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The Speed of Sound

Ultrasound Can Shorten Pulse Checks during CPR

Butts, Christine, MD

doi: 10.1097/01.EEM.0000554286.02732.06
The Speed of Sound

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The use of ultrasound in cardiac arrest has received some bad press over the past few years. It has been shown to prolong pulse checks and delay chest compressions. The recent REASON trial, however, demonstrated that ultrasound does have utility, at times powerfully so, in cardiac arrest. (Resuscitation 2016;109:33.)

The CASA exam (Cardiac Arrest Sonographic Assessment) was proposed as a standardized approach in treating PEA arrest to obtain a good assessment of the heart while minimizing pauses in CPR. (Am J Emerg Med 2018;36[4]:729; http://bit.ly/2TSykxd.) The idea is to perform a stepwise assessment with each pulse check rather than a full evaluation during one pause. The goal during the first break is to assess for the presence of a pericardial effusion. The right ventricle is examined for enlargement, which may indicate a massive pulmonary embolism in the second pause. Cardiac activity is assessed during the third pause. Evaluation for pneumothorax and a FAST exam can be performed while CPR is ongoing without affecting compressions.

The CASA exam creators also offer tips to minimize delays in CPR:

  • The subxiphoid approach is preferred because the sonographer can place the transducer in position before the pause, and this area is usually open during compressions.
  • A predetermined clinician other than the code leader should be designated to perform the ultrasound.
  • Have a verbal clock running during each pulse check to keep everyone focused on the time elapsing.

A study in Resuscitation assessed the length of pulse checks before and after implementation of the CASA protocol by evaluating videotaped resuscitations. (2018;131:69.) The average pulse check before the protocol took 19.8 seconds and 15.8 seconds after it was implemented. They also found that planning ahead for the pulse checks by getting the transducer in position beforehand saved 3.1 seconds, as did utilizing attending physicians with ultrasound fellowship training. The study design had a few methodological issues, but overall it seems that having an organized plan before pulse checks saves valuable seconds.

Recommendations from my experience? Put your probe in position early without disrupting CPR. Record a short clip and resume compressions without pausing to interpret the scan. Many machines have settings that allow you to select longer clip times. Once CPR has resumed, the clip can be scrutinized for signs of reversible causes of cardiac arrest (tamponade, PE) or subtle cardiac motion.

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Dr. Butts is the director of the division of emergency ultrasound and a clinical assistant professor of emergency medicine at Louisiana State University at New Orleans. Follow her on Twitter @EMNSpeedofSound, and read her past columns at http://bit.ly/EMN-SpeedofSound.

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