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ACLS Protocol 

3 min read

Background  #

I) Definition 

Advanced Cardiac Life Support (ACLS) is a set of clinical interventions and algorithms for the urgent treatment of cardiac arrest, stroke, and other life-threatening cardiovascular emergencies. It builds upon Basic Life Support (BLS) with the addition of advanced airway management, rhythm recognition, intravenous access, drug administration, and treatment of reversible causes. ACLS protocols are standardized by the American Heart Association (AHA) and are designed to improve survival and neurological outcomes following cardiac arrest. 

II) Classification/Types 

By Cardiac Arrest Rhythm: 

  • Shockable Rhythms: 
    • Ventricular Fibrillation (VF) 
    • Pulseless Ventricular Tachycardia (VT) 
  • Non-shockable Rhythms: 
    • Pulseless Electrical Activity (PEA) 
    • Asystole 

By Clinical Setting: 

  • In-Hospital Cardiac Arrest (IHCA) 
  • Out-of-Hospital Cardiac Arrest (OHCA) 

By Intervention Phase: 

  • Immediate Response (Recognition, CPR, Defibrillation) 
  • Advanced Resuscitation (Airway, IV access, drugs) 
  • Post-Cardiac Arrest Care (Targeted temperature management, hemodynamics, neurologic support) 

Pathophysiology 

Cardiac arrest interrupts perfusion to vital organs, especially the brain and heart. Immediate CPR provides partial circulatory support, while defibrillation restores organized electrical activity in shockable rhythms. ACLS medications like epinephrine increase coronary and cerebral perfusion pressure. The pathophysiologic rationale behind ACLS includes stabilizing myocardial membrane potentials, restoring effective cardiac rhythm, and reversing metabolic or mechanical causes (Hs & Ts). 

Epidemiology 

  • Approximately 356,000 out-of-hospital cardiac arrests occur annually in the U.S., with a survival to discharge of 10–12%. 
  • In-hospital cardiac arrests affect 1–5 per 1,000 admissions, with higher survival (~25%). 
  • Early bystander CPR and prompt defibrillation double or triple survival chances. 
  • Use of structured ACLS protocols correlates with improved outcomes in cardiac arrest resuscitation. 

Etiology  #

I) Causes 

Cardiac Causes: 

  • Acute myocardial infarction 
  • Cardiomyopathies 
  • Primary arrhythmias (e.g., long QT, Brugada) 
  • Valvular heart disease 
  • Myocarditis 

Non-Cardiac Causes (Hs & Ts): 

  • Hypovolemia 
  • Hypoxia 
  • Hydrogen ion (acidosis) 
  • Hypo-/hyperkalemia 
  • Hypothermia 
  • Tension pneumothorax 
  • Tamponade (cardiac) 
  • Toxins (e.g., drugs, poisons) 
  • Thrombosis (coronary or pulmonary) 
  • Trauma 

II) Risk Factors 

  • History of coronary artery disease or heart failure 
  • Low left ventricular ejection fraction 
  • Male sex, advanced age 
  • Previous arrhythmic events or ICD shocks 
  • Poorly controlled comorbidities (e.g., diabetes, hypertension) 

Clinical Presentation  #

I) History (Symptoms) 

  • Sudden collapse or unresponsiveness 
  • Possible preceding symptoms: chest pain, palpitations, dyspnea, syncope 
  • Witnessed cardiac arrest improves chances of survival 

II) Physical Exam (Signs) 

  • Unresponsiveness, absence of pulse, apnea 
  • Cyanosis or agonal gasping 
  • May show signs of trauma, drug use, or medical ID indicating underlying illness 

Differential Diagnosis (DDx)  #

  • Seizure or vasovagal syncope 
  • Respiratory arrest without cardiac arrest 
  • Hypoglycemia 
  • Stroke or intracranial hemorrhage 
  • Pulmonary embolism 

Diagnostic Tests  #

Initial Work-Up (During Resuscitation) 

