2.2 Lower Airway Emergencies

2.2 Lower Airway Emergencies

Pediatric lower airway emergencies involve pathology located below the voice box within the bronchi, bronchioles, and pulmonary parenchyma. Because pediatric lower airways feature reduced collateral ventilation (underdeveloped Pores of Kohn and Canals of Lambert), smooth muscle hypertrophy that matures throughout early childhood, and small internal luminal diameters, inflammatory exudates, mucosal edema, and bronchospasm rapidly induce air trapping, atelectasis, and ventilation-perfusion ($\text{V}/\text{Q}$) mismatch.

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1. Bronchiolitis & Respiratory Syncytial Virus (RSV)

Pathophysiology & Epidemiology

Bronchiolitis is an acute inflammatory disease of the lower respiratory tract primarily affecting infants under 2 years of age, with peak severity occurring in infants aged 2 to 6 months. Respiratory Syncytial Virus (RSV) is responsible for 50–80% of cases, followed by human rhinovirus, human metapneumovirus, and adenovirus. The virus invades the terminal bronchiolar epithelial cells, causing necrosis, ciliary destruction, lymphocytic infiltration, and submucosal edema. Sloughed epithelial cells, dense fibrin exudate, and excessive mucus form luminal plugs, leading to partial or complete small airway obstruction, hyperinflation, and patchy atelectasis.

Clinical Presentation & Assessment

• Early Phase: 1- to 3-day upper respiratory prodrome (rhinorrhea, low-grade fever, sneezing, clear nasal discharge).
• Lower Respiratory Phase: Progressive tachypnea (respiratory rate $> 60$ breaths/min in infants), diffuse fine expiratory wheezing, mandatory intercostal/subcostal retractions, nasal flaring, prolonged expiratory phase, and coarse crackles.
• Critical Warning Signs: Infant apneas (frequently the presenting sign in premature infants or those $< 2$ months), poor feeding (due to tachypnea interfering with sucking/swallowing), lethargy, and hypoxemia ($\text{SpO}_2 < 90%$).

Evidence-Based ED Nursing Interventions

Current American Academy of Pediatrics (AAP) clinical practice guidelines emphasize supportive care:

• Airway Clearance: Standard nasal suctioning using a bulb syringe or gentle superficial suction catheter prior to feeding and sleeping. Deep nasopharyngeal suctioning is strongly discouraged as it causes mucosal trauma and rebound airway edema.
• Oxygen Therapy: Supplemental humidified oxygen via nasal cannula is indicated only if $\text{SpO}_2$ drops consistently below 90% or if severe respiratory distress is present.
• Fluid Management: Tachypnea ($> 60$ breaths/min) significantly increases insensible fluid loss and aspiration risk during oral feeding. Initiate IV isotonic fluids (0.9% Normal Saline with 5% Dextrose) or nasogastric (NG) rehydration at maintenance rates.
• Pharmacology Note: Routine administration of albuterol, epinephrine, systemic corticosteroids, and antibiotics is NOT recommended for typical bronchiolitis. High-flow nasal cannula (HFNC) therapy (1–2 L/kg/min) is indicated for moderate-to-severe respiratory distress to decrease work of breathing and provide positive end-expiratory pressure (PEEP).

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2. Pediatric Asthma Exacerbation

Pathophysiology

Pediatric asthma is a chronic inflammatory disorder of the airways characterized by hyperreactivity, bronchial smooth muscle constriction, airway mucosal edema, and mucous hypersecretion. Triggered by viral infections, allergens, cold air, or exertion, acute obstruction increases airway resistance, leading to dynamic hyperinflation (air trapping), auto-PEEP, atelectasis, hypoxemia, and eventual respiratory muscle fatigue.

