So now we're going to talk
a little bit about Hemostasis.
Hemostasis is the balance between
bleeding and clotting in our blood. It's
a constant interaction between those two
activities that's ongoing all the time.
The only reason we have liquid blood is, because
when clots are formed, there's a very active process
to break them down. And the only time we,
the only reason we don't have constant bleeding
is because we can clot effectively. So there's
a constant interaction between these two
characteristics of Hemostasis.
Many activities can impair normal
Hemostasis, including things such as massive
trauma, which leads to massive bleeding,
or disease like leukemia, that can cause damage
to blood cells, particularly to platelets and
can cause bleeding, or drugs such as
anticoagulants, or even aspirin.
Absence of clotting factor such as
Hemophilia A, also causes massive
bleeding or causes major bleeding.
Anesthesia, per se, has
no positive or negative effects upon the body's
ability to form clots or stop bleeding,
to lyse clots in the presence of thrombus,
which is abnormal clotting. But
the anesthesiologist is expected to monitor these things
and make sure that we're on top of it, and we can adjust
the body's ability to respond to either
bleeding or clotting accordingly.
In cardiac and vascular surgery, very large
doses of the anticoagulant Heparin are given.
And this prevents clotting. And during the work
that's being done, either on the heart or on
the blood vessels, Heparin can cause profound bleeding,
if not managed properly. One of the other
problems with Heparin is, even when you remove
the Heparin, it can have damaged platelets,
which are vital for clotting, so that ongoing bleeding
can be a problem, even when you've reversed
Heparin. It's relatively rare, but it happens.
It's up to the anesthesiologist to give the Heparin,
monitor its effects, and reverse it at the appropriate
time, and to use the appropriate
doses of reversal drugs. Because unfortunately,
they're not clean drugs either, and they cause problems.
Anesthesia drugs themselves do not play
a role in increasing or decreasing bleeding,
but hemodynamic changes such as hypertension
can increase bleeding, and must
be managed by the anesthesiologist.
So this triangle shows you the dynamic
process that's constantly occurring in your
body between platelets, which are these little organelles
which are necessary for clotting, the vascular
system, which produces some of the proteins
that are necessary for clotting,
and the body's protein system,
coagulation protein system, that's also
necessary for clotting
and for lysis of clots.