Pulmonary Embolus First Step in Diagnosis...

[divinemsm]

....arterial blood gases and chest x-ray OR V/Q Lung scan?...usmle world says the former, kaplan says the latter.....thanks !

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[sophiejane]

....arterial blood gases and chest x-ray OR V/Q Lung scan?...usmle world says the former, kaplan says the latter.....thanks !

I think it depends on your level of clinical suspicion. If it is high (all the typical signs, risk factors) then I think you start with V/Q. If that is neg, you can pretty much rule out a PE. If the sx are more vague, I think you can start with CXR and ABGs.

Does that sound right?

You might ask this in the EM forum. I asked a Q there the other day and got some great responses from actual docs and residents...unlike our lowly student forum.

 

[ucbdancn00]

....arterial blood gases and chest x-ray OR V/Q Lung scan?...usmle world says the former, kaplan says the latter.....thanks !

if i'm not mistaken

intermediate probability--> v/q scan

low probability---> ABG/Cxray

the problem with the Cxray is that it's nml most of the time so it doesn't really help you out. An ABG may help to establish the presence of an increased A-a gradient, but again is non-specific for PE (other things that increase A-a gradient--> shunt, diffusion barrier problems)

If the clinical scenario is pretty indicative of a PE, then V/Q is your best bet.......of course, if anti-coagulation is in the answer choices, it'd probably be better to go with that as the "next step".

If you're not sure what's the diagnosis is then it's better to start out with a Cxray (ie. help r/o a Pneumothorax), and ABG

hope this helps and good luck

ucb

 

[ucbdancn00]

I think it depends on your level of clinical suspicion. If it is high (all the typical signs, risk factors) then I think you start with V/Q. If that is neg, you can pretty much rule out a PE. If the sx are more vague, I think you can start with CXR and ABGs.

Does that sound right?

You might ask this in the EM forum. I asked a Q there the other day and got some great responses from actual docs and residents...unlike our lowly student forum.

damn sophie...

all done with the test and still at it....now that's a trooper

ucb

 

[divinemsm]

....you guys are the bomb ! I really appreciate your prompt replies..now I can move on to reviewing the rest of the 46 question block....thanks so much!

m.

 

[RastaMan]

I could be wrong but from what I've seen ABG, CXR is usually done first because its quick and helps rule out CHF, etc (or at least make it less likely if there are no infiltrates on CXR). Then, managment depends on the probability of PE:
1) low probability patient --> get d-dimer --> if negative, send home, if positive get V/Q scan or helical CT
2) High probability --> initiate heparin/warfarin --> then, do V/Q scan or helical CT (don't want to waste time on testing while a PE is more than likely eating away at good lung)
3) intermendiate probability --> first V/Q scan or helical CT --> then turf home or start treatment based on results
4) massive PE (hypotension and in general unstable) --> maybe thrombolytics

Someone can correct me if I'm wrong. Hope this helps

 

[sophiejane]

damn sophie...

all done with the test and still at it....now that's a trooper

ucb

no, not done just yet...I have the COMLEX tomorrow. this is called trying to keep my sanity until I can pass out in bed. better than studying.

 

[ucbdancn00]

no, not done just yet...I have the COMLEX tomorrow. this is called trying to keep my sanity until I can pass out in bed. better than studying.

word...

my brain is starting to melt inside my head..

ucb

 

[rads0518]

word...

my brain is starting to melt inside my head..

ucb

I had a question on Step 2 where all signs pointed to PE, but the question asked next step? ECG and V/Q were both on the list of next options, the others were obviously wrong. It would seem that V/Q is the obvious answer for PE. However, as we never want to miss an MI, might ECG be the correct answer. It seems that anytime a pt. had chest pain during my rotations, ECG was the first test run. This was one that I mulled for a while on the exam, ended up choosing ECG. Any thoughts on this?

 

[ucbdancn00]

I had a question on Step 2 where all signs pointed to PE, but the question asked next step? ECG and V/Q were both on the list of next options, the others were obviously wrong. It would seem that V/Q is the obvious answer for PE. However, as we never want to miss an MI, might ECG be the correct answer. It seems that anytime a pt. had chest pain during my rotations, ECG was the first test run. This was one that I mulled for a while on the exam, ended up choosing ECG. Any thoughts on this?

well...

while an ECG is an important test in the scheme of an MI workup, it isn't as useful here. I mean, granted you're likely to be able to r/o an MI, but in the setting of a PE--> sinus tachy is the most common finding; rarely you get the S1Q3T3 pattern (although it is more specific for PE, but not sensitive). In this context it's not going to be as useful in making the diagnosis...V/Q scan is much more useful esp in the setting of high/intermediate probabilities

i def know where you're coming from with regards to your rotations, but it's hard to translate everything from there into the exam b/c several hospitals will just run a whole gamete of tests...

hopefully this helps clarify things...

congrats on finishing, i take the beast tomorrow..

ucb

 

[4424]

here's a ? from qbook.
sudden onset of palpitations and SOB 5days post op knee replacement surgery. PR 100/mon and regular. O2 sat 90%. ECG shows sinus tachy. CXR normal. what is next?
1- ABG
2- Doppler duplex of LE
3- VQ scan
4- give oxygen
5- start IV heparin

the answer was 1- ABG. i thought it was fairly safe to proceed with the VQ at that point but i guess not

 

[DOapplicant]

it think if you're suspecting PE:

1) cxr (to r/o other eti in your ddx) and abg (to confirm PE findings of hypox and hypocarbia/inc pH)

2) if cxr neg and abg pos - start hep and then do confirmatory test (eg v/q).


if your suspecting massive PE (reg sx + new RBBB, JVD, MS change) s/p surgery- i think straight to hep.

