16.1 Pediatric Assessment Triangle (PAT), Common Emergencies & Pediatric Dosing

16.1 Pediatric Assessment Triangle (PAT), Common Emergencies & Pediatric Dosing

The Pediatric Assessment Triangle (PAT): Observational Rapid Triage

Pediatric patients pose unique clinical challenges in prehospital medicine. Anatomical, physiological, and developmental differences prevent the direct extrapolation of adult assessment heuristics to infants and children. Under the Canadian Paramedic Competence Framework (CPCF Appendix A #13, #32), primary care paramedics must rapidly establish clinical acuity before initiating physical contact. Approaching a sick child with a cold stethoscope, blood pressure cuff, or penlight frequently provokes crying, agitation, and physiological resistance, obscuring baseline vital signs and precipitating acute airway collapse in vulnerable patients.

The Pediatric Assessment Triangle (PAT) is a validated, visual-auditory assessment tool executed in 15 to 30 seconds from across the room ("the doorway assessment"). Without placing hands on the patient, the paramedic evaluates three discrete physiological components:

1. Appearance: Reflects central nervous system (CNS) function, cerebral oxygenation, cerebral perfusion, and metabolic homeostasis.
2. Work of Breathing: Reflects airway resistance, respiratory mechanics, muscular effort, and alveolar oxygenation.
3. Circulation to Skin: Reflects cardiac output, systemic vascular resistance, and core-to-peripheral microvascular perfusion.

                    [Appearance]
                   (CNS Status)
                       /    \
                      /      \
                     /        \
  [Work of Breathing] ──────── [Circulation to Skin]
 (Airway & Mechanics)           (Cardiovascular Perfusion)

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The TICLS Mnemonic: Deconstructing Appearance

Appearance is the single most sensitive indicator of pediatric physiological status. Because young children cannot verbalize nuanced symptoms, subtle changes in neurological alertness and behavioral engagement serve as early heralds of critical illness. Paramedics assess Appearance using the TICLS mnemonic:

• Tone: Does the infant move vigorously, resist passive extension, and maintain normal muscle tone? Flaccidity, limpness, hypotonia, or rigid posturing indicates severe CNS depression, profound hypoxia, or severe acidemia.
• Interactiveness: Does the child attend to environmental sounds, follow colorful objects, reach for toys, or engage with parents? A child who ignores parent presence, shows no curiosity, or fails to interact with familiar stimuli exhibits an altered mental status.
• Consolability: Does the crying infant settle when held, rocked, or spoken to by a primary caregiver? Inconsolable, persistent crying despite parental soothing suggests acute distress, meningeal irritation, severe pain, or severe systemic hypoxemia. Paradoxical irritability—where the infant cries harder when held and quietens when left untouched—is a classic indicator of meningitis or peritonitis.
• Look / Gaze: Does the child maintain direct eye contact and track family members, or is their gaze blank, vacant, glassy, or fixed on the ceiling? An "empty" or wandering gaze signifies severe encephalopathy, post-ictal states, or impending cerebral hypoperfusion.
• Speech / Cry: Is the vocalization a strong, lusty, vigorous cry or clear, age-appropriate verbal speech? A weak, muffled, hoarse, high-pitched, or absent cry indicates laryngeal obstruction, severe neuromuscular fatigue, or profound central depression.

PAT Diagnostic Categorization Matrix

By synthesizing the findings across the three arms of the triangle, the paramedic assigns the patient to an actionable physiological category:

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Upper Airway Emergencies: Croup vs. Acute Epiglottitis

Upper airway obstruction in pediatrics is life-threatening due to unique pediatric anatomy: a funnel-shaped larynx with the narrowest portion at the cricoid cartilage (subglottic space), a large occiput causing neck flexion in supine positioning, a relatively massive tongue, and small airway diameters. Poiseuille's Law dictates that airway resistance is inversely proportional to the fourth power of the airway radius ($R \propto 1/r^4$). In an infant, 1 mm of circumferential mucosal edema reduces the airway cross-sectional area by up to 75% and increases airway resistance sixteen-fold.

Paramedics must rapidly differentiate between viral croup and bacterial epiglottitis:

Prehospital Management Protocols

Croup (Laryngotracheobronchitis)

1. Minimize Agitation: Keep the child calm on the parent's lap. Agitation increases turbulent air velocity through the narrowed subglottic segment, worsening airway collapse.
2. Humidified Blow-By Oxygen: Provide cool, humidified oxygen or blow-by oxygen via tubing held near the face by a parent.
3. Nebulized Epinephrine (1:1,000 / 1 mg/mL): Indicated for moderate-to-severe croup with stridor at rest, marked indrawing, or agitation. Administer 5 mL of undiluted epinephrine 1:1,000 (5 mg) via jet nebulizer with 6–8 L/min oxygen flow. The alpha-1 adrenergic effect causes rapid subglottic mucosal vasoconstriction, dramatically reducing edema within 10 to 30 minutes. Paramedics must monitor for rebound swelling after 1 to 2 hours.
4. Corticosteroids: Administer dexamethasone 0.6 mg/kg orally (PO), intramuscularly (IM), or intravenously (IV) (maximum single dose 16 mg) to reduce mucosal inflammation and prevent symptom recurrence.

