and talk and drive a car. But once you step out onto the world stage, the only one wearing your colors is you. As self-centered people, we find this hard to believe; we feel like we’re important players in the grand scheme. But the truth is that although everybody else feels the same way about themselves, they certainly don’t feel the same way about you.

Nobody cares about your problems like you do. Not even remotely close. They’re busy with their own battles, which are just as burdensome to them as yours to you. So we learn that if we want to solve our problems, change our circumstances, or just keep from backsliding in the constant undertow of life, we’re on our own. The tools we bring to the table are the only ones available, and our to-do list has only our name at the top. There is no oversight, unless we have strong religious views; no referee ensures that the dice land fair; and if the game proves too difficult, we don’t get to quit and try another.

Isn’t this horrible?

Of course it’s horrible. What could be more horrible than to be utterly alone in an uncaring universe?

So we try to build ties. From the little twirling piece of driftwood we’re clinging to, we throw out ropes to the other flotsam and jetsam. We bring them close and tie knots in the hope of building a raft that can stay afloat during the next storm. Maybe this way, we think, if I capsize, someone will pull me back in.

This is hard work, though. Because our own problems are bad enough, and to tie ourself to someone else means we’re taking on some of theirs, too. It means when they get hit, it’s our job to try and keep them afloat. That’s a lot of responsibility, and our plate was already full to begin with. (Everybody’s plate is full, no matter how big it may look from the outside.) So at the best, we only make a few really strong ties.

Oh, we might have a lot of weak ones. Folks we know, and who will occasionally drift by to exchange favors or chat. Maybe a group that we’ll cruise with for a while. But make no mistake: they might be floating alongside us, but they haven’t tied any knots in that rope. If you start to founder, the best you can hope for is a little sympathy as they sail on ahead, and maybe toss you a spare life preserver. It’s not their problem.

The ones who really throw in their lot with you — who say that in thick or thin, in sickness or health, they’ll be at your side, fighting to keep you afloat — they’re few and far between. Maybe a little family, one or two close friends. A significant other. That’s all.


What do you think happens when you get older?

If you have the good fortune to live to a very old age, then a lot of things will change. Life is not going to suddenly become easy; if anything, it will become harder. And where are those ties you’ve built?

Dead. Moved away. No longer capable of anything more than clinging to life.

The luckiest among us will make it to the very last pages of life with our partners-in-crime still at our side. The spouse of fifty years, the close and loving family, the lifelong friend. But for most of us, these lifelines are lost over the years, one by one. And eventually, we may have nobody. Nobody to fight for us, to love us, or even to note our passing.


The next time you transport the 80-year-old man with dementia, who never seems happy and complains about everything —

The next time you’re called to the home of the little old lady with toe pain, whose husband died recently after a lifetime spent together —

The next time you pick up the same homeless man from under the bridge, drunk once again —

Try to imagine what it would be like to be truly alone.

Nobody to lean on. Nobody to throw you a rope when you start to founder. Most of all, nobody who gives a damn you exist. Imagine what it would be like to know that you could walk into the sea tomorrow and nobody would even know you’d died — let alone that you’d lived.

We can’t be everything for these people. But one day, hopefully not soon, you might just find that you’ve become one of them. So do what you can, knowing that nobody else is likely to. Knowing that, even when it has little effect, the difference between having somebody to fire a few shots for you, and having nobody — can be all the difference in the world.

Understanding Shock VI: Fluid Resuscitation

So we know now that in any hemorrhagic shock, controlling the bleeding is step one, and restoring the supply of something resembling blood is step two. Should we also consider infusing some other fluids, even those that don’t help carry any oxygen?

Why would we even consider such a thing? It would make sense if “fluid” is what we’re missing, which is the case when shock is caused by something like dehydration. But in hemorrhage, we’re missing blood, not water. Still, there are a few reasons this might be worthwhile. Let’s discuss the “pro” arguments first, then come back around and talk about the “cons.”


The hydraulic argument

Fundamentally, the human vascular system is a hydraulic circuit.

In other words, it’s a giant circle of stretchy elastic tubes, like those long circus balloons. It’s all filled with fluid, which stretches out those tubes and pressurizes the whole system. Then a central pump pushes all the fluid in the system around in an endless loop.