 

[4424]

it think if you're suspecting PE:

1) cxr (to r/o other eti in your ddx) and abg (to confirm PE findings of hypox and hypocarbia/inc pH)

2) if cxr neg and abg pos - start hep and then do confirmatory test (eg v/q).


if your suspecting massive PE (reg sx + new RBBB, JVD, MS change) s/p surgery- i think straight to hep.

that makes sense. thanks

 

[Pox in a box]

here's a ? from qbook.
sudden onset of palpitations and SOB 5days post op knee replacement surgery. PR 100/mon and regular. O2 sat 90%. ECG shows sinus tachy. CXR normal. what is next?
1- ABG
2- Doppler duplex of LE
3- VQ scan
4- give oxygen
5- start IV heparin

the answer was 1- ABG. i thought it was fairly safe to proceed with the VQ at that point but i guess not

ABG is quick and can r/o panic attack or hyperventilation...benign things fast. However, a lot of centers have V/Q scans and that sounds like a classic PE (especially in association with tachycardia POD #5 s/p knee replacement).

 

[lsu1000]

UW is very contradictive on this. One explanation says V/Q is "usually" the first test to workup suspected PE.

However, in another more in depth explanation they say that the differential is very broad including pneumonia, CHF, pneumothorax, etc...so you should start with CXR abd ABG.


If the baseline CXR is abnormal(ie emphysema, fibrosis), you should perform spiral CT to check for larger clots.

If the baseline CXR is normal(the classic case) choose V/Q scan.

If V/Q is inconclusive(not negative but inconclusive), choose venous ultrasound of of lower extremities.


So recapping....the classic case that we will see on Step II....
1. CXR/ABG(most likely will be normal or noncontributory)
2. V/Q!!!

also..
D-dimers are non specific for PE, so they are not the "next best"

 

[Idiopathic]

UW is very contradictive on this. One explanation says V/Q is "usually" the first test to workup suspected PE.

However, in another more in depth explanation they say that the differential is very broad including pneumonia, CHF, pneumothorax, etc...so you should start with CXR abd ABG.


If the baseline CXR is abnormal(ie emphysema, fibrosis), you should perform spiral CT to check for larger clots.

If the baseline CXR is normal(the classic case) choose V/Q scan.

If V/Q is inconclusive(not negative but inconclusive), choose venous ultrasound of of lower extremities.


So recapping....the classic case that we will see on Step II....
1. CXR/ABG(most likely will be normal or noncontributory)
2. V/Q!!!

also..
D-dimers are non specific for PE, so they are not the "next best"

How many V/Q scans have you guys seen or seen ordered? Ive never seen one, but Ive seen lots of spiral CT's.

Im just saying. Its fun to not think in board terms anymore.

If you even say 'PE' in the hospital, three of your patients will be in the scanner so quick you wont know what happened.

 

[46&2]

Based on my little experience, patients with a decent probablity of a PE got wheeled down for CT PE protocol stat. I guess you're supposed to start anticoagulation immediately, but some patients (e.g. those with intracranial hemorrhage) have concerning contraindications to heparin, and if the PE isn't immediately fatal hopefully 30-60 minutes won't make a difference. If you don't get ABG immediately in real life, though, you'd look silly. You probably don't want to wait for the CXR though, since it's also time consuming (getting it + reading it) with low sensitivity. It may rule out/in some stuff, but it doesn't rule out the PE.

Incidentally, once saw a patient in the ED who was satting in the high 90s, normal HR, BP, RR. Only problem was subjective dyspnea. CXR showed a one-sided pleural effusion (Hampton's Hump?) of unknown eitology (no major past medical history). Internal med attending astutely ordered D-dimer which was high and patient did indeed have a PE according to CT angio.

From: Annals of Emergency Medicine
Volume 41 • Number 2 • February 2003

Clinical policy: Critical issues in the evaluation and management of adult patients presenting with suspected pulmonary embolism

"Level A recommendations
In patients with a low-to-moderate pretest probability of PE, a normal perfusion scan reliably excludes clinically significant PE.

Level B recommendations
In patients with a low-to-moderate pretest probability of PE and a non-diagnostic V/Q scan, use 1 of the following tests instead of pulmonary arteriogram to exclude clinically significant PE:

A negative quantitative D-dimer assay (turbidimetric or ELISA).
A negative whole blood cell qualitative D-dimer assay in conjunction with a Wells' score of 4 or less.
A negative single bilateral venous ultrasonographic scan for low-probability patients.
A negative serial
*Serial venous ultrasonography refers to scheduling a patient for follow-up examination in the ED within 3 to 7 days or referring to a primary care physician for follow-up.
bilateral venous ultrasonographic scan for moderate-probability patients."


"Patient management recommendations: can spiral CT replace V/Q scanning in the diagnostic evaluation of PE?
Level A recommendations
None specified.

Level B recommendations
Thin collimation spiral CT scan of the thorax with 1- to 2-mm image reconstruction may be used as an alternative to V/Q scan during the diagnostic evaluation of patients with suspected PE.

Level C recommendations
Spiral CT scan of the thorax with delayed CT venography may be used for increased detection of patients with significant thromboembolic disease."