Pulmonary Embolus Index of Suspicion and Initial Steps Towards Diagnosis...

Discussion in 'Emergency Medicine' started by divinemsm, Jul 26, 2006.

  1. divinemsm

    divinemsm Pseudo Intellectual

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    V/Q Lung Scan vs. Chest X-Ray and ABGs.....does increased or decreased suspicion dictate one route over the other..? ( so asks the MS 4 ....) thanks! :)
     
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  3. GeneralVeers

    GeneralVeers Globus Hystericus
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    Always get a CXR on any patient with tachypnea, or hypoxia. This may lead to an alternative diagnosis like CHF or pneumonia which can explain the symptoms.

    V/Q scan is rarely used anymore, as COPD, and other chronic disorders can lead to false positives or "intermediate probability" scans.

    CT Pulmonary Angiography is the most commonly used method now. It's fast and easy to get. If I have an intermediate to high suspician of PE this is the first thing I get after CXR.

    ABG, D-dimer have some utility, but are not specific enough to rule-in PE. A negative D-dimer does have high negative predictive value, however.
     
  4. divinemsm

    divinemsm Pseudo Intellectual

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    Thank You ! :D
     
  5. MushieCookie

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    Does Spiral CT play a role in this anymore?
     
  6. BKN

    BKN Senior Member

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    I believe spiral CT = CTPA
     
  7. dlung

    dlung Postprelim intern oranges

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    I ordered several V/Q scans last year because at a certain federally-funded medical center, because of certain staffing issues, it was a lot faster by a certain amount of time (hours to days) to get a V/Q scan than any sort of CT.
     
  8. docB

    docB Chronically painful
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    I wind up doing VQ scans about once or twice a week due to pregnancy, contrast alergies or equipment failures. CT is better.
     
  9. southerndoc

    southerndoc life is good
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    Here in the big Ivy tower, V/Q scans were still the standard of care until 6 months ago. Amazing how things take so long to change where the pioneering diagnostic data was done. The "powers that be" were resistant to change because it was "unproven." HA!
     
  10. waterski232002

    waterski232002 Senior Member

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    Chest CT with contrast is the best test for anyone you have a reasonable suspicion for PE in (if they have any risk factors, story sounds good, or physical exam finding/vitals consistent with).

    D-dimer is really only useful in ruling out patients who are very low risk (24 yo F w/ no medical problems who c/o sharp CP and feels anxious, no risk factors, all vitals and PE normal).

    Probably anxiety, but to make yourself feel better and her feel better, you get a d-dimer to rule it out. She has no reason to have an elevated d-dimer.

    Don't even think about ordering a d-dimer if the patient has multiple medical problems, big risk factors, or any inflammatory diseases.... just scan.
     
  11. southerndoc

    southerndoc life is good
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    There is research to suggest using a negative d-dimer AND a negative CT to exclude PE. It provides more security since CT has been reported to miss from 2-10% of PE's (radiologist and CT-generation dependent).
     
  12. waterski232002

    waterski232002 Senior Member

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    That makes no sense.... d-dimer's are incredibly non-specific and can be elevated for a plethora of reasons. Most patients who you suspect PE have multiple medical problems so d-dimer's are of little-to-no value (IT IS GOING TO BE ELEVATED, but doesn't mean crap about acute PE pretest probability) D-dimer only helps when patients do NOT have complicating factors which could lead to false positives.

    With a negative CT you're now telling me that you can't rule out PE??? Then after a positive D-dimer there would be no point to CT someone's chest b/c either way you still can't exclude PE so you'll have to treat them all regardless of the CT result. :rolleyes:
     
  13. NinerNiner999

    NinerNiner999 Senior Member

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    Also, if there is any significant delay in obtaining the needed studies, and the patient has a high probability of PE (swollen leg, O2sat 89, tachypnea, tachycardia, etc) go ahead and treat before your scan...
     
  14. waterski232002

    waterski232002 Senior Member

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    I would argue, that these 2-10% of PE's "missed" by CT are insignificant anyways. If your patient has clinical signs consistent with PE (tachycardia, tachypnea, hypoxia, and/or significant SOB/CP), then this person does NOT have a tiny PE that will be missed by CT. So if the CT is negative, you better look elsewhere for your cause of distress. PE is NOT the major contributing factor in these cases.
     
  15. BKN

    BKN Senior Member

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    Try this systematic review: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16052017&query_hl=1&itool=pubmed_docsum

    It's the best that I've seen. Most interesting fact I got it that is not emphasized in the paper is that All of the D-Dimer studies which show ELISA superior to the other method were done in a single lab. No one else could reproduce it. Seems like ELISA should be treated the same as other d-dimers. They make diagnostic recs in the paper for low, medium and high probability cases, but you cann make your decisions as below.

    In using the likelihood ratios, set your prior odds at about .1 for low (probability 10%), 1 for medium (50% prob), and 4 for high (80% prob). Then multiply your prior odds by the likelihood ratio for the result you got. You obtain the posterior odds. Then backconvert to posterior probablility with the formula prob = odds/(odds + 1). If you get a probability less than 2%, I'd start looking for something else. But you can set the cutoff wherever you are comfortable. If you don't get high enough to treat or low enough to discard, do another test.

