Professional Soldiers ® - View Single Post - 32 yo F with unilateral leg pain and swelling

Doczilla · 04-29-2008, 23:02

The high SaO2 was a little surprising in light of the tachycardia. Near as I can figure, it's because she had bilateral PE, but not a "saddle embolus", so blood was still making it through to be well oxygenated by her non-smoker lungs. And she's young and otherwise healthy, so I would expect her to compensate well. I quizzed her pretty thoroughly, and she denied any SOB, orthopnea, dyspnea on exertion, chest pain, cough, or fatigue. I frankly don't know why she wasn't more symptomatic.

EKG showed sinus tachycardia without any other findings. Normal axis, normal R-wave progression. There is another lesson here; as much as we talk about the S1Q3T3 pattern in PE, the most common EKG finding is sinus tachycardia. A-Fib can present with a hemodynamically significant PE, since the right atrium can't empty (because the right ventricle can't empty) and will stretch out and start fibrillating.

D-dimer can be mildly elevated by cellulitis, but usually not to the same extent as you see with DVT or PE. The D-dimer can be markedly elevated by sepsis, shock, DIC, and trauma.

Here's the key thing with D-Dimer: there are 5 forms, and the most sensitive form is the ELISA D-dimer (it's a process, not a brand). This has a greater than 99% negative predictive value in patients without confounding factors, meaning that as long as certain criteria apply, you can virtually rule out a significant PE or DVT with it. This is good for the young, otherwise healthy person with chest pain where PE is unlikely but possible. If you have a high pretest probability, like a person with clinically apparent DVT and tachycardia, or sudden onset chest pain/SOB after a long flight, then you'd skip the D-Dimer and get the CT and US. It's great to use in concert with US as well. A negative D-Dimer and negative US rules out DVT to great clinical certainty. If you don't have the D-Dimer, and you have a negative US, you would have to do a repeat US in a few days. D-Dimer is decidedly NOT helpful in patients who are old, have multiple comorbid diseases, cancer, or recent trauma. In these cases, it means nothing if it is negative or positive.

The less sensitive forms, such as the latex agglutination D-dimer, have lower NPV, like 90%. This means that with a negative test, you still have a 10% chance of having a significant clot. Might as well flip a coin.

I don't think SS's question was directed at me, so I'll let others chime in on that.

We can give CEUs for this, but we'd have to devise a test at the end.

'zilla

04-29-2008, 23:02	#8
Doczilla Guerrilla Join Date: Nov 2006 Location: Ohio, West Virginia Posts: 137	The high SaO2 was a little surprising in light of the tachycardia. Near as I can figure, it's because she had bilateral PE, but not a "saddle embolus", so blood was still making it through to be well oxygenated by her non-smoker lungs. And she's young and otherwise healthy, so I would expect her to compensate well. I quizzed her pretty thoroughly, and she denied any SOB, orthopnea, dyspnea on exertion, chest pain, cough, or fatigue. I frankly don't know why she wasn't more symptomatic. EKG showed sinus tachycardia without any other findings. Normal axis, normal R-wave progression. There is another lesson here; as much as we talk about the S1Q3T3 pattern in PE, the most common EKG finding is sinus tachycardia. A-Fib can present with a hemodynamically significant PE, since the right atrium can't empty (because the right ventricle can't empty) and will stretch out and start fibrillating. D-dimer can be mildly elevated by cellulitis, but usually not to the same extent as you see with DVT or PE. The D-dimer can be markedly elevated by sepsis, shock, DIC, and trauma. Here's the key thing with D-Dimer: there are 5 forms, and the most sensitive form is the ELISA D-dimer (it's a process, not a brand). This has a greater than 99% negative predictive value in patients without confounding factors, meaning that as long as certain criteria apply, you can virtually rule out a significant PE or DVT with it. This is good for the young, otherwise healthy person with chest pain where PE is unlikely but possible. If you have a high pretest probability, like a person with clinically apparent DVT and tachycardia, or sudden onset chest pain/SOB after a long flight, then you'd skip the D-Dimer and get the CT and US. It's great to use in concert with US as well. A negative D-Dimer and negative US rules out DVT to great clinical certainty. If you don't have the D-Dimer, and you have a negative US, you would have to do a repeat US in a few days. D-Dimer is decidedly NOT helpful in patients who are old, have multiple comorbid diseases, cancer, or recent trauma. In these cases, it means nothing if it is negative or positive. The less sensitive forms, such as the latex agglutination D-dimer, have lower NPV, like 90%. This means that with a negative test, you still have a 10% chance of having a significant clot. Might as well flip a coin. I don't think SS's question was directed at me, so I'll let others chime in on that. We can give CEUs for this, but we'd have to devise a test at the end. 'zilla __________________ You may find me one day dead in a ditch somewhere. But by God, you'll find me in a pile of brass. -Tpr. M. Padgett Last edited by Doczilla; 04-29-2008 at 23:10.
Doczilla is offline