16.2 Procedural Sedation & Rapid Sequence Intubation in Children

16.2 Procedural Sedation & Rapid Sequence Intubation in Children

Procedural sedation and rapid sequence intubation (RSI) are critical clinical competencies in pediatric acute care, emergency medicine, and intensive care units. Pediatric airway anatomy differs substantially from that of adults: children possess a relatively large occiput (causing neck flexion when supine), a large tongue relative to the oral cavity, a cephalad and anterior larynx ($C3\text{--}C4$ vs $C5\text{--}C6$ in adults), a floppy, omega-shaped epiglottis, and a narrowest airway diameter at the cricoid cartilage (subglottic funnel shape) rather than the vocal cords. Furthermore, high metabolic oxygen consumption ($6\text{--}8 \text{ mL/kg/min}$ in infants vs $2\text{--}3 \text{ mL/kg/min}$ in adults) and low functional residual capacity (FRC) lead to rapid hemoglobin desaturation during apnea. This section details the continuum of procedural sedation, pre-sedation fasting standards, pharmacologic sedatives, and evidence-based protocols for pediatric RSI.

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The ASA Continuum of Sedation

The American Society of Anesthesiologists (ASA) and American Academy of Pediatrics (AAP) define sedation as a dynamic continuum ranging from minimal sedation to general anesthesia. Because pediatric patients frequently transition unpredictably between depth levels, clinicians administering procedural sedation must be credentialed and equipped to rescue a patient who enters a depth deeper than intended.

The ASA Continuum of Sedation Depth:

[Minimal Sedation]      ──► Normal response to verbal stimulation; airway/ventilation unaffected
        │
        ▼
[Moderate Sedation]     ──► Purposeful response to verbal/tactile stimulation; airway patent;
(Conscious Sedation)        spontaneous ventilation adequate; CV function maintained
        │
        ▼
[Deep Sedation]         ──► Purposeful response only to repeated/painful stimulation;
                            airway intervention often required; ventilation may be inadequate
        │
        ▼
[General Anesthesia]    ──► Unarousable even with painful stimulus; airway intervention mandatory;
                            spontaneous ventilation impaired; cardiovascular function may be impaired

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Pre-Sedation Fasting (NPO) Guidelines

To prevent pulmonary aspiration of gastric contents during sedation-induced depression of protective laryngeal reflexes, elective procedural sedation adheres to the ASA "2-4-6-8" fasting rule.

ASA Pre-Sedation Fasting Rules (Elective Procedures):

[Clear Liquids]          ──► Minimum 2 Hours  (Water, Fruit Juices without Pulp, Pedialyte)
[Human Breast Milk]      ──► Minimum 4 Hours  (Empties faster than bovine formula)
[Infant Formula]         ──► Minimum 6 Hours  (Bovine/Soy protein requires prolonged digestion)
[Non-Human Milk / Light] ──► Minimum 6 Hours  (Toast and clear liquids; light non-fatty meal)
[Fatty / Fried / Meat]   ──► Minimum 8 Hours  (Significantly delays gastric emptying half-time)

Fasting Exceptions in Urgent and Emergent Clinical Scenarios

In pediatric emergencies (e.g., irreducible incarcerated hernia, open fracture, severe traumatic injury, acute respiratory distress), the risk of delaying urgent intervention frequently outweighs the potential risk of pulmonary aspiration. In non-fasted urgent cases, the clinician must:

1. Choose procedural agents that preserve protective pharyngeal and laryngeal reflexes (e.g., ketamine).
2. Minimize sedation depth to the lowest effective level.
3. Prepare suction equipment, bag-valve-mask, and age-appropriate advanced airway supplies at the bedside.

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Pharmacologic Agents for Procedural Sedation

Selecting procedural sedatives requires balancing desired depth, analgesia requirements, hemodynamic stability, and recovery kinetics.