One of the properties of such a system is that, without adequate internal pressure, it won’t work. It’s not that it works badly; it just fails altogether. And although pumping harder and faster can help elevate the pressure a little, and squeezing down on the tubes to make them smaller can help more, in the end if there’s not enough fluid in the system, nothing’s moving anywhere. If the heart isn’t filling with a certain amount of blood during diastole, it won’t push it forward during systole; it can’t pump out what it doesn’t take in.

So maybe there’s a certain logic for maintaining an adequate blood pressure, no matter what sort of fluid we’re actually circulating. Although pressure alone doesn’t carry oxygen, maintaining some pressure is certainly a prerequisite for carrying anything. To put it dryly, although BP isn’t everything, people with no BP are dead.

Moreover, some of the pathways in the shock cascade are, perhaps, initiated by low intravascular volume as much as by actual inadequate oxygen delivery. If we can keep the circulating volume pretty decent, maybe we can convince the body that all’s well — no need for a freak-out today.


The extravascular resuscitation argument

Flip back the calendar to the era of the Vietnam War, a landmark time in trauma care. Researchers like Dr. Tom Shires were experimenting on dogs.

They’d do things like drain from them a fixed volume of blood, then clamp off the bleeding and wait for a bit. Then they’d put back every drop of blood they’d removed. Most of the dogs died nonetheless, a phenomenon you and I now understand, since we’re totally experts in the self-sufficiency of the shock process.

But then they’d repeat the experiment. Only this time, rather than just giving the dogs back their blood, they’d also give them some crystalloid fluid. Just water with some stuff like electrolytes in it. This time, more of the dogs survived.

The theory explaining this goes something like so: where is most of the fluid in your body? We know that a high percentage of our bodyweight is water, but does that flow mostly in the blood? Anatomists talk about three different fluid “spaces”: the intravascular space (inside the vessels, where the blood circulates); the intracellular space (the interior of our actual cells); and the interstitial space (the “sea” of fluid permeating the tissue beds but outside the cells, bathing and nourishing them). Fluid moves between these spaces as needed, but at any given time, the majority of your body’s fluid is actually in the interstitial and intracellular (the extravascular) spaces — that is to say, not in the blood at all.

Shock causes increased permeability of the tissues and of the vascular tree, while simultaneously dropping intravascular (hydrostatic) pressure. So when the dogs entered shock, after a short while fluid began to “leak” from the interstitial and intracellular spaces back into the intravascular space. In essence, the dogs’ tissues were returning some of their retained fluid back into the bloodstream — and human tissues do this too. This shift actually increases the vascular volume, which is nice in a sense, and can be seen as a method of compensation: the body is tapping some of its reserve fluid to restore what was lost. However, it does leave the tissues dry. By infusing some saline along with the blood, Shires was helping his test subjects resuscitate both spaces. The intravascular space needed blood, but the extravascular spaces just needed fluid. (Of course, if we replace the blood, eventually the extravascular tissues will be rehydrated and the loaner fluid returned; but if we didn’t provide any extra fluid, that would once again leave the intravascular compartment a little light. Also, some of it — which leaked into neither the intravascular nor extravascular spaces, but the “third space,” areas such as the abdomen where it doesn’t belong — won’t be readily returned at all.)

Some combination of these two arguments became the foundation for a decades-long practice whereby hemorrhaging patients are given a certain amount of crystalloid (usually saline, or a modified form of saline like Lactated Ringer’s), often prior or in addition to giving blood products. In many cases this fluid is titrated to maintain a desired blood pressure, and this practice is still widespread today, especially in the prehospital world. In some cases, colloidal fluids (which contain large molecules such as proteins) are also used and have generally similar effects.

Key points:

  1. Bleeding control and restoring actual oxygen-carrying capacity are the main priorities in hemorrhagic shock, but there may also be value in non-blood fluid resuscitation.
  2. One argument for this is the maintenance of adequate blood pressure in order for the circulatory system to function.
  3. Another argument is the replenishment of the fluid lost from extravascular spaces.

Next episode we’ll discuss the dark side of crystalloid resuscitation.

Go to Part VII or back to Part V

Understanding Shock V: Blood Transfusion

So let’s say we’ve stopped the bleeding as best we can. Now what?

The patient is still low on blood, and we know about all the problems this will cause. So shouldn’t we try and give them some back?

Well, maybe.

