Adult Cardiac Arrest

Cardiac arrest is the heart stopping as an effective pump. No pulse and no effective breathing confirm it. The 2025 AHA guidance sorts the rhythms into two groups. The shockable ones are ventricular fibrillation and pulseless ventricular tachycardia. The non-shockable ones are asystole and pulseless electrical activity.

• Mechanism: Most adult out-of-hospital arrests start in the heart itself, usually as ventricular fibrillation from acute coronary syndrome. In-hospital arrests often follow respiratory or circulatory failure, with a non-shockable rhythm.
• Survival depends on: Immediate high-quality CPR. Early defibrillation for shockable rhythms. Treating the underlying cause.
• Outcome: Survival to discharge is low overall. After ROSC comes post-arrest care (see Part 11 in References).

Typical Presentation

• Collapse: unresponsive with no pulse. Often witnessed. Sometimes it follows chest pain or a known cardiac history.
• Agonal breathing: slow, gasping breaths are not normal breathing. Start CPR.

Red Flags

• Pulse check longer than 10 seconds or uncertain pulse: treat as no pulse and start CPR
• Rhythm on the monitor: VF or pulseless VT (shockable) versus asystole or PEA (non-shockable)
• Abrupt rise in EtCO₂ during CPR, which can signal ROSC (2025 AHA Part 9, COR 2b). The 2025 text gives no absolute cutoff.

The arrest diagnosis is clinical. You analyze the rhythm and search for reversible causes during CPR. Neither one gets to delay compressions or defibrillation.

• Syncope with a pulse: feel for a palpable pulse before you start CPR. Poor perfusion with a pulse is not arrest.
• Profound hypothermia: Don't wait. Start full resuscitation now and keep it going through rewarming (COR 1; see Special Populations).
• Drowning or respiratory arrest: CPR with breaths is recommended (COR 1, B-NR). Most of these arrests are hypoxic in origin.

1. Scene safety and recognition: confirm unresponsiveness and absence of normal breathing; call for help and an AED.
2. Start CPR: place the heel of one hand on the center of the chest (lower half to lower third of the sternum) and compress at least 2 in (5 cm) and no more than 2.4 in (6 cm) deep, at 100–120 per min, with full chest recoil (2025 AHA Part 7: hand position COR 1, C-LD; depth COR 1, B-NR; rate COR 2a, B-NR). Minimize interruptions and keep each pause as short as possible.
3. Attach the AED or monitor-defibrillator: place pads in an anterolateral position (one on the upper right chest below the clavicle, one on the left side of the chest below the armpit) or an anteroposterior position (2025 AHA Part 7, COR 2a, C-LD; the two are comparably effective); defibrillate shockable rhythms immediately and resume CPR at once.
4. Ventilate: without an advanced airway, give 30 compressions to 2 breaths (30:2; 2025 AHA Part 7, COR 2a, B-NR); pause compressions to deliver 2 breaths, each over about 1 second, with enough volume for visible chest rise (COR 2a, C-LD); avoid excessive ventilation (COR 3: Harm, C-LD). With 2 or more rescuers, switch compressors about every 2 min (COR 2a, B-R).

Termination of resuscitation (2025 AHA Part 9, recs 1–5)

• BLS prehospital professionals use the BLS TOR rule for adult out-of-hospital cardiac arrest where ALS is not available or may be significantly delayed (COR 1, B-NR).
• ALS prehospital professionals may use the ALS TOR rule to end field resuscitation (COR 2a, B-NR).
• In a tiered EMS system with both ALS and BLS professionals, the Universal TOR rule is reasonable (COR 2a, B-NR).
• In intubated patients, failure to reach an end-tidal CO₂ above 10 mm Hg by waveform capnography after 20 minutes of ALS resuscitation may be considered as one component of a multimodal approach to deciding when to end efforts (COR 2b, C-LD).
• Harm: in non-intubated patients, a specific end-tidal CO₂ cutoff at any time during CPR should not be used to end resuscitative efforts (COR 3: Harm, C-EO).

Each rule applies within the scope of practice it was validated for. Use the rule your system has adopted. Criteria unclear? Call medical direction.

Every dose below comes from the 2025 AHA Adult Cardiac Arrest Algorithm (Drug Therapy).

