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Basic Life Support (BLS)

BLS Algorithm (Adult Cardiac Arrest)

Steps:

1. Verify scene safety
2. Check responsiveness — shout, stimulate
3. Activate emergency response — call 911, get AED
4. Assess pulse + breathing simultaneously (<10 seconds)
   • Normal breathing, pulse felt → Monitor
   • No breathing, pulse felt → Rescue breaths (1 breath every 6 sec; give naloxone if opioid OD suspected)
   • No breathing, no pulse → Start CPR
5. CPR: 30 compressions : 2 breaths; use AED as soon as available
6. AED arrives → Check rhythm → shock if shockable; resume CPR immediately for 2 min

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Quality CPR Parameters

Discontinuation of BLS

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Advanced Cardiac Life Support (ACLS)

ACLS Algorithm (Adult Cardiac Arrest)

Shockable rhythms (VF / pulseless VT):

1. Shock → CPR 2 min + IV/IO access
2. If still shockable: Shock → CPR 2 min + Epinephrine q3–5 min ± advanced airway
3. If still shockable: Shock → CPR 2 min + Amiodarone + treat reversible causes (H's & T's)

Non-shockable rhythms (Asystole / PEA):

1. CPR 2 min + IV/IO access + Epinephrine q3–5 min ± advanced airway
2. CPR 2 min + treat reversible causes
3. If rhythm becomes shockable → go to shockable arm

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Airway Management in ACLS

• Bag-Mask Ventilation (BMV) or advanced airway (ETI or SGA) are both acceptable
• When advanced airway is in place: 1 breath every 6 compressions (10/min)
• SGA preferred over ETI if operator ETI experience is limited
• Each breath: ~600 mL over 1 second

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Key ACLS Medications

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Reversible Causes — The H's & T's

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Monitoring During ACLS

• End-tidal CO₂ (EtCO₂): Normal ~35–45 mmHg; optimal CPR yields 15–20 mmHg; ROSC → sudden rise to >35 mmHg. EtCO₂ <10 mmHg after >20 min of resuscitation = marker of futility
• Arterial BP, oximetry, and bedside ultrasound also used

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Post-Cardiac Arrest Care (ROSC)

• Target MAP ≥65 mmHg or SBP ≥90 mmHg (fluids + pressors)
• Target SpO₂ 94%, PaO₂ ~100 mmHg, PaCO₂ 35–45 mmHg
• Consider emergent coronary angiography/PCI for suspected coronary occlusion
• Targeted Temperature Management (TTM)
• ICU-level neurological monitoring

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BASIC LIFE SUPPORT (BLS)

Definition and Purpose

"There should be minimal delay between diagnosis and preparatory effort in the initial response and institution of BLS." — Braunwald's Heart Disease

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The Chain of Survival (AHA Framework)

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The CAB Sequence (AHA Update)

• Compressions maintain perfusion without interruption
• Avoids excessive ventilation
• Minimizes delays to circulatory support (Braunwald's)

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Step-by-Step BLS Protocol

1. Scene Safety & Recognition

• Verify the scene is safe
• Check for responsiveness (shout, stimulate)
• Gasping respirations and brief seizure activity are common during SCA — do not mistake them for breathing or responsiveness (Harrison's)

2. Activate Emergency Response

• Call 911 (or ask bystander to call); use speaker mode
• If opioid overdose suspected → administer naloxone if available
• Check for pulse (≤10 seconds) — do not delay compressions for prolonged pulse check

3. Chest Compressions (C)

"Chest compressions generate forward cardiac output with sequential filling and emptying of the cardiac chambers, with competent valves maintaining forward direction of flow." — Harrison's Principles of Internal Medicine 22E

4. Airway (A)

• Tilt head back, lift chin; clear oropharynx of foreign bodies, dentures
• Heimlich maneuver if foreign body obstruction suspected
• In hospitals: Ambu bag ventilation until ETT placed
• Out-of-hospital: mouth-to-mouth while awaiting EMS (Braunwald's)

5. Breathing (B)

• With 30:2 ratio — deliver 2 breaths between every 30 compressions
• Each breath: ~600 mL tidal volume over 1 second
• Avoid excessive ventilation (raises intrathoracic pressure, reduces venous return)