It makes sense that someone who loses blood should get some blood replaced. And this is a very old concept. Once upon a time, we simply drew blood from one person and gave it to another — a process that was greatly improved when we learned how to screen and test blood for compatibility and disease. This method is still used in some settings, such as the military, which treats its entire force as a “walking blood bank.” If Pvt. Joe needs blood, they check the registries to find a match, then call up Pvt. James and have him swing by to donate a few bags.

In most other settings, however, whole blood transfusion has largely become a thing of the past. Instead, when blood is donated, it’s immediately reduced to its constituent parts. The red blood cells are pulled out and stored as packed red blood cells (PRBCs); the platelets are pulled out and stored as condensed platelet concentrate; and everything that’s left — the plasma itself, including electrolyte-rich water, clotting factors, immune factors, and other ingredients — is frozen and stored as fresh frozen plasma (FFP). One unit of blood (around a pint) yields one unit of each component. Since most patients only need one or two of these components, we can divvy them out as indicated, and the same blood supply can benefit up to three people.

So for years it’s been standard to transfuse traumatic shock patients red blood cells. As we know, the key problem of shock is inadequate oxygen delivery, and red blood cells are how we deliver oxygen. So drop in a few extra hemoglobin, perhaps top them off with a bit of fluid to keep things moving, and we should be set, right?

Maybe. But this leaves out a number of factors.

First of all, remember our prime directive. Stopping the bleeding is more important than topping off the tanks. How does our body control bleeding? Platelet aggregation and coagulation. And remember that platelets, the bricks of this process, are not reusable; if we have a lot of trauma, and we lose a lot of blood, we can easily run out of them. Does transfusing red blood cells alone provide any platelets? Nope.

So maybe we should throw in some platelets too. But wait — we know that to actually bind the platelets into a cohesive clot, we need a host of backup players, the numerous coagulation factors that live in the plasma. Does a platelet pack provide these? Nope. (Okay, platelets are usually stored in a small amount of plasma, so there’s a few, but not enough.) So maybe we should give the patient some plasma too (or even isolated concentrates of clotting factors to really supercharge the process).

The result of all this is the recent movement towards so-called 1:1:1 therapy, where trauma patients receive equal proportions of red blood cells, plasma, and platelets. In other words, they end up getting all the individual components of whole blood; we just don’t often have whole blood available, or we might give that. This is still an area of active research, and the exact ideal ratios are up for debate; the ratio of red blood cells to plasma is often either 1:1 or very close to it (1:2, 1:3, etc.), and platelets are usually given in somewhat lower quantities, but should not be neglected. The best ratio, as well as the actual quantity of blood to ultimately give, remains to be seen.

Logistics can stand in the way of some of these efforts. For instance, plasma is typically stored frozen (as FFP), and therefore needs to be thawed before use, a process that takes some time. Very large trauma centers may be able to keep a rotating supply of thawed plasma on hand for emergency use, but many facilities won’t be able to have plasma immediately available in this way. And although transfusing in the field seems tempting, the practical challenges of carrying blood products on an ambulance are daunting.

Furthermore, banked blood is not “as good” as the patient’s own blood no matter how it’s given. Even a 1:1:1 transfusion, properly typed, screened, and cross-matched, has real risks of transmitting infection or causing an adverse reaction, carries less oxygen than fresh blood, has reduced hemoglobin pliability (the little disks “stiffen,” becoming less able to squeeze down capillaries to reach the hungry cells), and reduced numbers of labile clotting factors (particularly V and VII). It carries less 2,3-DPG, its pH is lower, and due to the anticoagulants and preservatives added for storage, it’s literally larger and more dilute than the whole blood it started as. Since transfusions are generally not our problem in the field, the applicable moral here is simply that “top ’em up” is not a simple or easy answer to shock, and the only intervention that truly keeps the patient out of trouble is to stop the bleeding!

From the Trauma Professional’s Blog at


In brief:

  1. Blood transfusion is an important step in treating traumatic shock, secondary only to controlling the source of hemorrhage.
  2. Modern “component” blood banking allows for the administration of almost any ratio of red blood cells, plasma, and platelets.
  3. Transfusing primarily red blood cells is the traditional approach, but a movement has recently developed toward more balanced ratios.

Next time: the legacy of crystalloids.

Go to Part VI or back to Part IV