• Access (Paramedic/RN/CCT): IV access first; intraosseous access if IV access is not quickly obtained. See IO Access.
• Shockable rhythm: defibrillate, resume CPR immediately, and give epinephrine after the initial defibrillation attempts have failed. Vector change (anterior-posterior pads) and double sequential defibrillation for VF/pVT still going after 3 or more consecutive shocks? Their usefulness is not established (2025 AHA Part 9, COR 2b). See Defibrillation.
• Epinephrine: 1 mg (10 mL of 0.1 mg/mL) IV/IO every 3–5 min. Non-shockable rhythm (asystole, PEA): give as soon as feasible after access. Shockable rhythm: after the initial defibrillation attempts have failed (2025 AHA Part 9: COR 1 for giving epinephrine; COR 2a, B-R for 1 mg every 3–5 min; COR 2a, B-NR for timing). See Epinephrine IV.
• Shock-refractory VF/pVT: amiodarone 300 mg IV/IO first dose, then 150 mg second dose; or lidocaine 1–1.5 mg/kg first dose, then 0.5–0.75 mg/kg. Either may be considered (2025 AHA Part 9, COR 2b, B-R); the algorithm gives them after the third shock. See Amiodarone and Lidocaine.
• Advanced airway: it comes after early CPR, defibrillation and drugs. If placing it would interrupt compressions, wait until the patient fails initial CPR and defibrillation attempts or achieves ROSC (2025 AHA Part 9, COR 1). Bag-mask ventilation, a supraglottic airway or an endotracheal tube may all be used, depending on setting and skill set (COR 2a or 2b). Once it is in place, 1 breath every 6 seconds (about 10/min) with continuous compressions may be reasonable (2025 AHA Part 9, COR 2b). Confirm placement with waveform capnography (COR 1). See Supraglottic Airway and Intubation.
• Not recommended routinely: sodium bicarbonate, calcium and magnesium in undifferentiated arrest (COR 3: No Benefit). Vasopressin, alone or with epinephrine in place of epinephrine (COR 3: No Benefit). Corticosteroids have uncertain benefit (COR 2b). Atropine has no routine recommendation for asystole or PEA. The 2025 text cites mixed observational data, and atropine is not in the algorithm. See Sodium Bicarbonate, Calcium Chloride and Magnesium Sulfate.

• Hemodynamics: keep mean arterial pressure at least 65 mm Hg (2025 AHA Part 11, COR 1, B-R). The evidence does not single out one vasopressor (COR 2b). Norepinephrine may be needed.
• Oxygenation and ventilation: after ROSC, give 100% inspired oxygen until SpO₂ or PaO₂ can be reliably measured (2025 AHA Part 11, COR 1, B-R). Avoid hypoxemia (COR 1, B-NR). Once saturation is reliable, titrate oxygen to SpO₂ 90–98% to avoid hyperoxia and hypoxemia (COR 2a). Be aware that pulse oximetry carries a higher risk of inaccuracy in patients with darker skin pigmentation, and that inaccuracy may conceal hypoxemia (COR 2b, C-LD). In patients who remain comatose, keep PaCO₂ at 35–45 mm Hg (COR 1).
• Temperature and glucose: maintain 32–37.5 °C under a deliberate temperature-control strategy, for at least 36 hours in patients who do not follow commands (2025 AHA Part 11, COR 1 and 2a). Avoid glucose below 70 mg/dL or above 180 mg/dL (COR 2b).
• Neurologic: treat clinically apparent seizures. In patients who do not follow commands, use EEG to diagnose them (2025 AHA Part 11, COR 1). Base neuroprognosis on a multimodal assessment, never on a single finding. Finalize it at least 72 h after normothermia and sedative discontinuation (COR 1 and 2a).
• Diagnostics: get a 12-lead ECG as soon as feasible (2025 AHA Part 11, COR 1). Emergent coronary angiography is for a suspected cardiac cause with ST elevation (COR 1). It also fits selected patients without ST elevation who have cardiogenic shock, recurrent ventricular arrhythmia or significant ongoing ischemia (COR 2a). In comatose patients without ST elevation, shock or instability, emergent angiography is not recommended over a delayed strategy (COR 3: No Benefit).
• Extracorporeal support: ECPR programs should develop and reassess their selection criteria (2025 AHA Part 4, COR 2a, C-LD). Intra-arrest transport for ECPR may be considered for limited, highly selected adult OHCA patients (COR 2b, B-R, 2025 AHA Part 4). The 2025 Part 9 text has no VF/pVT-specific ECPR recommendation. ECPR is reasonable for pregnant or peripartum patients not responsive to standard resuscitation. It is also reasonable for anaphylaxis refractory to drugs (COR 2a, 2025 AHA Part 10). See ECMO.

Targets and exceptions sit in Part 11 of References.

• Destination: Patients with ROSC need a center that can perform coronary angiography and post-arrest care.
• In transit: continue CPR when indicated. Monitor EtCO₂, rhythm, blood pressure and SpO₂. Keep the airway secured. Avoid hypotension and hypoxia.
• Handoff: time of arrest and of ROSC, number of shocks, drug times and doses, rhythm history, cause identified, and temperature if measured.