Assessment & Severity Scoring

The Pediatric Respiratory Assessment Measure (PRAM) or Pediatric Asthma Severity Score (PASS) evaluates three key parameters:

1. Suprasternal Retractions: Absent (0), Mild (1), Severe (2).
2. Scalene Muscle Contraction: Absent (0), Present (2).
3. Wheezing: Absent (0), Expiratory only (1), Inspiratory and expiratory (2), Audible without stethoscope / diminished breath sounds (3).

+-----------------------------------------------------------------------------------+
|               PEDIATRIC ASTHMA EMERGENCY PHARMACOTHERAPY                          |
+-------------------+--------------------+------------------------+-----------------+
| Medication        | Dosage / Route     | Mechanism of Action    | Clinical Role   |
+-------------------+--------------------+------------------------+-----------------+
| Albuterol         | 2.5-5 mg Nebulizer | Selective Beta-2       | First-line rapid |
|                   | or 4-8 puffs MDI   | agonist; smooth muscle | bronchodilator   |
|                   | q20 min x 3        | relaxation             |                 |
+-------------------+--------------------+------------------------+-----------------+
| Ipratropium       | 250-500 mcg        | Anticholinergic;       | Synergistic with|
| Bromide           | Nebulizer x 3 doses| blocks vagal tone      | albuterol for   |
|                   | mixed with albuterol| & decreases secretions | severe attacks  |
+-------------------+--------------------+------------------------+-----------------+
| Prednisolone /    | 1-2 mg/kg PO/IV    | Anti-inflammatory;     | Reduces airway  |
| Methylprednisolone| (Max 60 mg/day)    | suppresses cytokines & | mucosal edema & |
|                   |                    | vascular permeability  | prevents relapse|
+-------------------+--------------------+------------------------+-----------------+
| Magnesium Sulfate | 25-50 mg/kg IV     | Smooth muscle relaxation| Refractory severe|
|                   | over 20 min        | via calcium channel    | status          |
|                   | (Max 2 g)          | blockade               | asthmaticus     |
+-------------------+--------------------+------------------------+-----------------+

Escalation Protocol for Severe Status Asthmaticus

When a child fails to improve after 3 continuous albuterol/ipratropium nebulizations and IV steroids:

1. IV Magnesium Sulfate: Administer 25–50 mg/kg IV (maximum 2 grams) infused over 20 minutes. Monitor blood pressure closely for hypotension.
2. Continuous Albuterol Nebulization: 10–15 mg/hour continuously.
3. Subcutaneous / IM Epinephrine or Terbutaline: Epinephrine 1:1000 (0.01 mg/kg IM/SC, max 0.3–0.5 mg) or Terbutaline (10 mcg/kg IV loading dose, followed by continuous infusion 0.4–5 mcg/kg/min).
4. Non-Invasive Ventilation / Intubation: Initiate HFNC or BiPAP. If intubation becomes mandatory, use a large ETT, allow prolonged expiratory time ($I:E$ ratio 1:3 or 1:4) to prevent air trapping and tension pneumothorax, and maintain permissive hypercapnia.

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3. Pediatric Pneumonia

Etiology & Clinical Differentiation

Pneumonia is an infection of the pulmonary parenchyma causing alveolar consolidation. The etiology varies significantly by age group:

• Neonate (< 28 days): Group B Streptococcus, Escherichia coli, Listeria monocytogenes.
• Infants & Toddlers (1 mo – 5 yrs): Viruses (RSV, Influenza, Human Metapneumovirus) are most common; Streptococcus pneumoniae is the primary bacterial cause.
• Older Children (> 5 yrs): Streptococcus pneumoniae, Mycoplasma pneumoniae, and Chlamydia pneumoniae (atypical pneumonia).

