Pulmonary Embolism Explained Clearly – Risk factors, Pathophysiology, DVT, Treatment


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