New in EM 007: Is RV dilation on PoCUS useful to diagnose PE during a cardiac arrest?

Originally Published on RCEM Learning Podcast June 2017

As part of the RCEM Learning Podcast I record reviews of recent literature with Dave McCreary. We’ve been doing this for about a year now and you can hear them all on the RCEM Learning Podcast each month. I’d like to have them here and searchable on this site too so I’ll be posting the ones I find most relevant here. You can hear the newest ones by subscribing to the free RCEM Learning Podcast. 

Audio:

“Is RV dilation on PoCUS useful to diagnose PE during a cardiac arrest”

Authors: Dave McCreary, Andy Neill

Codes: CC21,U8, HMP2

Clinical Question:

• Is RV dilation on PoCUS useful to diagnose PE during a cardiac arrest

Title of Paper:

• Detection of Pulmonary Embolism During Cardiac ArrestUltrasonographic Findings Should Be Interpreted With Caution

Journal

• Critical Care Medicine, 2017

Author

• Aagaard

Background

• PE is on everyones list of Hs and Ts during a cardiac arrest. If the patient is in arrest from a PE then they probably should received thrombolytics and we probably should continue CPR long enough for those lytics to take effect
• A potential tool for this is PoCUS. We know big PEs cause RV dilation in shocked patients so why not big RVs in dead people?

Patients studied

• Female crossbred Landrace/Yorkshire/Duroc pigs (27 32 kg) So not people then…
• This is pure animal work
  • Lab setting
  • Anaesthetised pigs with a nice model of cardiac from PE and other causes. They created the PE by taking some of the pigs own blood into a glass jar, letting it clot and then injecting it back in.
  • Lots of monitoring

What they did

• Compared 3 different models of porcine cardiac arrest
  • PE
  • Hypoxia
  • VF
• Took lots of pre and intra arrest transthoracic echocardiograms (they actually had to remove part of rectus abdominus to get the view and cant recommend that in humans)
• They then compared them all to see if RV dilation during a pulse check reliably predicted PE

What they found

• 24 pigs, 8 in each of the 3 groups
• All groups had RV dilation and it was slightly more in the PE group but not enough to be in any way meaningful
• (they actually had a sub study where they showed a bunch of docs the images and asked them to distinguish between moderate and severe RV dilation and they couldnt do it suggesting that any differences in the amount of RV dilation are not clinically meaningful

Bottom line

• In pigs (and probably in humans) during cardiac arrest the RV tends to dilate no matter what the cause. PEs make it a little bigger but not in any clinically useful manner. Dont get too trigger happy with your tPA just cause the RV looks a bit big in a dead patient. If theyre shocked but not dead, whole different story