00:00
Let's talk for a moment about, "Septic shock"
and the phenomena of “Disseminated
Intravascular Coagulation” or “DIC.”
So, sepsis, is all by itself
a very pathologic state,
will lead to very high degree
of morbidity and mortality.
00:19
And septic shock is basically
a response to pathogens,
driven by the innate immune system
and is caused by an overproduction
of inflammatory cytokines.
00:31
These will have an effect on recruitment
of inflammation throughout the body,
the stickiness of various vascular beds
and will cause extreme vasodilation,
so, the patient goes into shock.
00:45
And clear-cut manifestation.
00:47
A predictable consequence of sepsis is, DIC or,
“Disseminated Intravascular Coagulation.”
If we think about it,
in the site of a local infection,
say, in your skin someplace,
you would want to activate,
many of the coagulation pathways,
to prevent pathogens, from causing
damage and causing bleeding.
01:13
So, in a localized environment,
the activation that will
lead to clotting makes sense.
01:21
But, if you have systemic activation,
when there's only infection in one spot,
then, you will get into a
significant degree of morbidity
and mortality driven by this, DIC phenomena.
01:33
So, let’s walk through, what's going on here.
01:36
On the upper part of this panel,
you see bacteria.
01:38
Bacteria are releasing,
“Pathogen-Associated Molecular Patterns,”
or “PAMPS.”
These stimulate cells of the immune system,
of the innate immune system, macrophages,
to produce cytokines.
01:51
You will also get, complement activation,
you will get a number of inflammatory
mediators, being released.
01:56
And again, if we keep it localized,
to just where the bacteria are,
that's a good thing, that's
an appropriate response.
02:04
But, if we get too high a
level, released systemically,
then we start getting into
issues related to activation
of all these pro-inflammatory pathways
and procoagulant pathways, everywhere,
and that's when we get DIC.
02:20
So, here we have our pro-inflammatory mediators,
that are being released into the bloodstream
and they, at a sufficiently high level will
act at a distance in other vascular beds.
02:30
One of the main effects besides,
activating other inflammatory cells,
is that, these pro-inflammatory mediators,
things like tumour necrosis factor,
interferon gamma, et cetera,
will activate endothelial
cells, in various vascular beds.
02:46
The endothelial cells, lining the vessels,
will lead to vasodilation and
increased vascular permeability.
02:54
Again, in a localized environment,
that's exactly what we want to happen,
however, if we do this systemically,
that vasodilation, is going to cause hypotension
and that increased permeability is
going to cause us to lose fluid,
in all tissues of the body leading to, edema.
03:11
So, that's one component of the
activation of endothelial cells.
03:15
But when the endothelial
cells are getting activated,
other things are happening.
03:19
So, one, they will make more tissue factor.
03:23
That's what they should do,
in an inflammatory setting,
you want to make more things that
are going to drive, pro-coagulation,
so, you make tissue factor,
which will, drive the
extrinsic coagulation cascade,
to make a thrombus.
03:35
We also, want to block the
anticoagulation pathways,
again, we want to drive
coagulation in a localized setting,
a good thing and systemic setting, not so good.
03:48
So, we're going to impair
the anticoagulation pathways.
03:53
Things like, thrombomodulin,
things like antithrombin III.
03:58
So we're going to impair
those, the production of those
and then we are also going to
have the activation the production
of plasminogen activator inhibitor.
04:11
Again, we want to make sure that,
in a localized environment,
we get the maximum prevention,
against bleeding, but by doing
this systemically we will engender,
the formation of clots, everywhere.
04:24
So, those are things that the
endothelial cells are making now,
because they've been activated by the cytokines.
04:30
As a consequence, we will not be
breaking down clots everywhere
and we will be making more clots everywhere.
04:39
So, we will get increased fibrin deposition.
04:44
We will get, in that fibrin deposition,
then the accumulation of platelets
and we have platelet fibrin
micro thrombi everywhere.
04:52
So, the systemic effects,
of monocyte and macrophage cytokines,
are that we will get, diffuse
endothelial activation and thrombosis.
05:01
We will get more blood clots forming everywhere.
05:05
Things that we haven't talked
about as part of sepsis, is that,
we will also have reduced
myocardial contractility,
that will contribute to hypotension.
05:14
In addition to what's going on,
because we have increased vascular permeability
and we have vasodilation.
05:22
So, all these effects are
going to contribute to sepsis,
but the activation of the coagulation cascade,
as we've talked about and the blockage
or the inhibition of the anticoagulation pathways,
will lead to disseminated
intravascular coagulation.
05:39
With thrombosis and hypotension,
you can imagine that you have multi-organ failure
and as indicated there, the
mortality even in the very best ICU’s
around the world is 50%.