6. Defibrillation (AED)

• Apply AED as soon as available — AED use should precede CPR check in unwitnessed arrests
• AED analyzes rhythm and advises shock for VF/pulseless VT
• Chest compressions continue while defibrillator charges
• On shock delivery: resume CPR immediately for 2 min before next rhythm check
• First shock: 200 J biphasic waveform (Harrison's)
• If shockable rhythm persists → repeat maximal energy shock every 2 min cycle

"When arrest is witnessed, use of AEDs by lay responders can improve cardiac arrest survival rates." — Harrison's 22E

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BLS Algorithm (AHA, from Fuster & Hurst's The Heart)

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Discontinuation of BLS

1. Unwitnessed arrest
2. Three CPR/AED cycles without ROSC
3. No shockable rhythm observed

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ADVANCED CARDIAC LIFE SUPPORT (ACLS)

Definition

1. Restore cardiac rhythm to one that is hemodynamically effective
2. Optimize ventilation
3. Maintain and support the restored circulation

"Implementation of ACLS is not intended to suggest an abrupt cessation of BLS activities, but rather a transition from one level of activity to the next." — Braunwald's Heart Disease

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ACLS Algorithms by Rhythm

A. Shockable Rhythms: VF / Pulseless VT

1. Chest compressions 100–120/min + immediate defibrillation (200 J biphasic) → resume CPR 2 min
2. No ROSC → 2 min CPR/ventilation + repeat shock
3. No ROSC → IV/IO access + advanced airway + Epinephrine 1 mg q3–5 min + repeat shock
4. No ROSC → Amiodarone 300 mg IV bolus (repeat 150 mg if recurs) + repeat shock
5. If amiodarone fails → Lidocaine
6. Continue guided by specific etiology (see below)

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B. Non-Shockable Rhythms: Asystole / PEA / Bradyarrhythmia

1. CPR + intubation + IV access
2. Confirm asystole (2 leads); assess pulse for PEA
3. Identify and treat reversible causes (see H's & T's below)
4. Epinephrine 1 mg IV q3–5 min
5. For bradycardia specifically:
   • Atropine 1 mg IV (note: atropine is NOT recommended for asystole/PEA per current AHA guidelines — only for bradycardic rhythms)
   • External pacing or transvenous pacing wire

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ACLS Algorithm Overview (AHA)

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Reversible Causes — The H's & T's

"Naloxone should be administered if opiate overdose is suspected." — Harrison's 22E

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Airway Management in ACLS

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ACLS Medications — Summary Table

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Monitoring During ACLS

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Post-Cardiac Arrest Care (After ROSC)

Hemodynamic Targets

• SBP >90 mmHg / MAP >65 mmHg — use vasopressors + volume as needed

Respiratory Targets

• SpO₂: 94% (avoid hyperoxia — excessive FiO₂ worsens reperfusion injury)
• PaCO₂: 35–45 mmHg (normocapnia — avoid hypo/hypercapnia)
• ETI for impaired consciousness

Coronary Angiography

• Immediate PCI if ST-elevation on post-arrest ECG
• Also consider if: cardiogenic shock, electrical instability, ongoing ischemia
• For VT/VF without ST elevation: emergent angiography not clearly superior to delayed strategy

Targeted Temperature Management (TTM)

• Brain injury due to ischemia-reperfusion is the leading cause of death post-ROSC — accounts for >2/3 of deaths (Harrison's)
• Probability of neurologic recovery decreases rapidly: <30% at 5 min from collapse to ROSC (without CPR)

Electrolyte & Metabolic Management

• Treat hyperkalemia, severe hypokalemia, QT-prolonging drug toxicity
• Monitor and correct acidosis

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Concept of Cardiocerebral Resuscitation (CCR)

• Emphasizes continuous chest compressions interrupted primarily for single shocks
• Defers and limits ventilatory actions
• Challenges the routine benefit of compression-ventilation cycling
• Adding "head-up/torso-up" positioning has been reported to nearly double resuscitation rates in community studies by improving cerebral perfusion (Braunwald's)

"Successful ROSC after IHCA is associated with a shorter median duration of resuscitation — 12 minutes (IQR 6–20 min) in survivors." — Braunwald's Heart Disease

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BLS vs. ACLS — Key Differences

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