Acute Epiglottitis

[!CAUTION] Strict Contraindication: No Oral Inspection or Agitation: Paramedics must NEVER use a tongue depressor, penlight, or suction catheter to inspect the posterior pharynx of a child with suspected epiglottitis. Any mechanical stimulation or acute panic can trigger reflex laryngospasm and complete, fatal airway occlusion. Avoid IV attempts, blood pressure cuffs, or separating the child from the parent on scene.

1. Position of Comfort: Permit the child to maintain their self-selected upright tripod or sniffing position on the parent's lap.
2. Passive High-Concentration Oxygen: Provide high-flow blow-by oxygen held gently 2 to 5 cm from the child's face by the parent.
3. Rapid Transport & Pre-Arrival Notification: Transport immediately with minimal sirens. Transmit an urgent pre-arrival alert to the emergency department to assemble an airway team (anesthesiology and otolaryngology/ENT) for controlled operating room intubation.

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Progression of Pediatric Respiratory Failure

Pediatric respiratory arrest is the leading cause of secondary cardiac arrest in children. Recognizing the transition from compensatory distress to decompensated failure is paramount:

[Respiratory Distress]
   Tachypnea, Nasal Flaring, Retractions, Normal CNS, Physiologic Grunting
       │
       ▼ (Muscle Fatigue & Hypercapnia)
[Respiratory Failure]
   Head Bobbing, Seesaw Breathing, Lethargy, Inattention, Bradypnea
       │
       ▼ (Profound Hypoxia & Acidosis)
[Respiratory Arrest / Cardiopulmonary Collapse]
   Severe Bradycardia, Agonal Respirations / Apnea, Flaccidity, Asystole

Clinical Markers of Respiratory Distress vs. Failure

• Tachypnea: The earliest physiological compensatory response to hypoxemia and hypercapnia.
• Retractions: Inward drawing of the chest wall during inspiration, categorized by anatomical location: subcostal, substernal, intercostal, and supraclavicular/sternal indrawing (reflecting increasing negative intrathoracic pressures).
• Nasal Flaring: Reflex dilatation of the anterior nares to reduce upper airway resistance.
• Head Bobbing: Seen in infants who recruit the sternocleidomastoid and scalene muscles; the head flexes forward during inspiration and extends during exhalation.
• Grunting: Exhalation against a partially closed glottis. Grunting increases end-expiratory pressure, functioning as physiologic PEEP (Positive End-Expiratory Pressure) to prevent terminal bronchiolar and alveolar atelectasis. Hearing grunting indicates severe alveolar disease (e.g., pneumonia, pulmonary edema) or severe systemic acidosis.
• Seesaw (Paradoxical) Breathing: The chest falls as the abdomen expands during inspiration, signaling diaphragmatic exhaustion and imminent ventilatory collapse.
• The Silent Chest: Complete absence of wheezing or stridor in an exhausted, struggling child. This does not indicate clinical improvement; it signifies that air movement is so minimal that audible turbulence can no longer be generated.
• Bradycardia: In a pediatric patient with respiratory distress or failure, bradycardia is an ominous, pre-terminal sign of severe tissue hypoxia. Immediate positive-pressure ventilation with 100% oxygen via Bag-Valve-Mask (BVM) is mandatory. If heart rate drops below 60 bpm despite effective ventilation, CPR must begin immediately.

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Weight-Based Resuscitation & Length Tape Calibration

Pediatric drug doses, fluid aliquots, and airway equipment sizes are determined by weight in kilograms, never estimated haphazardly. In high-stress prehospital resuscitations, cognitive calculation errors multiply five- to ten-fold without standardized tools.

Length-Based Resuscitation Tapes (Broselow / Handtevy)

• Operating Principle: The length-based tape links body length directly to estimated weight (in kilograms) and predetermined color zones.
• Application Technique ("Red to Head"): Place the tape flat alongside the supine child. Align the red end of the tape precisely with the crown of the child's head. Extend the tape down the longitudinal body axis to the heel. The color zone aligned with the infant's flat heel establishes the weight bracket, corresponding drug dosages, defibrillation energy levels, and airway equipment sizes.
• Handtevy Pediatric System: Integrates length with age-based dosing guidelines (e.g., 1, 3, 5, 7, 9 years corresponds to 10, 15, 20, 25, 30 kg), standardizing 1 mL volume equivalents for core emergency medications to eliminate complex decimal calculations in the field.

