9.1 PALS Resuscitation Algorithms & Cardiac Arrest Pharmacotherapy

9.1 PALS Resuscitation Algorithms & Cardiac Arrest Pharmacotherapy

Pediatric cardiopulmonary arrest is physiologically distinct from adult sudden cardiac arrest. While adult cardiac arrest is predominantly secondary to primary ischemic ventricular dysrhythmias, pediatric arrest is overwhelmingly the terminal consequence of progressive tissue hypoxia and respiratory failure or uncompensated circulatory shock. Over 70% to 80% of pediatric arrests present initially with non-shockable rhythms—specifically asystole or pulseless electrical activity (PEA). Consequently, successful resuscitation depends on the immediate restoration of oxygen delivery, high-quality chest compressions, early vasopressor administration, and systematic identification of reversible underlying causes.

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High-Quality CPR & Resuscitation Metrics

Cardiopulmonary resuscitation (CPR) must be initiated immediately upon recognizing cardiac arrest (unresponsiveness, absent breathing or only gasping, and no central pulse detected within 10 seconds). The quality of CPR directly dictates coronary perfusion pressure (CPP) and cerebral blood flow.

Essential CPR Quality Benchmarks

• Compression Rate: 100 to 120 compressions per minute.
• Compression Depth: At least one-third the anterior-posterior (AP) diameter of the chest:
  • Infants (<1 year): Approximately 1.5 inches (4 cm).
  • Children (1 year to puberty): Approximately 2 inches (5 cm).
  • Adolescents: 2 to 2.4 inches (5 to 6 cm).
• Chest Recoil: Allow complete chest wall recoil between compressions; leaning on the chest elevates intrathoracic pressure, blunts venous return, and severely reduces coronary perfusion pressure.
• Compression-to-Ventilation Ratio:
  • Single Rescuer: 30:2 compressions-to-ventilations.
  • Two Healthcare Rescuers: 15:2 compressions-to-ventilations.
  • With Advanced Airway (ETT / Supraglottic): Continuous chest compressions without pauses for ventilations; deliver 1 breath every 2 to 3 seconds (20 to 30 breaths/min).
• Minimize Interruptions: Keep pauses in compressions to <10 seconds (e.g., during rhythm analysis and defibrillation charging).
• Avoid Hyperventilation: Excessive ventilation increases intrathoracic pressure, compresses the vena cava and pulmonary vascular bed, decreases cardiac output, and induces cerebral vasoconstriction via acute hypocapnia ($PaCO_2 < 35 \text{ mmHg}$).

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Shockable Rhythms: VF & Pulseless VT Algorithm

Ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT) represent approximately 15% to 20% of pediatric in-hospital cardiac arrests (and up to 25% of sudden out-of-hospital collapses in older children and adolescents). The primary therapeutic intervention is rapid, unsynchronized electrical defibrillation.

Shockable Cardiac Arrest Flow (VF / Pulseless VT):

[Recognize VF/pVT] ──► [Shock 1: 2 J/kg] ──► [Immediate CPR x 2 min]
                                                        │
                                     [Rhythm Check: Persistent VF/pVT]
                                                        │
                                                        ▼
                                            [Shock 2: 4 J/kg]
                                                        │
                                                        ▼
                                             [Immediate CPR x 2 min]
                                             - Epinephrine 0.01 mg/kg IV/IO
                                             - Repeat Epinephrine q3-5 min
                                                        │
                                     [Rhythm Check: Persistent VF/pVT]
                                                        │
                                                        ▼
                                      [Shock 3: >=4 J/kg (max 10 J/kg)]
                                                        │
                                                        ▼
                                             [Immediate CPR x 2 min]
                                             - Amiodarone 5 mg/kg IV/IO
                                               OR Lidocaine 1 mg/kg IV/IO

Defibrillation Dosing Sequence

1. First Shock: 2 J/kg (biphasic or monophasic).
2. Second Shock: 4 J/kg.
3. Subsequent Shocks: $\ge 4 \text{ J/kg}$ (titrated up to 10 J/kg or the adult maximum biphasic dose of 200 J [or 360 J monophasic]).
4. Critical Rule: Immediately resume high-quality CPR for 2 minutes following every shock without pausing to check rhythm or pulse.