+-----------------------------------------------------------------------------------+
|               BACTERIAL VS. ATYPICAL VS. VIRAL PNEUMONIA                          |
+--------------------+-----------------------+------------------+-------------------+
| Feature            | Bacterial (S. pneumo) | Atypical (Myco)  | Viral (RSV/Flu)   |
+--------------------+-----------------------+------------------+-------------------+
| Onset              | Sudden, high fever    | Subacute, low    | Gradual prodrome  |
|                    | ($> 39^\circ\text{C}$)| grade fever      | viral upper symptoms|
+--------------------+-----------------------+------------------+-------------------+
| Cough              | Productive, painful   | Dry, hacking,    | Prominent wheezing|
|                    |                       | paroxysmal       | & crackles        |
+--------------------+-----------------------+------------------+-------------------+
| Chest Radiograph   | Lobar consolidation / | Interstitial /   | Diffuse bilateral |
|                    | pleural effusion      | bronchovascular  | streaky infiltrates|
+--------------------+-----------------------+------------------+-------------------+
| First-Line Therapy | High-dose Amoxicillin | Azithromycin     | Supportive /      |
|                    | or IV Ampicillin      |                  | Oseltamivir       |
+--------------------+-----------------------+------------------+-------------------+

Emergency Nursing Management & Antibiotic Regimens

• Outpatient Bacterial Pneumonia: High-dose oral Amoxicillin 90 mg/kg/day PO divided BID (max 4 g/day) to overcome penicillin-resistant S. pneumoniae.
• Inpatient Bacterial Pneumonia: Ampicillin 150–200 mg/kg/day IV q6h or Ceftriaxone 50–100 mg/kg/day IV q12–24h.
• Atypical Pneumonia: Azithromycin 10 mg/kg PO/IV on Day 1 (max 500 mg), followed by 5 mg/kg PO/IV once daily on Days 2–5.
• Complications: Monitor for pleural effusion and empyema (persistent fever despite 48–72 hours of appropriate antibiotics, diminished breath sounds over the base, and dullness to percussion). Empyema requires diagnostic thoracentesis or chest tube insertion with instillation of fibrinolytics (tPA).

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4. Pertussis (Whooping Cough)

Pathophysiology & Clinical Stages

Pertussis is an infection of the respiratory tract caused by the Gram-negative fastidious bacterium Bordetella pertussis. The organism attaches to ciliated respiratory epithelial cells, producing pertussis toxin and tracheal cytotoxin, which paralyze cilia, impair mucosal clearance, and induce severe inflammation and necrosis.

Pertussis progresses through three distinct clinical stages:

1. Catarrhal Stage (1–2 weeks): Insidious onset of mild upper respiratory symptoms (coryza, low-grade fever, mild cough). High contagiousness.
2. Paroxysmal Stage (2–6 weeks): Intense, uncontrollable fits of severe coughing (paroxysms) occurring 15–30 times daily. A single expiration may consist of 10–20 coughs in rapid succession, followed by a forced inspiratory effort against a narrowed glottis that creates a high-pitched "whoop." Facial petechiae, subconjunctival hemorrhages, post-tussive emesis, and post-cough cyanosis are classic.
3. Convalescent Stage (Weeks to Months): Gradual reduction in cough severity and frequency ("cough of 100 days").

Infant-Specific Nuances & Emergency Interventions

• Infants < 6 Months: Often present WITHOUT a classic whoop. Instead, coughing fits trigger sudden apnea, severe bradycardia, cyanosis, and seizure activity.
• Diagnostic Testing: Nasopharyngeal swab for B. pertussis real-time Polymerase Chain Reaction (PCR) and culture. CBC characteristically reveals marked leukocytosis with absolute lymphocytosis (WBC $> 20,000–50,000/\mu\text{L}$).
• Pharmacotherapy: Administer Azithromycin 10 mg/kg PO once daily for 5 days (in infants $< 6$ months). Macrolides eradicate B. pertussis from the nasopharynx within 5 days, rendering the patient non-contagious (otherwise contagious for 3 weeks).
• Infection Control & Public Health: Implement strict Droplet Precautions for 5 days post-antibiotic initiation. Post-exposure macrolide prophylaxis is mandatory for all close household contacts.