okay 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
in the next lectures we'll talk about other things for instance the diagnosis
and treatment but let's talk about pulmonary embolism its epidemiology risk
factors things of that nature 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 in 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 typically 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
flow that gets disturbed and 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 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 ortho pivec 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 give 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 thirty
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
thirty 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 will 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 two Kip 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 increase 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 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
you