• Pediatrics: the compression-to-ventilation ratio and drug doses are both weight-based, and they differ. See Pediatric Cardiac Arrest and weight-based dosing.
• Pregnancy: maternal resuscitation comes first. That means manual left lateral uterine displacement (COR 1), the usual drugs and shocks, and early airway management. If the fundal height is at or above the umbilicus and standard resuscitation does not achieve ROSC, resuscitative delivery (perimortem cesarean) is indicated (2025 AHA Part 10, COR 1, B-NR). Start preparing at recognition. The goal is delivery by 5 minutes. Avoid excessive ventilation.
• Hyperkalemia: IV calcium, insulin with dextrose and sodium bicarbonate are the cause-directed options, but their effectiveness in hyperkalemic arrest is not well established (2025 AHA Part 10, COR 2b); inhaled beta-agonists are not recommended (COR 3: No Benefit). Adult arrest regimen (evidence grades from 2025 AHA Part 10 recs 1–4; drug doses from the E3 hyperkalemia regimen, insulin-dextrose per AHA Table 3): calcium chloride 10% 10 mL (1 g) IV/IO push (COR 2b, C-LD); sodium bicarbonate 50 mEq (one 50 mL vial of 8.4%) IV/IO, repeated every 5–10 min guided by blood gas (COR 2b, C-EO); flush or use a separate line between calcium and bicarbonate. Regular insulin 10 units IV over 15–30 min with 50 g IV dextrose (COR 2b, C-EO). Do not give albuterol in arrest (COR 3: No Benefit, C-EO). Differs from UKKA 2026 and ERC: those give 25 g (plus D10 50 mL/hr if glucose is under 126 mg/dL). AHA 2025 Table 3 gives 50 g. AHA rates insulin-glucose in hyperkalemic arrest COR 2b (effectiveness not well established). Outside arrest, see Calcium Chloride, Sodium Bicarbonate and Dextrose.
• Opioid overdose: ventilate first, with breaths or bag-mask (COR 1). Give naloxone for respiratory arrest with a pulse (COR 1). In cardiac arrest it may be reasonable, if it does not interfere with high-quality CPR (COR 2b). Adult dose: 0.2–2 mg IV/IO/IM or 2–4 mg intranasal, repeated every 2–3 min (house dosing; see Naloxone). The FDA label (naloxone HCl injection, DailyMed) starts at 0.4–2 mg IV, repeated at 2–3 min intervals. So the starting dose differs by label.
• Accidental hypothermia: Full resuscitation starts at once and runs through rewarming (COR 1). Defibrillate once. Then hold further shocks and epinephrine until the core temperature is 30 °C or higher (COR 2b). ECLS rewarming is reasonable (COR 2a) (2025 AHA Part 10).
• Pulmonary embolism: when confirmed PE is the cause, systemic fibrinolysis, surgical embolectomy or percutaneous mechanical embolectomy are reasonable (COR 2a, B-NR). For suspected PE, systemic fibrinolysis may be considered (COR 2b) (2025 AHA Part 10).
• Drowning and respiratory arrest: follow a ventilation-first pathway. CPR with breaths is recommended (COR 1, B-NR). Trained rescuers may start with breaths (COR 2b). Cardiac arrest after drowning is most often hypoxic in origin (2025 AHA Part 10).
• Anaphylaxis and severe asthma: in anaphylactic arrest epinephrine remains the key drug (see Epinephrine IM for pre-arrest dosing). Give isotonic IV fluid resuscitation alongside it (2025 AHA Part 10, COR 2a). The effectiveness of the standard IM epinephrine dose in arrest is uncertain (COR 2b). In severe asthma, use a low respiratory rate and tidal volume (COR 2a). Evaluate for tension pneumothorax if peak pressures suddenly rise (COR 1).

• Error: stopping compressions for long rhythm or pulse checks. Keep the pauses short.
• Error: routine calcium, bicarbonate or magnesium in undifferentiated arrest. Save them for a specific cause.
• Error: mixing up epinephrine concentrations. The arrest dose is 1 mg: 10 mL of 0.1 mg/mL (1:10,000), or 1 mL of 1 mg/mL (1:1,000) diluted 1:10 to 10 mL of 0.1 mg/mL. Never give 10 mL of the 1 mg/mL product. That is 10 mg. Confirm concentration and volume.
• Error: holding defibrillation to give drugs. Shock as soon as the rhythm allows.
• Error: waiting on epinephrine in PEA or asystole. Give it as soon as feasible after access.