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In this lesson, we're going to cover pulseless arrest and ventricular fibrillation. And at the end of the lesson, we'll provide you with a Word about cardiac arrest rhythms in general.
Ventricular fibrillation, also known as VFib, and pulseless ventricular tachycardia, also known as V-tach, are lethal dysrhythmias that do not produce a pulse.
VFib is the most common initial dysrhythmia in cardiac arrest patients and will regress to asystole if it isn't treated in a short amount of time. That treatment includes rapid defibrillation.
Warning: Rapid defibrillation is vital. How vital? For every single minute that defibrillation is delayed, the chance of the patient surviving is reduced by a full 10 percent.
The key steps to treating VFib are as follows:
- Rapid assessment to confirm the patient's cardiac arrest
- Starting CPR
- Applying the defibrillator
- Delivering the first shock
- Performing high quality CPR
Performing high-quality CPR is equally vital, as is performing it with as few interruptions as possible. High-quality CPR is performed by giving cycles of compressions at a depth of 2 to 2.4 inches and at a rate of 100 to 120 compressions per minute, followed by 2 full rescue breaths that cause the chest to rise and fall.
Pro Tip #1: Equally important is changing the CPR compressor, if available, every 2 minutes to avoid fatigue. Compressor fatigue leads to a shallower compression depth and a slower than optimal rate, both of which significantly and detrimentally affect the quality of CPR being performed.
After the initial defibrillator shock has been delivered, it's important to then establish IV or IO access in order to deliver medications and fluids. The first medication that should be administered is epinephrine (or epi for short) at 1mg of the 1:10,000 concentration via rapid IV or IO push every 3 to 5 minutes.
After that initial dose of epi is delivered, a second shock is then given. At this point you should also consider placing an advanced airway with capnography.
Pro Tip #2: Remember that once an advanced airway is in place, your CPR compressions then become continuous. The compressions are still 100 to 120 per minute, along with the same depth, but you'll now deliver 1 breath every 6 seconds.
If the patient remains in persistent VFib following the initial defibrillator shock and the first dose of epi, the next medication to be given is amiodarone at 300mg via rapid IV or IO push.
A second dose of amiodarone can be given at 150mg. This dose can only be repeated one time after 3 to 5 minutes.
Successful treatment of VFib continues by:
- Providing high-quality CPR
- Reassessing the patient's cardiac rhythm every 2 minutes
- Delivering a defibrillator shock if the VFib remains present
- And giving medications as indicated.
A Word About Cardiac Arrest Rhythms
This Word section covers the dysrhythmias that do not produce a palpable pulse, which leads to cardiac arrest. It is crucial to recognize and treat these rhythms as quickly as possible to improve the patient's chances of survival.
Ventricular Fibrillation and Pulseless Ventricular Tachycardia
The origin of ventricular fibrillation is due to multiple ectopic ventricular pacemakers, which depolarize in a random and chaotic fashion and spread throughout the myocardium. This results in uncontrolled myocardial quivering, or fibrillating, and does not produce cardiac output or a pulse.
Ventricular fibrillation is clinically significant because it is a lethal dysrhythmia and, as mentioned already above, is the most common initial rhythm in sudden cardiac arrest for adult patients, and often occurring in public places or non-hospital settings.
As you've already learned, immediate defibrillation is vital when it comes to managing ventricular fibrillation. Ventricular fibrillation of relatively large amplitude is often initially seen but becomes less coarse and less responsive to defibrillation as minutes pass.
Myocardial ischemia or infarction and sudden cardiac rhythm disturbances are the most common causes of ventricular fibrillation in adults.
Ventricular tachycardia (V-tach), can present with or without a pulse. Pulseless V-tach can occur in patients with cardiac arrest.
While not as often as ventricular fibrillation, ventricular tachycardia can be witnessed as the first rhythm in cardiac arrest before it deteriorates further into ventricular fibrillation. Pulseless V-tach treatment is the same as ventricular fibrillation, as both require immediate defibrillation.
Asystole
The term asystole in cardiac arrest refers to ventricular asystole. Often, if you were to look at the monitor closely, you'll notice that there are still P-waves and atrial depolarization but no conduction to the ventricles. This results in a total absence of mechanical activity in the myocardium.
For obvious reasons, ventricular asystole does not produce a pulse because the ventricles are not beating. It is usually the result of untreated ventricular fibrillation that will eventually degenerate into fine VFib and ventricular standstill or asystole. Other causes of asystole include severe hypoxia, acidosis, or electrolyte abnormalities.
Pulseless Electrical Activity (PEA)
PEA is not a particular cardiac rhythm. Rather, it's a condition in which an organized cardiac rhythm is not accompanied by a palpable pulse. PEA can be caused by anything that impedes myocardial mechanical activity or causes profound shock.
Treatable causes of PEA include the H's and T's: hypoxia, hydrogen ion (acidosis), hypovolemia, hyperkalemia, hypothermia, toxins, cardiac tamponade, tension pneumothorax, pulmonary thrombosis, and coronary thrombosis.