Procedural Sedation Agent Comparison Matrix:

┌───────────────┬──────────────┬─────────────┬─────────────────┬───────────────────────────────┐
│ Drug Agent    │ Analgesic?   │ Airway Drive│ Hemodynamics    │ Key Adverse Effects & Pearls  │
├───────────────┼──────────────┼─────────────┼─────────────────┼───────────────────────────────┤
│ Ketamine      │ YES (Potent) │ PRESERVED   │ Stable / ↑ HR/BP│ Emergence delirium, salivation│
│ Propofol      │ NO           │ DEPRESSED   │ Hypotension     │ Apnea, PRIS (prolonged inf)   │
│ Dexmedetomidine│ Mild         │ PRESERVED   │ Bradycardia, ↓BP│ Slow onset (10–15 min), safe  │
│ Midazolam     │ NO           │ Mild-Mod ↓  │ Minimal change  │ Paradoxical agitation (1–5%)  │
│ Fentanyl      │ YES (Potent) │ DEPRESSED   │ Minimal change  │ Chest wall rigidity (rapid IV)│
└───────────────┴──────────────┴─────────────┴─────────────────┴───────────────────────────────┘

1. Ketamine Hydrochloride

Ketamine is a phencyclidine derivative that functions as an uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, inhibiting thalamocortical pathways while stimulating the limbic system. This produces a unique state of dissociative anesthesia characterized by profound somatic analgesia, amnesia, cataleptic immobility, and functional dissociation from the environment.

• Dosing:
  • Intravenous (IV): 1 to 2 mg/kg IV bolus over 1 to 2 minutes (titrate additional 0.5–1 mg/kg increments q10–15 min as needed).
  • Intramuscular (IM): 3 to 4 mg/kg IM (preferred for combative uncooperative children without IV access; duration 30–60 minutes).
• Airway & Respiration: Ketamine is exceptional among parenteral anesthetics because it preserves protective airway reflexes and spontaneous ventilatory drive. It possesses direct bronchial smooth muscle relaxing properties via sympathomimetic release of endogenous catecholamines, making it the ideal procedural sedative and induction agent for patients with severe acute asthma exacerbations.
• Adverse Effects & Clinical Pearls:
  • Hypersalivation & Bronchorrhea: Stimulation of salivary and bronchial secretions can trigger laryngospasm. Pre-treatment or co-administration with an anticholinergic agent—glycopyrrolate (0.005 to 0.01 mg/kg IV; max 0.2 mg) or atropine (0.02 mg/kg IV; min 0.1 mg, max 0.5 mg)—effectively blunts hypersecretion.
  • Emergence Delirium & Hallucinations: Occurs in 5% to 15% of children, particularly adolescents and older children (rare in infants <2 years). Manifests as vivid dreams, agitation, confusion, and hallucinations upon recovery. Can be prevented or treated with small doses of midazolam (0.05 mg/kg IV).
  • Laryngospasm: Transient laryngospasm occurs in <0.5% of cases; managed with gentle positive-pressure bag-valve-mask ventilation with 100% $O_2$; refractory cases require succinylcholine.
  • Intracranial & Intraocular Pressure (ICP/IOP): Historically considered contraindicated in head trauma; recent literature demonstrates that when ventilation and oxygenation are rigorously maintained, ketamine does not adversely elevate ICP and preserves cerebral perfusion pressure ($CPP$).

2. Propofol (Diprivan)

Propofol is an ultra-short-acting alkylphenol derivative that facilitates central inhibitory neurotransmission through direct activation of gamma-aminobutyric acid type A ($GABA_A$) receptors and inhibition of NMDA receptors.