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Pediatric Hemodynamics: Compensated vs. Hypotensive Shock

Pediatric cardiovascular physiology is distinct from adults:

• Fixed Stroke Volume: Pediatric myocardial fibers are non-compliant and immature. The pediatric ventricle cannot augment stroke volume significantly via Frank-Starling mechanics. Cardiac output is almost entirely rate-dependent ($\text{Cardiac Output} = \text{Heart Rate} \times \text{Stroke Volume}$). Therefore, sinus tachycardia is the primary, earliest compensatory mechanism for hypovolemia, hypoxia, and shock.
• Compensated Shock: Children possess vigorous peripheral vasoconstrictive capacity. By constricting peripheral and splanchnic vascular beds, a pediatric patient can maintain a normal systolic blood pressure despite losing 25% to 30% of circulating blood volume. Signs of compensated shock include tachycardia, delayed capillary refill (>2 seconds), cool and pale extremities, weak peripheral pulses, and tachypnea, all while systolic blood pressure remains normal.
• Hypotensive (Decompensated) Shock: When compensatory mechanisms exhaust, cardiac output collapses precipitously. Hypotension is a late, catastrophic finding in pediatrics, immediately preceding cardiopulmonary arrest.

Age-Specific Pediatric Vital Signs & Blood Pressure Thresholds

Pediatric Fluid Resuscitation Protocols

1. Fluid Type: Isotonic crystalloid solution (0.9% Normal Saline or Lactated Ringer's). Never administer hypotonic fluids or dextrose-containing solutions for acute volume expansion.
2. Bolus Volume: Administer 10 to 20 mL/kg intravenously (IV) or intraosseously (IO). For a 15 kg child, a 20 mL/kg bolus equals 300 mL.
3. Administration Speed: Infuse rapidly over 5 to 20 minutes using a three-way stopcock push-pull system or pressure bag. Rapid gravity drip through a pediatric cannula is too slow to treat hypovolemic shock.
4. Mandatory Cardiopulmonary Reassessment: Following each bolus, re-evaluate:
   • Signs of improvement: Decreased heart rate, normalized capillary refill (≤2 seconds), warming extremities, clearing mental status, rising blood pressure.
   • Signs of fluid overload: Bilateral pulmonary crackles, tachypnea, hepatomegaly (palpate liver margin below the right costal margin). If signs of fluid overload develop, halt fluid infusions immediately.
   • In children with cardiogenic shock, myocarditis, or severe closed head injury, start with conservative fluid aliquots of 5 to 10 mL/kg.

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Clinical Scenario: Decompensating Pediatric Respiratory Distress

Paramedics are dispatched to a rural residence for an 18-month-old male with "trouble breathing."

1. Observational Triage (PAT):
   • Appearance: The child is sitting on the mother's lap, lethargic, with glassy eyes, weak whines, and poor motor tone (TICLS abnormal).
   • Work of Breathing: Marked inspiratory stridor at rest, pronounced sternal and subcostal indrawing, and prominent head bobbing (abnormal).
   • Circulation: Skin is pale and mottled with perioral pallor (abnormal).
   • Classification: Cardiopulmonary Failure / Exhausted Respiratory Failure with high risk of immediate arrest.
2. Initial Intervention: Paramedic 1 calmly holds high-flow oxygen blow-by tubing next to the mother's hand while Paramedic 2 prepares nebulized epinephrine 1:1,000 (5 mL) via jet mask. The crew avoids separating the child or attempting venipuncture on scene.
3. Length-Based Sizing: The paramedic unrolls the Broselow tape: the child measures in the purple zone (10 kg). Airway sizing (4.0 cuffed ETT, size 1.5 LMA, size 1 Miller blade) and medication doses are confirmed instantly.
4. Pharmacotherapy: The child receives 5 mL of 1:1,000 epinephrine via nebulizer and oral dexamethasone (6 mg in suspension) swallowed with mother's help. En route, the stridor softens, retractions diminish from severe to moderate, and the child makes eye contact with the paramedic (PAT shifts to Respiratory Distress). Paramedics alert the receiving trauma center for priority pediatric handover.

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Exam Pitfalls & High-Yield Pediatric Pearls

• Agitating a Suspected Epiglottitis Patient: Never use a tongue depressor or attempt invasive procedures on scene with a child in the tripod position with drooling and high fever. Agitation triggers fatal laryngospasm.
• Waiting for Hypotension to Diagnose Shock: A normal blood pressure does not rule out shock in a child. Children maintain blood pressure via profound vasoconstriction until 25% to 30% of blood volume is lost. Tachycardia and delayed capillary refill are the true indicators of shock.
• Treating Bradycardia as Primary Cardiac Pathology: Pediatric bradycardia in the setting of respiratory distress is secondary to severe hypoxemia. The primary intervention is positive-pressure ventilation with 100% oxygen, not atropine.
• Calculating Medications Manually Under Stress: Always use a length-based resuscitation tape (Broselow / Handtevy) to prevent catastrophic ten-fold dosing errors.
• Using Adult Dosing Guidelines for Pediatric Fluids: Always calculate fluid boluses precisely at 10 to 20 mL/kg of isotonic crystalloids; never free-hang open IV lines on pediatrics without volumetric buretrols or infusion pumps.