hey well welcome to another MedCram lecture today we're going to talk about
pulmonary embolism and specifically we're going to talk about the
epidemiology and also the risk factors and the next lectures we'll talk about
other things for instance the diagnosis and treatment first of all what is a
pulmonary embolism well to look at this we've got to look at the relationship
between the heart and the lungs as we know we've got the heart which pumps
blood to the lungs and also the left side which pumps blood to the rest of
the body and on each side we've got the lungs which sits on the left and the
right now of course we know that the venous system not only from the bottom
but also from the top drains into the right side of the heart and from there
from the right atrium it goes to the right ventricle and the right ventricle
pumps blood specifically to the lungs because of this any blood clot in any
vein is eventually going to end its way up if it breaks forth into the right
side now because of that the right side of the heart pumps this clot into the
pulmonary arteries and because the pulmonary artery gets smaller and
smaller and smaller and smaller that blood clot is going to get caught in the
lungs and get lodged and that's what's known as a pulmonary embolism
now it's because blood flow typically goes more to the lower part of the lung
than it does the upper part of the lung and that's a result of gravity more or
less because of this you're going to see more pulmonary embolisms in the lower
portion of the lungs and less in the upper of course it can happen anywhere
but just as a general rule since more blood flow goes to the lower portion of
the lungs you're going to tend to see more blood clots lodging in the lower
portion of the lungs now is there any predilection as to what side they tend
to go on now the answer is not really but it's possible for it to actually get
stuck in the middle where the pulmonary artery branches that's known as a saddle
embolus and that can be fatal obviously because of the large amount of blood
floo that gets disturbed at that type of pulmonary embolism okay so what is the
incidence of pulmonary embolism believe it or not it's about 600,000 people per
year get a pulmonary embolism and this results in anywhere between 50,000 and
200,000 deaths per year that's a lot of people and so I think this is an
important diagnosis to talk about okay now that you know what they are let's
talk a little bit about them in general first of all we miss them a lot
what do I mean by that we miss them a lot
they happen a lot in the emergency room and in the hospital and we fail to pick
them up because we don't realize this and how do we know that we miss them a
lot because of autopsies okay we see them on autopsies and we didn't even
think that the patient would have had them we also test for these a lot and
what happens is they're negative so we think that they're there and we test and
they don't turn out to be positive and in other cases we don't even think about
them and on autopsy we see pulmonary embolism what does that tell you tells
you that we're not doing a good job of picking these things up and it's
probably one of the most misdiagnosis in the hospital where do these things come
from well most pulmonary embolisms are from
deep venous thrombosis and most pulmonary embolisms from deep venous
thrombosis come from the lower extremities above the knee so they're in
the legs above the knee that's where we need to start looking for these things
so well what is the pathophysiology the pathophysiology specifically is is that
these blood clots form down in the legs because of a number of possible risk
factors they break off they go up the inferior vena cava to the right atrium
to the right ventricle and then they lodge themselves in the lungs now what
happens there when the blood cut gets lodged in the
pulmonary artery there is no more perfusion to that area of the lung and
so what you're getting there is ventilation without perfusion and that
is basically dead space and more forward is that the blood that should have gone
to that area that has to get diverted to other areas of the lung and then you get
an increased flow of blood to the other areas and so the major mechanism is VQ
mismatch if you have any questions about the mechanism of VQ mismatch please see
our hypoxia lectures and the mechanisms of hypoxemia now you also get increase
in resistance to blood flow especially on the right side specifically and that
can cause cardiac arrest in some situations you can actually get the
lungs to infarct about 10 percent of the time it's difficult because there's a
dual blood supply as many of you know the lungs have a dual blood supply
we know that the pulmonary artery goes to the lungs with deoxygenated blood
okay so deoxygenated blood goes to the lungs that way but also the aorta which
is coming off from the left side of the heart also sends branches over to the
lung and so it's difficult to infer the lung completely okay so let's talk about
risk factors what are the risk factors for pulmonary embolism now the reason
why this is important as we'll talk about later is that there is no test for
pulmonary embolism that you would order in another situation and accidentally
pick up a pulmonary embolism what do I mean by this I mean the only way you're
ever going to make a diagnosis of a pulmonary embolism is if you order a
very specific test looking for pulmonary embolism and what does that mean that
means if you're not thinking about pulmonary embolism you'll never really
make the diagnosis so it's very easy to miss it so what are the things that
should clue you in that this is a pulmonary embolism well it's risk
factors so what are some of the risk factors one it would be an orthopedic
procedure okay so what do I mean by that we're talking hip replacements knee
replacements or repair of fractures these sorts of procedures cause patients
to not only be laid up in bed but also the endothelial damage that occurs
during these surgeries and the fact that these patients probably haven't been
moving around very much in the preceding days two weeks before this procedure so
if somebody has an orthopedic procedure and comes down with symptoms of
tachycardia to get me as we'll talk about then you need to think about a
pulmonary embolism number two patients without prophylaxis what do I mean by
prophylaxis this is like DVT prophylaxis well the things that we're thinking
about in hospitalized patients would be bilateral lower extremity sequential
compression devices or anticoagulants things like heparin lovenox warfarin
things of that nature even things during surgery so these are all possibilities
what's another risk factor number three abdominal or pelvic surgery especially
if it's done for cancer so cancer or abdominal pelvic surgery could increase
the risk and does increase the risk number four obesity increases the risk
number five women greater than 30 years of age and they are on OCPs and they're
smokers this is a serious combination right here that you shouldn't forget
I've seen personally in the intensive care unit in fact in one month I saw two
women over the age of 30 on oral contraceptives who were smokers and they
had problems they had pulmonary embolism so bad that in fact they ended up on a
ventilator number six hypercoagulable state okay
what do I mean by this things for instance like protein C and s
deficiencies so you can have one or the other that's a possible risk factor
another possibility would be something like factor v leiden that's another type
of hypercoagulable state finally the last one would be pregnancy okay so
think about these things when we are trying to think whether or not a patient
may have a pulmonary embolism because these risk factors certainly could be
involved okay what about the symptoms what would be the symptoms or the
clinical findings well the first one is a high heart rate known as tachycardia
the first thing you'll notice is that that is very nonspecific number two is
just as bad and that's to keep Nia these things here are very nonspecific and can
be seen in a number of diseases like pneumonia like a myocardial infarction
for instance so you have to be specific and circumspect when you're looking at
these because these can fit into many different categories hemoptysis or
coughing up a blood especially if there is a lung infection that's impossible
clinical finding also signs of pulmonary hypertension so what are those types of
signs well you'd sometimes see elevated liver
function tests or you would see an increased in the sound of a p2 on
auscultation you might also see signs of right ventricular hypertrophy both on
palpation and also on the EKG so these are signs and symptoms of a pulmonary
embolism some of the clinical findings join us for the next lecture when we
start to talk about in terms of pulmonary embolism the diagnostic
modalities so how do we figure out whether or not this patient really does
have a pulmonary embolism it's gonna be an interesting discussion thanks