ACLS providers may have to administer multiple shocks, but high-quality chest compressions and adequate ventilation are also extremely important. Your email address will not be published.
Save my name, email, and website in this browser for the next time I comment. Notify me of follow-up comments by email. Notify me of new posts by email. This site uses Akismet to reduce spam. Learn how your comment data is processed. Register today for online ACLS certification! What are Shockable Rhythms? What are the Shockable Rhythms? There are two shockable rhythms and two non-shockable rhythms. This continues every two minutes until the AED is turned off only at transfer of care, switching to an advanced monitor, or termination of resuscitation efforts.
The application of energy to the heart is not a jump-start, as it is often described. This is the human equivalent of turning a computer off and back on again.
After the shock is delivered, there are two possible outcomes: The rhythm may continue, or it may convert either back to a normal rhythm or to another type of cardiac arrest rhythm. There are two shockable rhythms in cardiac arrest: ventricular fibrillation v-fib and pulseless ventricular tachycardia pulseless v-tach. Treatment of shockable rhythms for prehospital providers is aimed at stopping the arrhythmia to allow the heart to restart.
This is done by utilizing high-quality CPR, bag-valve mask BVM ventilations, defibrillation, and medication epinephrine, amiodarone, lidocaine, etc. V-fib is the chaotic quivering of the ventricles of the heart. This quivering does not produce a pulse, as the ventricles are not actually contracting. This could be compared to a seizure of the heart.
Common causes of v-fib are problems in electrical activity flowing through the heart or damage to muscle that prevents it from receiving the impulses properly. In response they attempt to provide circulation to the brain and body by firing on their own, and fast. This fast pace causes the chambers of the heart not to fill properly, resulting in decreased blood flow.
As this continues the problem compounds and becomes pulseless v-tach. Common causes of pulseless v-tach include scarring of the heart, coronary artery disease, drug use, medication side effects, and electrolyte imbalances.
It is important to understand that ventricular tachycardia can present with a pulse. In these cases the muscles are contracting with each impulse, and blood is flowing to the body. The AED cannot detect a pulse, so that makes the pulse check very important. Failure to check for a pulse may result in shocking a patient who is not actually in cardiac arrest. Nonshockable rhythms are ones in which the electrical system may be working properly or be completely inoperable, but in either instance electrical therapy would not be likely to restore a normal rhythm.
As such the AED will not advise shock for these rhythms. There are two types of nonshockable rhythms, pulseless electrical activity PEA and asystole. PEA looks like an organized cardiac rhythm.
The electrical activity would normally cause the heart to beat and blood to flow, but in the case of cardiac arrest, each impulse does not generate blood flow. If we know the electrical activity of the heart is working appropriately, we can then surmise the problem lies within either the hydraulic blood or mechanical cardiac muscle system.
Problems with the hydraulic system mean there is not enough blood to circulate around the body. One main cause of hydraulic system failure is hypovolemia loss of blood due to trauma, dehydration, or internal bleeding. To fix this condition, we must stop the blood loss. This can be accomplished with direct pressure and tourniquets for external bleeding or tranexamic acid TXA for internal bleeding.
We must also replace the blood; preferably this is done with blood products. However, in the civilian prehospital setting, blood products are not readily available. Some common causes of mechanical restriction include cardiac tamponade and tension pneumothorax. To reverse these the prehospital provider must provide high-quality CPR, BVM ventilations, needle decompression to relieve pressure in the chest for a pneumothorax , and medication epinephrine.
Asystole is the absence of electrical activity in the heart. While there are many causes of asystole, typically it presents due to prolonged periods of v-fib or because the heart muscle has died due to lack of oxygen. The out-of-hospital treatment for asystole is to provide high-quality CPR and medications to treat reversible conditions.
Understanding what the AED is telling us can help to guide our expectations of patient care and outcome in out-of-hospital cardiac arrest. Regardless of the cause of cardiac arrest, your treatment must always be within your scope of practice. Be sure to follow local protocols, which should include high-quality CPR to maintain adequate perfusion to the brain and heart until advanced techniques such as medication and electrical therapy can be administered. Arias E, Xu J.
United States Life Tables, National Vital Statistics Reports, ; 68 7. Cardiac Arrest Registry to Enhance Survival. Delgado H. Principles of External Defibrillators.
IntechOpen, ; www. Mayo Clinic. Ventricular fibrillation, www. Ventricular tachycardia, www. Pulseless Electrical Activity. StatPearls [Internet], ; www. He has worked as a firefighter and paramedic in inner-city, rural, and military communities. Currently he serves as a full-time civilian firefighter for the U. He is also an EMS instructor trainer for the U. Reach him at rconktraining gmail.
Sign in. EMS World Expo. Current Issue. Issue Archives. Start Print Subscription. Renew Print Subscription. Blood stops flowing and the body tissues have to cope with the sudden lack of oxygen supply.
This is known as cardiac arrest. We can see the various electrical wave patterns of the heart in cardiac arrest using an electrocardiogram or ECG. There are four main rhythms you might see during a cardiac arrest:. Pulseless ventricular tachycardia and ventricular fibrillation 1 and 2 are shockable, largely because they tend to be caused by the electrical activity of the heart being thrown out of whack, and not by the heart muscle itself being badly damaged.
Hitting the heart muscle with a big dose of electrical energy acts a bit like hitting Ctrl-Alt-Delete on your computer or Alt-Command-Esc for the Mac users. A single shock will cause nearly half of cases to revert to a more normal rhythm with restoration of circulation if given within a few minutes of onset. These rhythms indicate that the heart muscle itself is dysfunctional; it has stopped listening to the orders to contract.
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