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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