nonshockable

Nonshockable is a term used in cardiopulmonary resuscitation (CPR) and emergency medicine to describe cardiac arrest rhythms for which defibrillation is not indicated. In the setting of cardiac arrest, heart rhythms are categorized as shockable (for example, ventricular fibrillation and pulseless ventricular tachycardia) and nonshockable (asystole and pulseless electrical activity, or PEA).

Asystole refers to the absence of electrical activity on the electrocardiogram and no mechanical heart activity. PEA refers to organized electrical activity on ECG without a detectable pulse or adequate perfusion. In both conditions, immediate high-quality CPR is required, and defibrillation is not the primary intervention, though rhythm checks and treatments follow established resuscitation guidelines.

Management emphasizes continuous chest compressions, airway management, and oxygenation. Epinephrine is commonly used during prolonged arrests. A key component is the rapid identification and treatment of reversible causes, often summarized as the Hs and Ts: hypovolemia, hypoxia, hydrogen ion (acidosis), hyperkalemia or hypokalemia, hypothermia, tension pneumothorax, tamponade, thrombosis (coronary or pulmonary), and toxins. Reversible conditions should be addressed as they are identified, and advanced life support measures, including consideration of an advanced airway and monitoring tools like capnography, may be employed.

Prognosis for nonshockable rhythms is generally poorer than for shockable rhythms, and outcomes depend on factors such as time to CPR, the underlying cause, and comorbidities. The term is widely used in clinical guidelines and practice to distinguish these scenarios from those where immediate defibrillation is appropriate.