• Dosing: 1 to 2 mg/kg IV slow loading dose over 2 to 3 minutes, followed by intermittent boluses of 0.5 to 1 mg/kg every 3 to 5 minutes, or a continuous micro-infusion of 50 to 150 mcg/kg/min for procedural imaging (e.g., MRI/CT).
• Pharmacodynamics: Extremely rapid onset (30 to 45 seconds) and rapid recovery (5 to 10 minutes) with clear cognitive emergence and intrinsic antiemetic properties. Provides zero analgesia; must be combined with an opioid or regional block if the procedure is painful.
• Adverse Effects & Safety Mandates:
  • Dose-Dependent Hypotension: Blunts sympathetic vascular tone and directly depresses myocardial contractility, causing substantial decreases in mean arterial pressure (MAP). Avoid in hypovolemia or decompensated shock.
  • Respiratory Depression & Apnea: Transient central apnea occurs in up to 30% of patients following rapid bolus delivery.
  • Propofol Infusion Syndrome (PRIS): Prolonged continuous infusion of propofol is strictly contraindicated in pediatric intensive care. Infusions exceeding 4 mg/kg/hour (approx >67 mcg/kg/min) for >48 hours impair mitochondrial fatty acid oxidation and oxidative phosphorylation, precipitating refractory metabolic acidosis, severe hypertriglyceridemia, rhabdomyolysis, hepatomegaly, acute renal failure, and fatal bradyarrhythmic cardiovascular collapse.

3. Dexmedetomidine (Precedex)

Dexmedetomidine is an imidazole derivative that functions as an ultra-selective alpha-2 adrenergic receptor agonist (8-fold higher selectivity for alpha-2 over alpha-1 compared to clonidine). It acts centrally in the locus coeruleus to induce non-REM sleep-like sedation.

• Dosing: Loading dose of 0.5 to 1 mcg/kg IV infused over 10 minutes, followed by a maintenance continuous infusion of 0.2 to 1.4 mcg/kg/hour.
• Clinical Virtues: Produces unique "cooperative sedation" wherein the pediatric patient is calm and sedated but can be easily awakened to follow commands. Crucially preserves spontaneous respiratory drive and upper airway patency, making it ideal for non-invasive diagnostic procedures (MRI, auditory brainstem response testing) and non-intubated pediatric patients with difficult airways.
• Hemodynamic Monitoring: Rapid intravenous boluses can stimulate peripheral vascular alpha-2B receptors, causing transient vasoconstriction and hypertension. This is rapidly followed by central sympatholysis, producing dose-dependent sinus bradycardia and systemic hypotension. Atropine or glycopyrrolate should be immediately accessible.

4. Midazolam & Fentanyl Combination

• Midazolam (0.05 to 0.1 mg/kg IV; max 2 mg single dose): Short-acting benzodiazepine delivering anxiolysis and anterograde amnesia. Paradoxical agitation occurs in 1% to 5% of young children.
• Synergistic Hazard: Combining midazolam with fentanyl (1 to 2 mcg/kg IV) produces synergistic sedation and analgesia, but also synergistic central hypoventilation, airway collapse, and apnea. Continuous monitoring with capnography is mandatory.

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Pediatric Rapid Sequence Intubation (RSI)

Rapid sequence intubation is the virtually simultaneous administration of a potent induction agent and a fast-acting neuromuscular blocking agent (NMBA) to facilitate rapid endotracheal intubation while minimizing the risk of pulmonary aspiration in a patient with a presumed full stomach.

The Standard "Seven Ps" of Pediatric RSI Timeline:

[Zero - 10 min]  ──► 1. PREPARATION     (Equipment, Weight calculation, SOAP ME checklist)
[Zero - 5 min]   ──► 2. PREOXYGENATION  (100% FiO2 via non-rebreather; maintain FRC)
[Zero - 3 min]   ──► 3. PRETREATMENT    (Atropine 0.02 mg/kg in infants <1 yr; Lidocaine)
[Zero]           ──► 4. PARALYSIS WITH INDUCTION (Etomidate/Ketamine THEN Succinylcholine/Roc)
[Zero + 30 sec]  ──► 5. PROTECTION & POSITIONING (External laryngeal manipulation; ramp)
[Zero + 45-60 s] ──► 6. PLACEMENT WITH PROOF     (Direct/video laryngoscopy, Colorimetric/EtCO2)
[Post-Tube]      ──► 7. POST-INTUBATION MGMT     (Secure tube, sedation infusion, chest X-ray)

