When to begin anticoagulation, when to get imaging?

[AbuSimpson]

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Just ran into a UW question about DVT that confused me.

Woman with clinical signs of DVT comes into the ER - UW says you get imaging (venous doppler) first, and then anticoagulate...

However, 70+% of people got this question wrong, so I assume it's not that obvious...Do you only begin "empiric" heparin before imaging for suspected PE? The answer explanation doesn't really make a good distinction.

AS

After reading this, it may seem straightforward to not give a drug before you know what you're treating. But you give prophylactic heparin to the majority of inpatients, so in a patient who has Homan's sign, on OCPs and has clinical features of DVT, why not get the heparin drip going?

 

[footcramp]

if there is a high suspicion for PE then you anticoag, same if patient is unstable with high suspicion. although i would still rule out MI and other things quickly with an EKG and CXR, perhaps ABG. if you're not sure if it's PE or other things, then for sure you do EKG/CXR/ABG first.

but if it's just a DVT, without suspicion for PE, then it's urgent but not an emergency. therefore the risk of anticoagulation outweighs the empiric benefits. thus a noninvasive DVT scan, which can be done fairly quickly, is a good initial step.

to answer your last question, the route and dose of prophylactic heparin is safer than what you would use to treat a dvt. usually 5000u subq for prophy, 5000-10000u IV with hourly drip for treatment...

 

[angel80]

In reality, in the hospital where I work, venous dopplers and CT scan for PE protocol can be done very quickly in the ER, so by the time you go down to admit the patient, they've already been imaged and you already have a definative diagnosis. I start anticoagulation when I admit them.

 

[Samoa]

I think that Qbook notes that many urban ERs have CT scanners within the department, but that for USMLE purposes you should assume you are at Podunk General (not in those exact words, of course).

Here's the difference: in PE, you're treating something that has a significant and imminent risk of death, as opposed to the theoretical risk of bleeding from anticoagulation. In DVT, you don't fear the clot itself, but rather the risk of embolization and subsequent PE. That risk is smaller, and needs to be weighed against the significant risks involved in anticoagulation. So the diagnostic test takes precedence over the therapy, because you want to be sure you're treating what you think you're treating.

 

[Major0909]

so what about for PE? Assuming a combo of the following are each listed as answer choices what's the recommended order if you go by the book?

ABGs
V/Q vs CT
Anti-coagulation

I'm assuming get the diagnosis first for board purposes...

 

[footcramp]

stable then ABG before V/Q or CT. easy and quick. CT is preferred over V/Q but not clear for usmle purposes...
unstable then depends on how big the clot is and where it is

 

[Idiopathic]

PE is the worst clinical scenario in the world to test over, because in the real world, you will be limited by your hospital protocol, but in the world of theory, ruling out a PE is the most time-consuming difficult series of tests, some of which arent without their own risks (D-dimer, doppler, spiral CT, V/Q scan, pulmonary angiography...) that if you truly suspect PE (i.e. >50:50) then you start heparin. I believe its usually about 800-1200 Units per hour after a bolus, and you monitor with PTT (naturally) shooting for somewhere between 60-80.

How we do it:
suspect PE a little?
1) Order a CT with PE protocol.
2) Await results

suspect PE a lot?
1) Start heparin
2) Order a CT with PE protocol.
3) Await results

Go from there if the results are equivocal and the patient doesnt stabilize.

Key points:

If you really suspect DVT, follow the same protocol. Treat first, then image. Treatment of choice is LMWH.

 

[Idiopathic]

so what about for PE? Assuming a combo of the following are each listed as answer choices what's the recommended order if you go by the book?

ABGs
V/Q vs CT
Anti-coagulation

I'm assuming get the diagnosis first for board purposes...

Not necessarily. Patient 48-72 hours from surgery develops dyspnea, tachycardia, non-specific EKG changes (S1T3Q3 maybe?) and persistently low pulse ox needs no imaging before starting anticoagulation, even though these findings are not terribly specific. If you see this picture and dont anticoagulate, youve made the wrong choice.

Now, if someone walks into your clinic after having an outpatient knee scope a week ago, and theyve been doing fine at home, and have no systemic signs save for dyspnea and maybe tachycardia, thats probably a case for imaging first, since the risks of anticoagulation likely outweight the benefits/

 

[Idiopathic]

but if it's just a DVT, without suspicion for PE, then it's urgent but not an emergency. therefore the risk of anticoagulation outweighs the empiric benefits. thus a noninvasive DVT scan, which can be done fairly quickly, is a good initial step.

