I’ve spoken at length (ad nauseam?) about fluid, the
importance of keeping patients hydrated, and the ways the disease process of
Ebola works against that by making you vomit and poop and sweat out a lot of
liquid. But there is (at least) one other reason why our patients need a lot of
water, which is probably less intuitive. It has to do with inflammation.
Think what happens when you stick your toe with a big thorn.
The toe gets red and warm; it swells up a little. What is happening, at a
microscopic level, is that your body is swinging into action to fight any
possible infection and to repair any possible damage. These things happen:
Blood vessels open up in the toe to ensure that lots of blood arrives at the
injury (since blood carries many of the factors and cells that are going to get
the job done). More than this, though, the walls of the capillaries actually
become more permeable, so plasma (the liquid in blood) and the factors it
contains can actually leak out into the tissue, bringing the immune infantry
into even closer contact with the insult. So the toe swells up (more blood;
more fluid leaking into the tissue) and gets warm (ditto).
The problem with massive systemic infections like Ebola (or
like sepsis – a disseminated, blood-stream borne infection) is that processes
that work well for a toe don’t always work well for your whole body. If you get
a SYSTEMIC inflammatory reaction, you have blood vessels opening up everywhere,
and blood vessel walls becoming more permeable everywhere. Which has
consequences: Your blood pressure drops (if all the “hoses” get bigger, but the
amount of blood doesn’t, the pressure goes down), which means that your organs
become less and less well perfused. In other words, they get to a point where
they are at risk of not getting enough blood (and the oxygen it contains, and
the cleansing of waste products it provides) to keep on functioning. And this
effect is even greater because, with all that “capillary leak,” the volume of
blood/fluid actually inside your blood vessels doesn’t remain constant – in
fact, it goes down. So – bigger hoses, less blood --> organs at risk of not
getting what they need.
As you can see, then – it isn’t just that Ebola patients
vomit and poop and sweat out a lot of fluid. It is that – plus the fact that
they lose fluid inside their bodies,
as well. Liquid that ordinarily would be inside their blood vessels has leaked
out into their lungs, their abdomen, their tissue in general. (Hence the puffy
appearance of many ICU patients – a person can actually have so much fluid in
their tissues that they appear bloated, while still not having enough fluid
actually inside their blood vessels.) All this while their blood vessels may be
much more open than usual, so the ability of their lowered blood volume to fill
the “hoses” is decreased yet further. Which opens the door to falling blood
pressure and organ failure – kidneys, intestines, liver that aren’t getting
what they need to survive, and thus begin to die.
In the States, we wouldn’t just put fluid back into the
blood vessels, as we do here. We’d do that – but we’d also use “pressors,”
drugs that actually tighten the blood vessels so that not so much fluid is
needed to fill them. And sometimes we might use “inotropes,” too – drugs that
make your heart beat more forcefully, which also increases blood pressure.
Here we just have fluid – lots and lots of fluid, by IV or by
mouth, if the person can swallow it. Trying to replace the fluid they’ve lost
through vomiting and diarrhea and sweating, but also the fluid they’ve leaked
out into their tissue; and trying to, if anything, increase the amount of fluid circulating in their blood vessels
from what it was before they were sick, since these vessels are likely to be
opened up by the disease process and thus in need of greater fluid volumes to
remain full.
You can see why I talk about it all the time!
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