1. Pretreatment & Premedication: Atropine

• The Vagal Reflex: Infants and children under 1 year of age have immature sympathetic innervation and heightened parasympathetic (vagal) tone. Mechanical stimulation of the pharynx and larynx during direct laryngoscopy triggers profound, acute reflex bradycardia. Furthermore, succinylcholine stimulates parasympathetic cardiac muscarinic ($M_2$) receptors, compounding bradyarrhythmias and potentially triggering asystole.
• Dosing Parameters:
  • Atropine Sulfate: 0.02 mg/kg IV administered 2 to 3 minutes prior to induction.
  • Minimum Absolute Dose: 0.1 mg IV (doses <0.1 mg stimulate presynaptic muscarinic autoreceptors, causing paradoxical worsening of bradycardia).
  • Maximum Single Dose: 0.5 mg in children, 1.0 mg in adolescents.
• Mandatory Indications:
  1. All infants <1 year of age undergoing RSI.
  2. All children <5 years of age receiving succinylcholine.
  3. Any child receiving a second dose of succinylcholine.

2. Induction Agents for RSI

• Etomidate (0.3 mg/kg IV):
  • Imidazole derivative; onset 15–30 seconds; duration 5–15 minutes.
  • Virtues: Remarkable hemodynamic stability; does not cause hypotension or depress myocardial performance.
  • Adverse Effect: Transient, reversible inhibition of 11-beta-hydroxylase, the rate-limiting enzyme in adrenal cortisol and aldosterone synthesis. A single induction dose can cause biochemical adrenal suppression for 24 to 48 hours. Use with caution in septic shock.
• Ketamine (1 to 2 mg/kg IV):
  • Hemodynamically robust; preserves mean arterial pressure via endogenous catecholamine surge.
  • First-line induction agent for pediatric septic shock, anaphylaxis, and acute status asthmaticus.
• Propofol (1.5 to 3 mg/kg IV):
  • Rapid onset (15–30 sec); preferred induction agent in status epilepticus or traumatic brain injury without shock.
  • Avoid in hemodynamic instability or volume depletion.

3. Neuromuscular Blocking Agents (NMBAs)

RSI Neuromuscular Blocker Comparison: Succinylcholine vs Rocuronium:

┌────────────────────────────┬─────────────────────────────┬─────────────────────────────────┐
│ Parameter                  │ Succinylcholine             │ Rocuronium                      │
├────────────────────────────┼─────────────────────────────┼─────────────────────────────────┤
│ Class                      │ Depolarizing NMBA           │ Non-Depolarizing Aminosteroid   │
│ Standard RSI Dose          │ 1–2 mg/kg IV (3–4 mg/kg IM) │ 1.0–1.2 mg/kg IV                │
│ Onset of Paralysis         │ 30 to 45 seconds            │ 45 to 60 seconds                │
│ Duration of Clinical Block │ 4 to 10 minutes             │ 30 to 60 minutes                │
│ Metabolism / Reversal      │ Plasma Pseudocholinesterase │ Sugammadex (2, 4, or 16 mg/kg)  │
│ Critical Safety Hazards    │ Hyperkalemia, Malignant HTN │ Prolonged paralysis if airway lost│
└────────────────────────────┴─────────────────────────────┴─────────────────────────────────┘

A. Succinylcholine Chloride (Depolarizing)

• Dosing: 1 to 2 mg/kg IV in older children; 2 to 3 mg/kg IV in infants <1 year (or 3 to 4 mg/kg IM) due to the expanded volume of extracellular fluid distribution.
• Onset & Duration: Onset within 30 to 45 seconds; duration of action is brief (4 to 10 minutes), metabolized rapidly by circulating plasma pseudocholinesterase (butyrylcholinesterase).
• Black Box Warning & Contraindications:

