From the Guidelines
Cardiac arrest should be managed based on the initial heart rhythm, with shockable rhythms (ventricular fibrillation and pulseless ventricular tachycardia) requiring immediate defibrillation and non-shockable rhythms (asystole and pulseless electrical activity) requiring high-quality CPR and identification of reversible causes. The most recent and highest quality study, 1, provides the basis for this approach, emphasizing the importance of early rhythm identification and appropriate intervention. Key considerations in managing cardiac arrest include:
- Delivering a shock (120-200J biphasic or 360J monophasic) for shockable rhythms, followed by immediate CPR for 2 minutes before rhythm reassessment, as recommended by 1.
- Administering epinephrine 1mg IV/IO every 3-5 minutes for both shockable and non-shockable rhythms, with the suggestion of administering it after initial defibrillation attempts are unsuccessful for shockable rhythms, as stated in 1.
- Focusing on high-quality CPR without interruption and identifying potential reversible causes (the "H's and T's") for non-shockable rhythms, as emphasized by 1. The distinction between shockable and non-shockable rhythms is crucial, as defibrillation can rapidly convert shockable rhythms to an organized rhythm with perfusion, while non-shockable rhythms require focus on CPR quality and addressing underlying causes, as highlighted by 1. Survival rates are generally higher for shockable rhythms (15-40%) compared to non-shockable rhythms (less than 15%), as noted in the example answer, but the most recent study 1 does not provide specific survival rates, instead focusing on the importance of early and appropriate intervention. In real-life clinical practice, it is essential to prioritize the approach based on the most recent and highest quality evidence, which is 1 in this case, to optimize outcomes in terms of morbidity, mortality, and quality of life.
From the Research
Shockable vs Non-Shockable Cardiac Arrest
- Shockable cardiac arrest refers to ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT), which can be treated with defibrillation 2, 3, 4, 5, 6.
- Non-shockable cardiac arrest refers to pulseless electrical activity (PEA) or asystole, which cannot be treated with defibrillation 2, 3, 5.
Factors Associated with Shockable Rhythms
- Monitored cardiac arrest, witnessed cardiac arrest, and specific cardiac diseases (e.g. ischemic heart disease, dysrhythmias, and valvular heart disease) are associated with initial shockable rhythm 3.
- Higher age, female sex, and specific non-cardiovascular comorbidities (e.g. overweight and obesity, renal disease, and pulmonary cancer) are associated with an initial non-shockable rhythm 3.
Treatment and Outcomes
- The use of epinephrine during cardiopulmonary resuscitation (CPR) is recommended to increase coronary blood flow and perfusion pressure, but its beta-stimulation may have deleterious effects 2, 4.
- Beta-blockade has been studied as a potential treatment for cardiac arrest due to VF/VT, with some evidence suggesting it may reduce myocardial oxygen requirements and improve postresuscitation myocardial function 4.
- The incidence of VF has been noted to be progressively decreasing in multiple studies of out-of-hospital cardiac arrests (OHCA), likely due to improved medical and surgical therapies for ischemic heart disease and the widespread use of implantable cardiac defibrillators (ICDs) 5.