Cardiac Arrest Protocol for Shorter Pauses in CPR

By Michael Prats, MD


Implementation of the Cardiac Arrest Sonographic Assessment (CASA) protocol for patients with cardiac arrest is associated with shorter CPR pulse checks

Resuscitation October 2018 - Pubmed Link

Take Home Points

1. This study offers weak evidence that a POCUS cardiac arrest protocol might decrease pauses in compressions associated with performing ultrasound.

2. Unknown whether or not this benefit would have any effect on patient centered outcomes.

3. This supports continued focus on judicious use and careful timing of POCUS during cardiac arrest to minimize potential harms.


As a POCUS celebrity couple, ultrasound and cardiac arrest have a complicated and stormy relationship. First everything is great, and we’re so happy for them. It seems POCUS helps us with diagnosing causes and prognostication in arrest. Then we find out that this practice could lead to increased pauses in chest compressions. Then we find out maybe not everyone agrees on what even constitutes cardiac standstill. Then we say, “well lets just use TEE." Exhausting! Well, perhaps we can start to tackle these problems one at a time. This article uses a specific protocol to try to cut down on the potential for unnecessarily long pauses in chest compressions. If we can decrease the risk of longer pauses, we might be one step closer to keeping POCUS and cardiac arrest in a more stable place (and a safer practice for patients). These authors present their data before and after implementing this protocol.


Does the teaching of the CASA (cardiac arrest sonographic assessment) protocol lead to reduced CPR pause duration with ultrasound?


Single center, urban emergency department


  • Adult

  • Presenting in cardiac arrest


  • Traumatic arrest

  • Sustained ROSC prior to ED arrival

  • If no CPR pauses

  • If resuscitation was not video recorded

  • Arrest run by physician assistant (because they did not receive CASA training)


Pre and post intervention

Initially 2 resuscitation rooms had video capability. 4 in post-intervention period. Recorded "24 hours a day, 7 days a week" but only when turned on.

Collected data for 1 year, timing the pauses in chest compression during which point of care ultrasound was being used.

Intervention: All residents and attendings were trained in the CASA protocol in small group sessions. Also distributed online handouts and monthly reminders. Protocol posted in resuscitation bays. POCUS use still considered optional in cardiac arrest.

All study videos reviewed by two reviewers. Noted CPR pause duration, reason for pauses, whether ultrasound was performed, presence of automated compression device, any procedures performed.

Primary outcome was difference in CPR pulse check duration when POCUS was performed between the pre and post interventions.

Powered to detect 4 second difference between CPR pulse check duration.

Secondary outcomes

  • Difference in CPR pause duration without POCUS

  • Effect of ED US fellowship training, procedures, year of training, placement of US on chest prior to stopping

Multivariable linear regression performed including pre or post intervention, attending ultrasound fellowship training, resident training year, procedure performed, if US on chest prior to stopping CPR, if same provider led code and performed ultrasound.

Who did the ultrasounds?

Emergency medicine residents and faculty

The Scan

Phased array transducer *(curvilinear can also be used during arrest - this protocol specified phased array preferred)


CASA Protocol

During First Three Pauses

1) First pause → Evaluate for tamponade

2) Second pause → Evaluate for pulmonary embolism

3) Third Pause → Evaluate for cardiac activity

During CPR

  • Evaluate for pneumothorax

  • Check IVC and FAST scan


5 Minute Sono - Obtaining Cardiac Windows

5 Minute Sono - Pericardial Effusion

5 Minute Sono - Cardiac Function


The POCUS Atlas - Echo

The Evidence Atlas - Cardiac Arrest


38 videos Pre

45 videos Post

160 pulse checks Pre. POCUS in 100 (62.5%)

140 pulse checks Post. POCUS in 110 (78.6%)

The Patients

  • Overall, pretty similar between groups

  • Post intervention group had more hypertension, more end-stage renal disease

  • Post group had more nonshockable rhythms (83.3% vs 65.8%)

  • Post group had less out of hospital cardiac arrest

  • Similar survival to ROSC (Pre 10% vs Post 12%) BUT if looking at all of the codes during those time periods (not just the video recorded), pre was 44% and post was 25%.

  • Similar trend for survival to admission

  • Median of 4 (pre) and 3 (Post) pauses per code

  • Both groups median 3 pulse check per code and 2 pauses with POCUS by code

Primary Outcome

Duration of Pulse Checks with POCUS

Pre-intervention - 19.8 seconds (17.9-21.7)

Post-intervention - 15.8 seconds (14.4-17.2)

Difference 4 seconds

Multivariate regression - Post was 3.3 seconds shorter duration in pulse checks with POCUS

Secondary Outcomes

Attending ultrasound fellowship training - 3.1 second shorter pauses

Placement of ultrasound prior to stopping CPR - 3.1 second shorter pauses

No association between pause duration and automated compression device, resident year or procedures being performed.

