May 12, 2025

Good morning, 

This month, we will be focusing on cardiac arrest care. The two most important aspects of cardiac arrest care are: 1) minimizing pauses in chest compressions and 2) defibrillating early and often if a patient is in a shockable rhythm. While we focused on chest compressions last week, we will concentrate on defibrillation this week.

Why is defibrillation important? 

If the patient is in cardiac arrest due to ventricular tachycardia (VT) or ventricular fibrillation (VF), defibrillation can correct the rhythm, leading to the return of spontaneous circulation (ROSC). Every minute a shock is delayed is associated with a ~10% greater chance of death. Given the importance of defibrillation, we want to shock every opportunity we have. This means we must perform rhythm checks every 2 minutes, so we never miss an opportunity to defibrillate.  

Use anterior-posterior pad placement as the default in cardiac arrest 

We have two options for pad placement: anterior-lateral (AL) and anterior-posterior (AP). Recent evidence supports the AP position having higher odds of ROSC over the AL position. A potential explanation for this is that the vector for the energy is directed more directly through the left ventricle when we defibrillate in the AP position. In addition, many of our patients are obese with large chest walls, so if we use the AL position, the energy might be directed too anteriorly and miss the heart entirely. For this reason, I recommend using the AP position as the default in cardiac arrest. When using the AP position, remember that both pads are placed to the left of the midline. We do not want to place the front pad underneath where we compress and the back pad directly over the spine. Please see the picture below for more details. 

Ways to optimize defibrillation 

We are always looking for ways to enhance how we perform cardiac arrest care. Here are some ways to optimize the process of defibrillation. 

1. Pre-charge the monitor BEFORE pulse/rhythm check. This allows us to shock the patient right after we see that the patient has a shockable rhythm. If we are doing manual CPR, this means we would not need to pause compressions a second time to deliver the shock after charging. If no shock is delivered, the energy will be dissipated automatically (often after the 60s), or the charge can be canceled manually. 

2. Perform compressions while charging the monitor. One of our main goals is to minimize pauses in chest compressions. If we see that the patient is in a shockable rhythm and we have not pre-charged the monitor, we should resume compressions while we charge the monitor and only pause again long enough to deliver the shock. 

3. If using a mechanical CPR (mCPR) device, do not pause compressions to shock. These devices are designed to perform compressions while defibrillations are delivered. For this reason, we should not pause compressions to deliver shocks when these devices are used.

4. Restart compressions immediately after shocking without re-checking pulse/rhythm. We should not delay restarting compressions after a shock to look for a rhythm change or feel for a pulse. The reason for this is it just prolongs the pauses in compressions. Our post-shock pause in compressions should ideally be <1 second if manual CPR and non-existent if mCPR, since we shock through compressions. The first time we re-check a pulse/rhythm after shocking is 2 minutes later at the next planned check. 

5. If the patient remains in VT/VF after 3 cycles of CPR with 3 consecutive shocks, we should consider using either vector change (VC) defibrillation or double sequential external defibrillation (DSED). The recent dose VF trial (Cheskes et al., NEJM 2022) was a randomized, controlled trial that found that DSED and VC each performed better than the standard of care in patients who failed to convert from VT/VF after 3 shocks. VC is where the pad orientation is changed (AP to AL or AL to AP) and only requires one monitor. DSED would require two monitors with two sets of pads attached to the patient (one in AP position and one in AL position). For DSED, both monitors shock in quick succession. These options are allowed in our protocol, and we should consider using these options when our standard shock has failed, since it would be the definition of insanity to keep trying the same thing, hoping for different results. 

Defibrillation is one of the cornerstones of cardiac arrest care. Understanding ways in which this process can be optimized helps us provide the best possible care for our cardiac arrest patients. 

Be safe and keep up the awesome work!

Jordan Singer, MD

EMS Medical Director, UH EMS Training and Disaster Preparedness Institute

Emergency Physician, UH Cleveland Medical Center

Emergency Physician, UH Elyria Medical Center

Assistant Professor, CWRU School of Medicine

May 5, 2025

Good morning, 

This month, we will focus on cardiac arrest care. Our number one goal in the treatment of cardiac arrest is for the patient to have a neurologically intact recovery. Our brain is everything we are, and we must preserve the brain to have the patients walk out of the hospital. There are two ways that we can achieve this goal: by minimizing pauses in chest compressions and by ensuring high-quality post-arrest care. Today, we will review why minimizing compressions is so critical and discuss ways we can minimize pauses.  

Why are pauses in compressions harmful? 

The purpose of chest compressions is to circulate blood to deliver oxygen to vital organs. The most important organs we are trying to preserve are the heart and brain. It takes time to build arterial pressure with this pressure dropping rapidly with even a few seconds of pause. For this reason, any pause in compressions (even if only for a few seconds) can be harmful to the brain and heart. It is also important to remember that the damage is cumulative. Therefore, even short pauses can add up to significant injury if there are enough of them. 

The impact of compression pauses on the heart 

We know that outcomes are often better for patients in a shockable rhythm because it is something that we can rapidly correct. However, without chest compressions, the heart is less likely to respond to a shock. In addition, if the pause in compressions is long enough, the rhythm might degenerate to a non-shockable rhythm. The picture below shows a potential scenario where a patient was in a shockable rhythm at the time of the initial call to 911. The patient did not receive bystander CPR, and by the time EMS arrived, the patient was no longer in a shockable rhythm. 

The impact of compression pauses on the brain 

Brain damage from lack of oxygen is irreversible. After four minutes without oxygen, the brain begins to be injured. After 5 minutes, brain cells die rapidly. If enough brain injury occurs, the patient might never wake up or be independent, even if we can get the heart beating again.  

If pauses in compressions are so bad, why do we pause every two minutes (or at all)? 

While chest compressions are critical, defibrillation for a shockable rhythm is equally important. This is because every minute a shock is delayed, it is associated with a ~10% greater chance of death. We need to balance shocking as early and often as possible with wanting to minimize compression pauses.  

What are ways that we can minimize pauses in compressions? 

1. Bystander CPR: This is debatably the single most important aspect of out-of-hospital cardiac arrest care. If this is not present, most of the damage might have already occurred prior to EMS arrival on the scene. Emergency medical dispatchers play a pivotal role if they can identify cardiac arrest over the phone and get the caller (or another bystander) to perform chest compressions, which can absolutely save a life. While many in EMS are not directly involved in dispatch, we still play an important role in bystander CPR. This is because local leaders lean on fire and EMS for expertise in prehospital care. We should use this as an opportunity to promote policies that can increase rates of bystander CPR. 

2. Do not pause compressions for placing advanced airways: if unable to place an endotracheal tube through compressions (which is not easy), place a supraglottic airway. 

3. Practice placing a mechanical CPR device in under 10 seconds. 

4. Pre-charge the monitor: this allows us to shock the patient the moment we confirm that the patient has a shockable rhythm. If we have not pre-charged the monitor, we should continue compressions while the monitor is charging and only pause to deliver the shock if doing manual CPR. As a reminder, we can defibrillate patients while mechanical CPR devices are running and should not pause them to shock. 

Understanding why pauses in compressions are so harmful helps us understand our specific priorities in cardiac arrest care. We should always focus on ways to further minimize pauses in compressions to achieve the best possible outcomes for our patients. 

Be safe and keep up the awesome work!

Jordan Singer, MD

EMS Medical Director, UH EMS Training and Disaster Preparedness Institute

Emergency Physician, UH Cleveland Medical Center

Emergency Physician, UH Elyria Medical Center

Assistant Professor, CWRU School of Medicine