Bronchospasm and laryngospasms for 10 marks

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Here is a complete 10-mark answer on Bronchospasm and Laryngospasm based on the textbook content retrieved:

Bronchospasm and Laryngospasm

LARYNGOSPASM

Definition

Laryngospasm is a forceful, involuntary reflex closure of the laryngeal inlet (true vocal cords, false cords, and aryepiglottic folds) causing partial or complete airway obstruction. It is potentially life-threatening if not recognized and treated promptly.

Mechanism

Stimulation of the laryngeal mucosa (by secretions, blood, or irritants) excites the internal branch of the Superior Laryngeal Nerve (SLN) (afferent limb - vagus nerve), triggering contraction of:

Lateral cricoarytenoid muscle - adduction and medial rotation of arytenoid cartilage
Thyroarytenoid muscle - shortening of vocal cords → glottic closure (via recurrent laryngeal nerve)
Cricothyroid muscle - tensing of vocal cords (via external branch of SLN)

Repetitive suprathreshold stimulation leads to persistent adductor motor output (true laryngeal spasm) that continues beyond the cessation of the stimulus.

Incidence

Overall: ~0.79% of all anesthetics
Children: 1-25% (higher risk); most common in infants 1-3 months old
Adults: ~1 in 250 anesthetics

Types

Complete laryngospasm - total glottic closure; no air movement; resists PPV up to 140 mmHg
Incomplete laryngospasm - partial closure; some air movement with significant effort; inspiratory stridor present

Clinical Features

Inspiratory stridor
Suprasternal and supraclavicular retractions
Paradoxical chest movements ("rocking" - chest sinks as abdomen rises)
Loss of capnography waveform
No reservoir bag movement
Progressive SpO2 desaturation → bradycardia → cardiac arrest

Risk Factors

Patient factors: Recent upper respiratory tract infection (URI), asthma/atopy, eczema, airway anomalies, passive smoke exposure, younger age

Anesthetic factors: Light plane of anesthesia, volatile anesthetic use, secretions or blood in airway, airway manipulation, multiple intubation attempts, inexperienced provider

Surgical factors: High airway stimulation - tonsillectomy, adenoidectomy, airway surgery

Time of Occurrence

Most common at induction and emergence (the "critical" intervals). Extubation during the interval between "deep" and "awake" is most hazardous.

Treatment

Step-wise approach:

Remove the stimulus (suction secretions/blood)
100% O2 by well-fitted mask + CPAP of 15-20 cm H2O
Jaw thrust (Larson's maneuver - pressure at the "laryngospasm notch" between the mastoid, angle of mandible, and base of skull)
Deepen anesthesia - IV propofol (1-2 mg/kg) or IV lidocaine (1-1.5 mg/kg)
If above fails → Succinylcholine (IV: 0.5-1 mg/kg; IM: 4-6 mg/kg if no IV access) + atropine, followed by controlled ventilation
Alternatively: Rocuronium 0.4 mg/kg IV

Note: Aggressive PPV alone should NOT be relied upon for complete laryngospasm - it may cause gastric distension, aspiration, and decreased FRC.

BRONCHOSPASM

Definition

Bronchospasm is the excessive contraction of bronchial smooth muscle causing narrowing of airways. In the perioperative setting it manifests as acute-onset wheezing, increased airway resistance and decreased compliance.

Incidence

~9% of asthmatics develop perioperative bronchospasm
~25% of asthmatics may wheeze after induction of anesthesia
Can occur in non-asthmatics - only 50% of bronchospasm cases have prior asthma/COPD history
~40 ASA Closed Claims cases; 88% resulted in brain damage or death

Causes / Triggers

Airway manipulation in lightly anesthetized patient (most common)
Endotracheal intubation - direct tracheal stimulation
Endobronchial intubation
Airway foreign body or mucus plug
Pulmonary aspiration
Anaphylaxis (bronchospasm may be the first sign)
Histamine-releasing drugs (morphine, atracurium, thiopentone)
Recent URI, active asthma, COPD, heavy smokers

Clinical Features / Diagnosis

Wheezing on auscultation (expiratory > inspiratory)
Decreased lung compliance (increased PIP on volume-controlled ventilation)
Changes in ventilator flow-volume loops (obstructive pattern)
Changes in capnogram (sloped plateau, "shark fin" waveform)
SpO2 desaturation
Paradoxical movement of chest/abdomen
Differential diagnosis: endobronchial intubation, kinked ETT, ETT cuff occlusion, mucus plug, aspiration, anaphylaxis

Prevention

Thorough preoperative evaluation; optimize asthma preoperatively
Avoid airway manipulation at light planes of anesthesia
Use bronchodilating agents for induction: propofol or ketamine (avoid barbiturates, etomidate)
Avoid histamine-releasing drugs
Maintenance with volatile anesthetics (sevoflurane > isoflurane > desflurane as bronchodilators); avoid desflurane in reactive airways
Preoperative nebulization with salbutamol in high-risk patients

Treatment

Step	Intervention
1	Deepen anesthesia - increase volatile agent (sevoflurane preferred) or give IV propofol
2	Inhaled salbutamol (albuterol) - 4-8 puffs via ETT or nebulization
3	IV salbutamol or aminophylline (if severe)
4	IV hydrocortisone 100-200 mg (or methylprednisolone)
5	Adrenaline (epinephrine) IV/IM if anaphylaxis suspected
6	Ketamine IV (1-2 mg/kg) - direct bronchodilator via catecholamine release
7	Magnesium sulfate 1.2-2 g IV - adjunct bronchodilator

Specific pharmacological interventions:

Propofol/Ketamine - for induction/deepening
Sevoflurane - most potent volatile bronchodilator; relaxes airway smooth muscle via VDC channel inhibition
Avoid desflurane (increases airway resistance, especially in children with reactive airways)

KEY COMPARISON TABLE

Feature	Laryngospasm	Bronchospasm
Site	Glottis / supraglottic	Lower airways (bronchi/bronchioles)
Mechanism	Reflex adductor muscle spasm via SLN	Smooth muscle contraction of bronchi
Stridor	Inspiratory stridor (classic)	Expiratory wheeze (classic)
Most common time	Induction and emergence	Induction and maintenance
First-line drug	Propofol, succinylcholine	Inhaled salbutamol, deepen anesthesia
Key emergency drug	Succinylcholine	Adrenaline (if anaphylaxis) / salbutamol
Risk in children	Very high (1-25%)	Higher with atopy/asthma
Complication	Hypoxia, negative pressure pulmonary edema, cardiac arrest	Hypoxia, hypercarbia, barotrauma

Sources: Miller's Anesthesia 10e; Barash Clinical Anesthesia 9e; Morgan & Mikhail's Clinical Anesthesiology 7e; Cummings Otolaryngology

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