Laryngospasm & Aspiration

Larynx innervated by CN X (vagus) via two branches:

Recurrent Laryngeal Nerve (RLN) - Sensory: glottis and below (subglottic mucosa) - Motor: ALL intrinsic muscles of the larynx except the cricothyroid

Superior Laryngeal Nerve (SLN) - Internal branch: sensory above the cords (epiglottis, supraglottic mucosa) - External branch: motor to the cricothyroid muscle (adductor — tenses cords)

Bilateral RLN injury → unopposed SLN activity → vocal cord adduction → airway obstruction (the "anatomic emergency" after thyroidectomy).

Definition: closure of the true vocal cords (± false cords) from sustained laryngeal muscle contraction. Mediated by the SLN.

Predisposing factors: - Stage 2 of anesthesia (excitement / delirium) - Light anesthesia relative to stimulation - Mechanical irritants: blood, mucus, vomit, secretions - Airway device irritation: ETT (RR 12) > LMA (RR 7) > facemask - Suctioning - Reactive airway: asthma, eczema, smoking exposure - Recent URI (within 1 month) — RR 3.4 - Pediatrics ~3× more likely than adults

Detection: - Inspiratory stridor or silent airway - ↑ inspiratory effort, tracheal tug, paradoxical chest/abdominal movement - Poor EtCO₂ tracing, desaturation, bradycardia, central cyanosis

1. Jaw thrust + head tilt + oral/nasal airway
2. - Larson's maneuver: jaw thrust with bilateral pressure on the body of the mandible anterior to the mastoid process ("laryngospasm notch")
3. Suction oropharynx
4. CPAP via bag-mask, 100% O₂ — may need pressure ~40 mmHg
5. Deepen anesthesia: propofol bolus; consider IV lidocaine 1–2 mg/kg
6. Succinylcholine 10–20 mg IV (or 4 mg/kg IM if no IV) — maintain airway with bag-mask or ETT until spontaneous breathing returns
7. Reintubate vs prepare for surgical airway
8. Monitor for NPPE

Incidence: ~0.1% of anesthetics.

Causes: - Laryngospasm - Upper airway obstruction (ETT biting, neck flexion)

Risk factors: young (20–40), healthy (ASA I–II), male (80%).

Presentation: - Frothy, serosanguinous airway secretions - ↓ SpO₂, ↓ EtCO₂, hypotension, large A-a gradient - CXR with pulmonary edema

Pathogenesis: - Negative intrathoracic pressure (up to −100 cmH₂O) - ↑ RV preload, ↑ pulmonary hydrostatic pressure - Septum shift → LV diastolic dysfunction → ↑ PCWP - Hypoxia/hypercarbia/acidosis → HPV and ↑ PVR - Stress response → ↑ SVR / afterload - Alveolar-capillary stress failure

Treatment: supportive — PEEP, diuresis if needed, often self-limited within 24 h.

Risk factors: - NPO violations - Full stomach (trauma, recent meal) - GERD, gastroparesis (DM, autonomic neuropathy) - Pregnancy (after ~20 weeks) - Bowel obstruction, ileus - ↑ ICP, neurologic disease - Opioids - Diabetes (gastroparesis) - Difficult airway with prolonged mask ventilation

ASA NPO guidelines: | Substance | Hours | |---|---| | Clear liquids | 2 | | Breast milk | 4 | | Infant formula | 6 | | Light meal | 6 | | Fatty meal | 8 |

Prevention: - Follow NPO guidelines - H2 blockers, metoclopramide, non-particulate antacid (Bicitra) - RSI for full stomach - Cricoid pressure (controversial) - Awake intubation when high risk

Management of suspected aspiration: 1. Tilt head down/lateral; suction airway 2. Intubate to protect airway 3. Bronchoscopy if particulate matter 4. Lung-protective ventilation; PEEP 5. Do NOT routinely give steroids or prophylactic antibiotics — reserved for bacterial superinfection 6. Monitor for ARDS; CXR may lag 24 h