Cardiac Arrest Algorithm

The current ACLS guidelines are set into several groups of "algorithms" - a set of instructions that are followed to standardize treatment, and increase its effectiveness. These algorithms usually come in the form of a flowchart, incorporating 'yes/no' type decisions, making the algorithm easier to memorize.



Hi, I'm Luke Gallagher and in this article we're going to talk about everything you need to know about one of the most important algorithms in ACLS, Cardiac Arrest Algorithm.

Firstly you're going to start with establishing unresponsiveness and right after that you're going to get some help coming, either activate the EMS or call the code if you're in the hospital.

You'll also be making sure they have enough oxygen and immediately begin high quality CPR that consists in :





🔵 Pushing hard (≥ 2 inches) and fast (100-120 beats/min) and allowing the patients chest to recoil (This is the concept of taking all of one’s weight off of the chest between each compression to allow the chest to fully expand, which creates a negative pressure that draws blood back into the heart. Drawing blood back into the heart is the only way tissue perfusion is actually able to occur. Tissue perfusion is the process of delivering blood - and, as a result, oxygen - to the vital tissues and organs of the body. )






🔵 If no advanced airway is available, then perform a 30:2 compression to ventilation ratio (Do not over ventilate (In the past decade, traditional CPR instruction included a compression to ventilation ratio of 30:2, and breaths were given during a pause in chest compressions. The degree of, and even the necessity of ventilation during CPR has recently been questioned. It is important to understand why over ventilation is bad, as in high pressure situations like cardiac arrest resuscitations, even highly trained providers excessively ventilate their patients.)






🔵 Minimize interruptions in compressions (10 seconds or less)






🔵 If the PETCO2 is <10mm Hg during CPR, it is reasonable to try to improve chest compressions and vasopressor therapy.


The next thing for you to establish, is if it's a shockable rhythm or not.

If the rhythm is not shockable, then we are talking about a PEA (Pulseless Electrical Activity) or Asystole. These are usually end of life rhythms and it's very important that you resume CPR with minimal interruptions, establish vascular access and administer, as the guidelines recommend, Epinephrine IV/IO 1mg every 3-5 minutes and Amiodarone IV/IO (first dose is 300 mg bolus, second dose is 150 mg). You should also consider advanced airway at 8 to 10 breaths per minute with continuous chest compressions and ETCO2 monitoring.


If a Return of spontaneous circulation (ROSC) occurs you proceed with the standard ABCDE approach, while making sure you find the main cause. You should also manage the patients temperature.


For shockable rhythms understand the following

Principle of Early Defibrillation 

The earlier defibrillation occurs, the higher the survival rate. When VF is present, CPR can provide a small amount of blood flow to the heart and brain but cannot directly restore an organized rhythm. The likelihood of restoring a perfusing rhythm is optimized with immediate CPR and defibrillation within a few minutes of the initial arrest. Restoration of a perfusing rhythm requires immediate CPR and defibrillation within a few minutes of the initial arrest.


Delivering Shock

The appropriate energy dose is determined by the identity of the defibrillator – monophasic or biphasic. If you are using a monophasic defibrillator, give a single 360-J shock. Use the same energy dose of subsequent shocks. Biphasic defibrillators use a variety of waveforms, each of which is effective for terminating VF over a specific dose range. When using biphasic defibrillators, providers should use the manufacturer’s recommended energy dose (eg, initial dose of 120 to 200 J). Many biphasic defibrillator manufacturers display the effective energy dose range on the face of the device. To minimize interruptions in chest compressions during CPR, continue CPR while the defibrillator is charging. Immediately after the shock, resume CPR, beginning with chest compressions. Give 2 minutes (about 5 cycles) of CPR. A cycle consists of 30 compressions followed by 2 ventilations in the patient without an advanced airway.


Synchronized shocks

cardioversion uses a sensor to deliver a shock that is synchronized with a peak of the QRS complex

Synchronized cardioversion uses a lower energy level than attempted defibrillation.

When to use synchronized shock:

Unstable SVT

Unstable Atrial Fibrillation

Unstable Atrial Flutter

Unstable regular monomorphic tachycardia with pulse


Unsynchronized shocks

Means that the electrical shock will be delivered as soon as the operator pushes the SHOCK button to discharge the device

May fall randomly anywhere within the cardiac cycle

When to use Unsynchronized Shocks:

For a patient who is pulseless

For a patient demonstrating clinical deterioration (in prearrest), such as those with severe shock or polymorphine VT, you think a delay in converting the rhythm will result in cardiac arrest.

When you are unsure whether monomorphic or polymorphic VT is present in the unstable patient.

Step by step

> Confirm cardiac arrest – check for signs of life and normal breathing, and if trained to do so check for breathing and a pulse simultaneously.

> Call resuscitation team.

> Perform uninterrupted chest compressions while applying self-adhesive defibrillation/monitoring pads – one below the right clavicle and the other in the V6 position in the midaxillary line.

> Plan actions before pausing CPR for rhythm analysis and communicate these to the team.

> Stop chest compressions; confirm VF/pVT from the ECG. This pause in chest compressions should be brief and no longer than 5 seconds.

> Resume chest compressions immediately; warn all rescuers other than the individual performing the chest compressions to “stand clear” and remove any oxygen delivery device as appropriate.

> The designated person selects the appropriate energy on the defibrillator and presses the charge button. Choose an energy setting of at least 150 J for the first shock, the same or a higher energy for subsequent shocks, or follow the manufacturer’s guidance for the particular defibrillator. If unsure of the correct energy level for a defibrillator choose the highest available energy.

> Ensure that the rescuer giving the compressions is the only person touching the patient.

> Once the defibrillator is charged and the safety check is complete, tell the rescuer doing the chest compressions to “stand clear”; when clear, give the shock.

> After shock delivery immediately restart CPR using a ratio of 30:2, starting with chest compressions. Do not pause to reassess the rhythm or feel for a pulse. The total pause in chest compressions should be brief and no longer than 5 seconds.

> Continue CPR for 2 min; the team leader prepares the team for the next pause in CPR.

> Pause briefly to check the monitor.

> If VF/pVT, repeat steps 6–12 above and deliver a second shock.

> If VF/pVT persists, repeat steps 6–8 above and deliver a third shock. Resume chest compressions immediately. Give adrenaline 1 mg IV and amiodarone 300 mg IV while performing a further 2 min CPR. > Withhold adrenaline if there are signs of return of spontaneous circulation (ROSC) during CPR.

> Repeat this 2 min CPR – rhythm/pulse check – defibrillation sequence if VF/pVT persists.

> Give further adrenaline 1 mg IV after alternate shocks (i.e. approximately every 3–5 min).

> If organised electrical activity compatible with a cardiac output is seen during a rhythm check, seek evidence of ROSC (check for signs of life, a central pulse and end-tidal CO2 if available).

> If there is ROSC, start post-resuscitation care.

> If there are no signs of ROSC, continue CPR and switch to the non-shockable algorithm.

> If asystole is seen, continue CPR and switch to the nonshockable algorithm.