In these guidelines, the American Heart Association provides updated guidance for resuscitation of adults and children in cardiac arrest or with a life-threatening condition due to special circumstances, including anaphylaxis, asthma,cardiac arrest in the cardiac intervention suite, cardiac arrest following cardiac surgery, drowning, electrocution, gas embolism,high-consequence respiratory pathogens, hyperkalemia, hyperthermia, hypothermia, left ventricular assist device failure,pregnancy, pulmonary embolism, and poisoning due to benzodiazepines, β-blockers, calcium channel blockers, cocaine, cyanide,digoxin and related cardiac glycosides, local anesthetic systemic toxicity, methemoglobinemia, opioids, organophosphatesand carbamates, sodium channel blockers, sympathomimetics, and volatile hydrocarbons. Recommendations are alsoprovided for alternatives to cardiopulmonary resuscitation and the use of extracorporeal membrane oxygenation for poisonedpatients. Adults and children with these conditions require modification of basic life support and advanced life support. These guidelines are based on systematic evidence reviews and provide separate graded recommendations for adults and children.