  • ECG: Rhythm diagnosis (VF, VT, asystole, PEA) 
  • Capnography: ETCO₂ <10 mmHg suggests inadequate CPR 
  • POCUS: May identify tamponade, pneumothorax, cardiac standstill 
  • Labs: Electrolytes, ABG, glucose, cardiac enzymes, toxicology 

Advanced Testing (Post-ROSC) 

  • Echocardiography 
  • Coronary angiography 
  • Cardiac MRI 
  • Neurologic imaging if indicated 
  • Genetic testing in young or unexplained arrests 

Treatment  #

I) Acute Management (ACLS Protocol Highlights) 

1. Immediate Actions: 

  • Start high-quality CPR (rate 100–120/min, depth 2–2.4 inches) 
  • Attach monitor/defibrillator 
  • Deliver shock if VF/VT (defibrillate at 200J biphasic) 
  • Resume CPR immediately after shock 

2. Medications: 

  • Epinephrine 1 mg IV/IO every 3–5 minutes (all rhythms) 
  • Amiodarone (300 mg IV bolus, then 150 mg if needed) for VF/pVT 
  • Consider lidocaine as alternative 

3. Airway & Oxygenation: 

  • Provide bag-valve-mask ventilation with 100% oxygen 
  • Advanced airway (ET tube or supraglottic) if CPR quality can be maintained 

4. Identify and Treat Reversible Causes (Hs & Ts) 

5. Monitor CPR quality and rhythm every 2 minutes 

II) Chronic/Post-Resuscitation Management 

  • Hemodynamic and respiratory stabilization in ICU 
  • Targeted Temperature Management (32–36°C for 24 hours) 
  • Identify underlying cause: ECG, cath, echo 
  • Neurological evaluation 
  • Preventive interventions: ICD for survivors with structural heart disease 

Medications 

Drug Class Examples Notes 
Vasopressors Epinephrine 1 mg IV/IO every 3–5 min during arrest 
Antiarrhythmics Amiodarone, Lidocaine For refractory VF/pVT 
Electrolyte therapy Mg++, K+, Ca++ Correct deficits or toxicity 
Sedation/Post-ROSC Midazolam, Propofol Used after ROSC and during TTM 

Device Therapy 

  • Defibrillator: Essential for shockable rhythms 
  • Advanced airway: ET tube or supraglottic if prolonged resuscitation 
  • ICD: For secondary prevention post-arrest 
  • ECMO or VAD: In refractory cardiogenic shock or during ECPR protocols 

Patient Education, Screening, Vaccines  #

  • CPR training for family or caregivers 
  • Education on warning signs: syncope, palpitations 
  • Genetic counseling for inherited arrhythmia syndromes 
  • Lifestyle modification (smoking cessation, diet, exercise) 
  • Vaccination (influenza, pneumococcus) for chronic cardiac patients 

Consults/Referrals  #

  • Cardiology: Post-arrest management, revascularization 
  • Electrophysiology: ICD placement, rhythm evaluation 
  • Critical Care: ICU and targeted temperature management 
  • Neurology: Post-resuscitation assessment 
  • Psychology: Address anxiety, PTSD in survivors 

Follow-Up  #

Short-Term 

  • In-hospital monitoring for recurrent arrhythmia 
  • Neurologic recovery and functional status 
  • Optimization of heart failure or ischemic therapy 

Long-Term 

  • Regular ICD check-ups 
  • Cardiac rehabilitation 
  • Genetic screening for relatives if inherited cause suspected 
  • Support groups and mental health counseling 

Prognosis 

  • Survival to discharge: 
    • Out-of-hospital: ~10–12% 
    • In-hospital: up to 25% 
  • Better outcomes: 
    • Witnessed arrest 
    • Prompt CPR and defibrillation 
    • Reversible cause 
    • Short downtime and preserved neurologic function 

Updated on November 16, 2025