    BKN
     
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  17. Seaglass

    Seaglass Quantum Member

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    "If your patient has clinical signs consistent with PE (tachycardia, tachypnea, hypoxia, and/or significant SOB/CP), then this person does NOT have a tiny PE that will be missed by CT. "


    I think this is frankly untrue, or at least not something to rely on. PIOPED II also showed that arterial phase only CTPA is not so hot for detecting PE. It is important to find those small peripheral PEs because the next one might be the saddle embolus that kills you!
     
  18. southerndoc

    southerndoc life is good
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    Remember, it is not the PE that the patient currently has that is usually the killer. It's the one looming. Of course this doesn't apply if the patient has a large saddle embolus. However, if they are showering small PE's, duplex ultrasounds of the lower extremities can still miss deep venous thromboses in the pelvic veins.

    I refer you to this article regarding d-dimer utility in negative CT's: Perrier. NEJM, 352(17):1760-1768.

    As with all things, whatever the research suggests doesn't mean you absolutely must incorporate it into your practice. I know of several hospitals who do incorporate this into their practice. We personally do not for CT imaging, but do for V/Q scanning (since most are read as low prob and not as "negative" or "normal" by our radiologists).
     
  19. beyond all hope

    beyond all hope Senior Member

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    Relying on a negative D-dimer to r/o PE in the ED is a little ridiculous if you have a low clinical suspicion (yeah, this lady's got pleuritic chest pain and she's on BCPs but vitals normal and EKG normal. Could she have a PE?).

    However, if you have a very high clinical suspicion, treat and admit for further testing - V/Q vs alternate diagnostics for other dx. Most people you have this clinical suspicion for meet admission criteria anyway (tachycardia, tachypnea, no other source).
     
  20. southerndoc

    southerndoc life is good
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    Actually a negative d-dimer is useful if you have low clinical suspicion. If the score is <2 and they have a negative d-dimer, I believe the likelihood of them having a PE is <0.5% if I remember correctly. (It's been 2 years since I read the literature.)
     
  21. Seaglass

    Seaglass Quantum Member

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    That's how I remember it.
     
  22. waterski232002

    waterski232002 Senior Member

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    It is the best test we have, and if your clinical suspicion is high and patient in distress, the patient should be anticoagulated before CT anyways.

    The point being, if your patient looks this ill and there is a diagnostically adequate negative CTPA... yes, maybe it missed a very tiny PE, but a tiny PE should not cause your patient to decompensate acutely... so it's not the cause for your patient's instability in the ER. If they code, you probably missed something.

    That has nothing to do with determining long term risk for PE, or need for anticoatulation despite a negative CT (accounting for false negatives). I don't know about you, but in the ER, I am more concerned about preventing my patient from decompensating acutely, than determining their need for anticoagulation on an outpatient basis (I didn't go into medicine for a reason).... that can be done at discharge when the patient is stable and feeling well. Keep them on their heparin gtt, and keep searching for causes.

    We recently had a 28 yo patient in our ER who came in with tachycardia, tachypnea, and thigh pain after riding his bike. His thigh looked a little erythematous and warm, and we suspected DVT w/ PE. He had a negative CTPA, after the study came back negative, cardiac enzymes were sent, and his CPK's came back at 1500. Rhabdo was suspected next, then his diff came back with 27% bands and urine myoglobin was negative as the patient was started on BiPAP. X-rays of the femur showed no SC air. Plastics was consulted, and his leg wound began blistering open 3 hrs after triage... within 4 hrs of presentation he was coded and died. We could have easily just said, "well the CT is negative but this sounds like PE" without looking deeper. Nec Fasc is a bitch....
     
  23. southerndoc

    southerndoc life is good
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    I look out for what's best for the patient, and that includes long-term anticoagulation when discharged from the ED. However, an unstable patient such as the one presented is unlikely to even be a consideration for discharge, even if the initial workup is negative.

    No offense, but this was not a clear cut PE/DVT. I doubt anyone on this board would have argued heparinizing this patient without a CT result. Without having seen the patient, my suspicion from what you describe is low for PE. However, hindsight is always 20/20, and it is more difficult to weed through the information presented in real time than it is to look in retrospect.

    Interesting CPK... 1500. Mine was 10 times that when I had rhabdo. :)
     
  24. Seaglass

    Seaglass Quantum Member

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    Actually sounds a lot like the cases of Community aquired MRSA pneumonia that have been described.
     
  25. 12R34Y

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    I agree. Was thinking the same thing. Usually nec fasc in an extremity lives quite a while (24-48 hours) in the ICU etc... and at least make it to surgery for debridement. Wonder why he would have a pure respiratory component from thigh infection?

    the community acquired MRSA pneumonia sounds like it kills people very very quickly.

    later
     
  26. BKN

    BKN Senior Member

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    Actually, nec fasc frequently kills very quickly.
     
  27. Seaglass

    Seaglass Quantum Member

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    after you find it!
     
  28. waterski232002

    waterski232002 Senior Member

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    The Autopsy report stated nec fasc (Group A Strep was isolated).... the pulmonary component was likely a rapid progression from local infection --> sepsis --> ARDS --> Respiratory Failure
     
  29. waterski232002

    waterski232002 Senior Member

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    I was referring to discharge from the hospital after admission. Obviously a patient showing distress from a large PE or another respiratory complaint equivalent to it would never be discharged directly from the ER.



    I agree. Re-read my posts... I never said it was a clear cut PE/DVT. I said we suspected it. The whole point was to keep a wide differential.
     

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