Resuscitation Pharmacotherapy for Shockable Arrest

• Epinephrine:
  • Timing: Administer during CPR following the second shock (Cycle 2).
  • Dose: 0.01 mg/kg IV/IO (0.1 mL/kg of 0.1 mg/mL [1:10,000] solution; maximum single dose: 1 mg / 10 mL).
  • Frequency: Repeat every 3 to 5 minutes throughout the arrest.
• Antiarrhythmic Selection (Refractory VF/pVT):
  • Indicated for persistent VF or pulseless VT refractory to CPR, defibrillation, and vasopressor therapy (administered after the third shock).
  • Amiodarone:
    • Dose: 5 mg/kg IV/IO rapid bolus (maximum single dose: 300 mg).
    • Repetition: May repeat the 5 mg/kg bolus twice for refractory VF/pVT (cumulative maximum dose: 15 mg/kg or 450 mg per 24 hours).
    • Formulation Note: Amiodarone contains polysorbate 80 and benzyl alcohol, which cause peripheral vasodilation and myocardial depression in perfusing rhythms; however, in pulseless cardiac arrest, it is administered as a rapid IV/IO push.
  • Lidocaine:
    • Loading Dose: 1 mg/kg IV/IO bolus (maximum: 100 mg).
    • Maintenance Infusion: If ROSC is achieved, initiate a continuous infusion at 20 to 50 mcg/kg/min (0.02 to 0.05 mg/kg/min) to prevent recurrence of malignant ventricular arrhythmias.
  • Clinical Evidence: The ROC-ALPS and multicenter pediatric resuscitation studies demonstrated equivalent rates of ROSC and survival to hospital discharge between amiodarone and lidocaine. Lidocaine is frequently preferred due to easier preparation and fewer drug-drug interactions.

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Non-Shockable Rhythms: Asystole & PEA Algorithm

Pulseless electrical activity (PEA) and asystole constitute the vast majority of pediatric cardiac arrests. Because electrical defibrillation has no efficacy in non-shockable rhythms, survival depends entirely on uninterrupted CPR, rapid vasopressor administration, and identifying the underlying trigger.

Immediate Priorities

1. Initiate High-Quality CPR: Provide continuous chest compressions and ventilations with 100% oxygen.
2. Immediate Epinephrine Administration:
   • In non-shockable rhythms, epinephrine must be administered as soon as vascular access (IV or IO) is obtained.
   • Dosing: 0.01 mg/kg IV/IO (0.1 mL/kg of 0.1 mg/mL [1:10,000]; maximum single dose: 1 mg), repeated every 3 to 5 minutes.
   • Time-to-Epinephrine Criticality: Large observational pediatric cohorts confirm that every 1-minute delay in epinephrine administration beyond 5 minutes from arrest onset leads to a step-wise decline in ROSC, survival to discharge, and favorable neurological outcome.
3. Search for Reversible Etiologies: Actively investigate and correct reversible causes throughout the resuscitation.

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Vascular Access & Routes of Drug Delivery

Endotracheal Drug Dosing Mandates

• Epinephrine ET Dose: 0.1 mg/kg (0.1 mL/kg of the concentrated 1 mg/mL [1:1,000] formulation).
  • The 10-Fold Rule: The endotracheal dose of epinephrine is 10 times higher than the standard IV/IO dose ($0.1 \text{ mg/kg}$ vs $0.01 \text{ mg/kg}$).
  • Technique: Dilute in 1 to 5 mL of 0.9% normal saline, instill directly into the endotracheal tube (past the tip using a catheter), and follow with 5 rapid positive-pressure ventilations to disperse the medication into the distal alveolar bed.
• Contraindicated ET Drugs: Sodium bicarbonate and calcium salts must NEVER be administered via the endotracheal tube; they cause acute chemical alveolitis, mucosal sloughing, and surfactant deactivation.