Pre-intervention group - 10% Pulse checks ≤ 10 seconds, Post-intervention group 19% Pulse checks ≤ 10 seconds (p = 0.06)

2.6 second decrease in duration of pulse checks WITHOUT POCUS (p = 0.18) between pre and post groups

Pulse checks without POCUS were 15.4 second pre (compared to 19.8 second with POCUS) and 12.8 seconds post (compared to 15.8 with POCUS).

Pauses not significantly longer when providers leading resuscitation performed POCUS.


Pre and post design. The main problem here is that, more than likely, more than one thing changed between the pre-intervention period and the post-intervention period. Ideally, the authors would like to say, “The only difference between the populations was the implementation of the CASA exam; and therefore, the decreased time for pauses was due to the CASA exam.” Fortunately, the pre and post time periods were over a fairly short period of time, so there is likely no huge game-changing cardiac arrest interventions that would differ between groups. However, we don’t know what else could have changed that could have confounded this result.

One concern is that there is no information on how often CASA was used. We don’t even know if the intervention lead to increased CASA protocol use. Furthermore, the time of CPR pulse check duration without POCUS decreased by 2.6 seconds. So maybe 2.6 seconds (15.4-12.8) was saved just based on changes in cardiac arrest management between the pre and post groups. That would weaken the implication that the CASA was responsible for the four second difference between the pre and post groups with POCUS. Therefore, it is really hard to say there is causation here.

Missed a lot of arrests. Pre-intervention 91/129 (70.5%) were excluded because no video or no pause in video. Post intervention much better - only 13/58 (22.4%) excluded. Having more rooms that recorded helped (39 pre, 0 post), but it was more than that. They remembered to record more often (pre 45 excluded because no video recorded, post 7). This makes me think there was more emphasis on recording and collecting the data. This was an unblinded study, meaning that everyone participating knew that it was being studied. There easily could have been a significant Hawthorne effect.


Extra POCUS performed in post group - is that good or bad? There was 62.5% of POCUS use in pulse checks in the pre group and 78.6% in the post group. We don’t know if POCUS was not being used in cases it should have in the first group, or if it was being overused in the second. Too little = maybe missing out on opportunity for POCUS to help. Too much = maybe ultrasound is causing more harm than good. There is probably a “goldilocks” phenomenon of finding the exact right amount of use, but there no real data to suggest what exactly that is. This group is trying to argue that three checks, per their protocol, is the right amount.

The other factors that had impact on pause time are interesting. Placing probe on chest and having an US fellowship trained faculty saved almost as much time as the CASA protocol! It is good to know that these factors are helpful, as they encourage appropriate ultrasound use. As a reminder, the best practices for US in arrest are:

  • Be prepared for scan prior to rhythm check. Have transducer on patient getting window prior to stopping compressions.

  • Save clip, don’t waste time interpreting in real time. Interpret after compression have restarted

  • Have some objective timer to limit time off the chest

  • Consider TEE instead of TTE

However, if doing this the right way saves 3 seconds and the CASA protocol saves 4 seconds, is the CASA protocol really necessary? This ties into the next point.

Is a 4 second difference clinically relevant when the pulse checks are (unfortunately) way above 10 seconds anyways? If CASA saves 1 second more than placing the probe on the chest prior to stopping, is it worth it? Of course we all know that we need to minimize the time that the coronary arteries are not being perfused BUT how much time makes a difference? When the mortality of these patients is low to begin with, it would be hard to prove a significant difference in outcomes without (approximately) a billion patients. It was nice that these authors looked at neurologic function in survivors (cerebral performance score of 1 or 2), but unsurprisingly, there was no real difference between groups (5.3% in Pre, 4.4% in Post). We may never get data to prove that there would be a difference in mortality or neuro outcomes, so we may have to continue basing our management on extrapolating data showing that more pauses are bad.

Take Home Points

1. This study offers weak evidence that a POCUS cardiac arrest protocol might decrease pauses in compressions associated with performing ultrasound.

2. Unknown whether or not this benefit would have any effect on patient centered outcomes.

3. This supports continued focus on judicious use and careful timing of POCUS during cardiac arrest to minimize potential harms.

Our score

3 Probes

Other Sweet FOAMed on this Article

REBEL EM - The CASA Exam: A Follow Up Study

Cite this post as

Michael Prats, MD. Cardiac Arrest Protocol for Shorter Pauses in CPR. Ultrasound G.E.L. Podcast Blog. Published on October 29, 2018. Accessed on April 14, 2021. Available at
Published on 10/29/18 06:00 AM
comments (2)
By John Bailitz on 11/02/18 03:15 PM
Su Casa is now Mi CASA. Great Podcast Creagh, Mike and Jacob - Thank you for creating the wonderful resource for our CUS community!
By Mike Prats on 11/05/18 09:42 AM
Thanks for listening John! We really appreciate the encouragement!