  [!CAUTION] FDA Black Box Warning: Risk of Acute Rhabdomyolysis and Fatal Hyperkalemic Cardiac Arrest. Succinylcholine is strictly contraindicated in children with skeletal muscle myopathies (such as Duchenne or Becker muscular dystrophy), personal or family history of malignant hyperthermia, major crush injuries or extensive third-degree burns >24 to 48 hours old, severe denervation states (spinal cord injury), and baseline pre-existing hyperkalemia. In undiagnosed muscular dystrophy (frequently unapparent in boys <8 years), sustained motor end-plate depolarization precipitates massive intracellular potassium leakage, ventricular fibrillation, and cardiac arrest refractory to conventional resuscitation.

• Malignant Hyperthermia Trigger: Succinylcholine triggers uncontrolled sarcoplasmic reticulum calcium release via mutant ryanodine ($RYR1$) receptors. Treatment requires immediate cessation of triggering agents, hyperventilation with 100% $O_2$, cooling, and administration of intravenous dantrolene (2.5 mg/kg IV initial bolus, repeated up to 10 mg/kg).

B. Rocuronium Bromide (Non-Depolarizing)

• Dosing for RSI: 1.0 to 1.2 mg/kg IV.
  • Clinical Pearl: The standard intubation dose of rocuronium is 0.6 mg/kg (onset 90–120 seconds). To match the ultra-rapid 45-to-60-second onset of succinylcholine for RSI, the dose must be escalated to 1.0 to 1.2 mg/kg IV.
• Duration: Prolonged duration of clinical neuromuscular blockade (30 to 60+ minutes).
• Reversal with Sugammadex (Bridion):
  • Modified gamma-cyclodextrin that selectively binds and encapsulates free aminosteroid molecules (rocuronium > vecuronium) in plasma at a 1:1 molar ratio, creating an inert, water-soluble complex eliminated unchanged by the kidneys.
  • Routine Reversal (Moderate Block, 2 twitches on train-of-four [TOF]): 2 mg/kg IV.
  • Deep Neuromuscular Blockade (1 to 2 post-tetanic counts [PTC], 0 twitches on TOF): 4 mg/kg IV.
  • Immediate Emergency Rescue Reversal ("Cannot Intubate, Cannot Ventilate" scenario, administered ~3 minutes post-rocuronium 1.2 mg/kg): 16 mg/kg IV single bolus (rapidly restores spontaneous diaphragmatic ventilation and train-of-four recovery within 1.5 to 3 minutes).

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Practice Pearls & BCPPS Exam Traps

• Exam Trap 1 (Atropine Premedication Minimum): Never administer an atropine dose less than 0.1 mg IV, even if a strict 0.02 mg/kg calculation for a neonate yields 0.04 mg. Doses below 0.1 mg trigger central or presynaptic muscarinic autoreceptor-mediated paradoxical bradycardia.
• Exam Trap 2 (Ketamine in Status Asthmaticus): When choosing an induction agent for a child with respiratory failure secondary to status asthmaticus, select ketamine (1–2 mg/kg IV) due to its potent bronchial smooth muscle relaxation; avoid propofol if hemodynamically unstable.
• Exam Trap 3 (Succinylcholine in Pediatrics): Avoid succinylcholine for routine elective RSI in young pediatric males due to the risk of undiagnosed Duchenne muscular dystrophy. If a question presents a boy with acute flaccid paralysis, crush injury >48 hours, or myopathy, succinylcholine is absolutely contraindicated; the correct answer is rocuronium.
• Exam Trap 4 (Rocuronium RSI Dose): Do not use 0.6 mg/kg of rocuronium for rapid sequence intubation. 0.6 mg/kg requires 90 to 120 seconds for optimal intubating conditions; true rapid sequence intubation demands 1.0 to 1.2 mg/kg IV.