5 Adult ACLS Algorithms

Initial decisions and team response

Adult Advanced Cardiovascular Life Support (ACLS) organizes emergency care around three rapid decisions: whether a pulse is present, whether the rhythm is shockable, and whether the patient is unstable. Begin with immediate assessment and support, then follow the pathway matching the patient’s condition. These algorithms are for trained healthcare providers and do not replace clinical judgment, local protocols, or hands-on ACLS training.

If no definite pulse is found within $10$ seconds, treat the situation as cardiac arrest and begin CPR. Do not delay compressions to identify the exact rhythm. If a pulse is present with bradycardia or tachycardia, determine whether the rate is causing cardiopulmonary compromise; treat the patient’s condition rather than the monitor reading alone.

For unstable tachyarrhythmia with a pulse, prepare for synchronized cardioversion. Use an unsynchronized shock (defibrillation) for polymorphic ventricular tachycardia or when synchronization is not possible in a critically unstable patient. Throughout resuscitation, assign team roles, communicate rhythm and treatment decisions aloud, and minimize interruptions to chest compressions.

Pulseless cardiac arrest

Begin high-quality CPR, provide bag-mask ventilation with oxygen, and attach a monitor/defibrillator. Check the rhythm about every $2$ minutes, keeping pauses brief. The first major decision is whether the rhythm is shockable.

• Shockable: ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT).

• Not shockable: asystole or Pulseless electrical activity (PEA). PEA is organized electrical activity without a palpable pulse and is not treated with defibrillation.

VF and pulseless ventricular tachycardia

For VF/pVT, deliver a shock and immediately resume CPR for $2$ minutes; obtain IV/IO access. Recheck the rhythm. If VF/pVT persists, shock again and immediately resume CPR. Give epinephrine $1\ \text{mg}$ IV/IO every $3\text{–}5$ minutes during ongoing resuscitation, and consider an advanced airway and waveform capnography.

Recheck the rhythm again. If it remains shockable, deliver another shock and immediately resume CPR. Give amiodarone or lidocaine for refractory VF/pVT and treat reversible causes. Continue CPR, rhythm checks, and the shockable-rhythm sequence as indicated. If the rhythm becomes nonshockable, move to the PEA/asystole pathway; if Return of spontaneous circulation (ROSC) occurs, transition to post-arrest care.

For a biphasic device, use the manufacturer-recommended defibrillation setting, commonly an initial $120\text{–}200\ \text{J}$. If the recommended setting is unknown, use the maximum available. Subsequent shocks should be equivalent, with higher energy considered when appropriate. For a monophasic device, use $360\ \text{J}$.

For refractory VF/pVT, the antiarrhythmic options and doses are:

• Amiodarone $300\ \text{mg}$ IV/IO bolus, then $150\ \text{mg}$ if needed.

• Lidocaine $1\text{–}1.5\ \text{mg/kg}$ IV/IO, then $0.5\text{–}0.75\ \text{mg/kg}$ if needed.

PEA and asystole

Begin or continue CPR in $2$-minute cycles, establish IV/IO access, and give epinephrine $1\ \text{mg}$ IV/IO as soon as possible, then every $3\text{–}5$ minutes. Consider an advanced airway and waveform capnography. Recheck the rhythm about every $2$ minutes; if it becomes VF/pVT, switch to the shockable pathway. Search for and treat reversible causes. Do not defibrillate PEA or asystole.

CPR quality and reversible causes

For adults, perform chest compressions at $100\text{–}120$ per minute to a depth of at least $5\ \text{cm}$ ($2\ \text{inches}$). Allow full chest recoil and minimize pauses. Without an advanced airway, use a compression-to-ventilation ratio of $30:2$. With an advanced airway, continue compressions and give $1$ breath every $6$ seconds, or $10$ breaths per minute. Avoid excessive ventilation. Change compressors about every $2$ minutes or sooner if fatigued.

Consider the Hs and Ts as reversible causes during cardiac arrest:

• Hs: hypovolemia, hypoxia, hydrogen ion (acidosis), hypo-/hyperkalemia, and hypothermia.

• Ts: tension pneumothorax, cardiac tamponade, toxins, pulmonary thrombosis, and coronary thrombosis.

Bradycardia with a pulse

A heart rate typically below $50$ per minute may represent bradyarrhythmia, but the key question is whether the rate is inappropriate for the patient and causing cardiopulmonary compromise. Look for hypotension, acutely altered mental status, signs of shock, ischemic chest discomfort, or acute heart failure.