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Reversible Causes of Pediatric Arrest: The H's and T's

Reversible Causes (H's & T's) Differential Matrix:

        [Hypovolemia]        ──► 20 mL/kg balanced crystalloid / blood
        [Hypoxia]            ──► 100% FiO2, bag-mask / endotracheal intubation
        [Hydrogen Ion (Acid)]──► Sodium bicarbonate 1 mEq/kg (if documented)
  H's   [Hypoglycemia]       ──► D10W 5-10 mL/kg (neonates/infants) or D25W 2-4 mL/kg
        [Hypo/Hyperkalemia]  ──► Ca-gluconate/chloride, insulin+dextrose, albuterol
        [Hypothermia]        ──► Active internal/external rewarming

        [Tension Pneumothorax] ──► Needle thoracostomy (2nd ICS MCL or 4th/5th AAL)
        [Tamponade (Cardiac)]  ──► Emergent pericardiocentesis
  T's   [Toxins / Overdose]    ──► Naloxone, lipid emulsion, specific antidotes
        [Thrombosis (Pulm/PE)] ──► Thrombolytics (Alteplase 0.1-0.6 mg/kg) / ECMO
        [Thrombosis (Coronary)]──► Percutaneous intervention / anticoagulation

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Post-Resuscitation Care & Targeted Temperature Management (TTM)

Following Return of Spontaneous Circulation (ROSC), patients enter the post-cardiac arrest syndrome phase, characterized by brain injury, myocardial dysfunction, systemic ischemia-reperfusion response, and persistent precipitating pathology.

Targeted Temperature Management (TTM) Protocols

Brain injury is the leading cause of mortality and long-term morbidity after pediatric cardiac arrest. Post-ROSC fever markedly increases cerebral metabolic rate ($CMRO_2$) by approximately 6% to 8% per $1^\circ\text{C}$ rise, uncoupling oxygen supply and demand, promoting free radical release, and exacerbating neuronal apoptosis.

• Target Temperature Range:
  • Induced Therapeutic Hypothermia: Maintain core temperature between $32^\circ\text{C}$ and $34^\circ\text{C}$ for 48 hours, followed by controlled slow rewarming at a rate of $0.25^\circ\text{C}$ to $0.5^\circ\text{C}$ per hour.
  • Actively Controlled Normothermia: Maintain core temperature between $36^\circ\text{C}$ and $37.5^\circ\text{C}$ for 72 hours.
  • The THAPCA Trials (Therapeutic Hypothermia After Pediatric Cardiac Arrest): Randomized multi-center clinical trials in both in-hospital (THAPCA-IH) and out-of-hospital (THAPCA-OH) pediatric cardiac arrest demonstrated equivalent 1-year survival with favorable neurobehavioral outcomes between hypothermia (32–34°C) and controlled normothermia (36–37.5°C).
  • BCPPS Clinical Rule: Both hypothermia (32–34°C) and normothermia (36–37.5°C) are acceptable guidelines-endorsed options; however, active prevention and aggressive treatment of fever ($T \ge 38^\circ\text{C}$) is universally mandatory.

Hemodynamic, Respiratory & Neurological Goals Post-ROSC

• Blood Pressure Optimization: Maintain systolic and mean arterial pressure (MAP) at least above the 50th percentile for age (or $>5\text{th}$ percentile threshold at minimum) using continuous vasoactive infusions (epinephrine or norepinephrine) to ensure adequate cerebral perfusion pressure ($CPP = MAP - ICP$).
• Oxygenation Strategy: Titrate inspired oxygen ($FiO_2$) to maintain oxyhemoglobin saturation between 94% and 99%. Strictly avoid hyperoxia ($PaO_2 > 300 \text{ mmHg}$), which accelerates reactive oxygen species (ROS) formation and reperfusion tissue injury. Avoid hypoxia ($SpO_2 < 94%$).
• Ventilation Strategy: Target normocapnia ($PaCO_2 \text{ 35 to 45 mmHg}$). Prevent hypocapnia ($PaCO_2 < 35 \text{ mmHg}$), which triggers cerebral vasoconstriction and worsens ischemic brain injury. Prevent severe hypercapnia, which increases intracranial pressure ($ICP$).
• Glucose Control: Target blood glucose 80 to 180 mg/dL. Prevent hypoglycemia (exacerbates brain death) and treat severe hyperglycemia with titrated regular insulin infusions.
• Electroencephalography (EEG): Continuous EEG monitoring is recommended for at least 24 to 48 hours post-ROSC; non-convulsive status epilepticus occurs in 10% to 40% of comatose pediatric survivors and requires aggressive anticonvulsant management (levetiracetam, fosphenytoin, midazolam infusions).