Just for your edification, the evidence states that if you truly suspect it (beefy red lower extremity, etc) you treat first. I would actuallt argue that treating a DVT is AT LEAST AS IMPORTANT as treating a suspected PE, since you are trying to prevent a PE with both treatments, but in one case (the DVT) you have a chance to eliminate the possibility of PE altogether.

 

[AbuSimpson]

but if it's just a DVT, without suspicion for PE, then it's urgent but not an emergency. therefore the risk of anticoagulation outweighs the empiric benefits. thus a noninvasive DVT scan, which can be done fairly quickly, is a good initial step.

Just for your edification, the evidence states that if you truly suspect it (beefy red lower extremity, etc) you treat first. I would actuallt argue that treating a DVT is AT LEAST AS IMPORTANT as treating a suspected PE, since you are trying to prevent a PE with both treatments, but in one case (the DVT) you have a chance to eliminate the possibility of PE altogether.

This was my thought with the initial post. Although I agree with many that "the risks of anticoagualtion must be weighed" I think that this is crap since we give prophylactic heparin to virtually every inpatient and many post-procedure patients who have TONS of risks of falling or bleeding while on it. And this particular question was about a heathy young woman.

So I think if the diagnosis is clinically clear that it's a DVT, I'm not sure if UW is right in getting a venous U/S before getting a bolus of heparin. Alternatively, maybe I've just seen too many people who are getting heparin in the hospital without evidence-based indications.

 

[Idiopathic]

Index of suspicion is key, but for that to be valid, people need to have actually seen a few PE's/DVT's and not textbook examples of them. So this may be why you see so many people get therapeutic anticoagulation in this scenario.

Also because its a ridiculously big legal pitfall to not treat a possible life-threatening condition (even if only 30% suspected) while waiting for imaging results.

 

[Diana_UC]

but if it's just a DVT, without suspicion for PE, then it's urgent but not an emergency. therefore the risk of anticoagulation outweighs the empiric benefits. thus a noninvasive DVT scan, which can be done fairly quickly, is a good initial step.

This was my thought with the initial post. Although I agree with many that "the risks of anticoagualtion must be weighed" I think that this is crap since we give prophylactic heparin to virtually every inpatient and many post-procedure patients who have TONS of risks of falling or bleeding while on it. And this particular question was about a heathy young woman.

So I think if the diagnosis is clinically clear that it's a DVT, I'm not sure if UW is right in getting a venous U/S before getting a bolus of heparin. Alternatively, maybe I've just seen too many people who are getting heparin in the hospital without evidence-based indications.

Yes, but again, just for clarification.... prophylactic heparin and treatment of DVT/PE are two very different anticoagulation risks.

 

[Diana_UC]

I have a question related to this, though...

What if you have a patient come in with obvious DVT and Signs/Sx of PE as well? Can you just go for the easier dx of DVT via dopplers since the anticoagulation treatment is the same for DVT and/or PE?

Or do you have to chase the PE with V/Q scanning, helical CT, etc....


Also, as far as Boards purposes go... for dx of PE, do you do VQ scan OR helical CT first if you have the option? In our hospital, we almost never do V/Q scanning, since we're not that good at it and way better at reading PE protocal CTs... but, for boards, do you want to screen first with V/Q?

 

[RastaMan]

Patient with dyspnea, tachycardia, other signs of PE plus big swollen foot = high probability of PE (Check out Well's score to quickly figure out probability).

Therefore, first start heparin then do confirmatory testing (helical CT and compression ultrasound - compression ultrasound is quicker so will probably be done first).

On the other hand, big swollen foot in a patient taking OCPs and cancer BUT no signs and sx of PE = probable DVT. Rule out with compression ultrasound. Start heparin only if positive ultrasound. This is because as an earlier poster mentioned, DVT by itself is not immediately life threatening.

 

[Idiopathic]

This is because as an earlier poster mentioned, DVT by itself is not immediately life threatening.

Here is where this gets dicey. treating a PE is not actually 'treating a PE' per se, but rather preventing a new one. Treating a DVT is essentially preventing a new PE as well, right, since they both likely come from the same source.

Also, careful with compression ultrasound, Homas/Moses testing, since these tests on an OBVIOUS DVT can break clot loose.

 

[Samoa]

Here is where this gets dicey. treating a PE is not actually 'treating a PE' per se, but rather preventing a new one. Treating a DVT is essentially preventing a new PE as well, right, since they both likely come from the same source.

Well, yes and no. Heparin therapy prevents propagation of an existing clot, which would also serve to prevent enlargement of any area of perfusion defect within the lung, as well as preventing further emboli from a DVT that obviously is prone to embolizing (not all DVTs will embolize, but we don't know which ones will or won't).