If there is no cardiopulmonary compromise, support airway, breathing, and circulation; consider oxygen; obtain a $12$-lead ECG when available; and observe while identifying or treating the underlying cause.

If compromise is present, support airway and breathing, provide oxygen as indicated, attach a monitor, and monitor the pulse. If compromise persists, give atropine $1\ \text{mg}$ IV, repeating every $3\text{–}5$ minutes to a maximum total dose of $3\ \text{mg}$.

If atropine is ineffective, use transcutaneous pacing and/or an epinephrine infusion of $2\text{–}10\ \text{mcg/min}$ or a dopamine infusion of $5\text{–}20\ \text{mcg/kg/min}$, titrated to response. Seek expert help and consider transvenous pacing when needed.

Look for causes such as myocardial ischemia or infarction, hypoxia, medication or toxin effects—including beta-blockers, calcium-channel blockers, or digoxin—and electrolyte abnormalities. Correcting the cause is part of treatment.

Tachycardia and instability

Tachyarrhythmia is commonly at least $150$ per minute, but rate alone does not establish the need for emergency treatment. Assess whether the rhythm is causing hypotension, acutely altered mental status, shock, ischemic chest discomfort, or acute heart failure.

Initial support includes maintaining the airway, assisting breathing as needed, giving oxygen if the patient is hypoxemic, monitoring rhythm, blood pressure, and oxygen saturation, obtaining IV access, and getting a $12$-lead ECG when available.

Unstable tachyarrhythmia

If persistent tachyarrhythmia is causing cardiopulmonary compromise, perform Synchronized cardioversion. Sedate whenever feasible without delaying urgent treatment. Use the device-recommended energy setting; if it is unknown, use the maximum setting. Reassess the rhythm and patient after each attempt. If cardioversion fails, consider the underlying cause, increasing energy, an antiarrhythmic drug, and expert consultation.

For polymorphic VT, synchronization may not be reliable, so deliver an unsynchronized high-energy shock (defibrillation). If the patient loses a pulse, switch immediately to the cardiac-arrest algorithm.

Stable tachycardia by rhythm

For stable tachyarrhythmia, determine whether the rhythm is regular or irregular and narrow- or wide-complex. A Wide QRS is at least $0.12$ seconds. Obtain expert consultation when diagnosis or treatment is uncertain.

• Regular, narrow-complex: consider vagal maneuvers and adenosine. Give an initial adenosine dose of $6\ \text{mg}$ as a rapid IV push followed by a flush; if needed, give $12\ \text{mg}$. A beta-blocker or calcium-channel blocker may be considered when appropriate.

• Wide-complex: consider an antiarrhythmic infusion and expert consultation. Adenosine may be considered only for a stable, regular, monomorphic wide-complex rhythm when the cause is uncertain. Do not give adenosine for an unstable, irregularly irregular, or polymorphic wide-complex rhythm. Avoid verapamil and diltiazem in wide-complex tachycardia.

For stable wide-complex tachycardia, AHA algorithm options include:

• Procainamide: give $20\text{–}50\ \text{mg/min}$ until the rhythm is suppressed, hypotension occurs, QRS duration increases by more than $50\%$, or a maximum of $17\ \text{mg/kg}$ is reached. Maintenance is $1\text{–}4\ \text{mg/min}$. Avoid procainamide with prolonged QT or heart failure.

• Amiodarone: give $150\ \text{mg}$ IV over $10$ minutes; repeat if VT recurs, followed by $1\ \text{mg/min}$ for the first $6$ hours.

Drug choice and use require clinical expertise and attention to contraindications.

Pathway recap and reassessment

Reassess the patient and rhythm after every intervention, and promptly change pathways if pulse status or rhythm changes.

• No pulse: begin CPR first. Shock VF/pVT, but do not shock PEA/asystole. Give epinephrine during resuscitation and treat reversible causes.

• Bradycardia with compromise: support airway, breathing, and circulation; give atropine; if it is ineffective, use pacing and/or an epinephrine or dopamine infusion while addressing the cause.

• Tachycardia with compromise: use synchronized cardioversion, except that polymorphic VT requires an unsynchronized shock. For stable tachycardia, use QRS width and regularity to guide treatment.

• shockable rhythm