Introduction:
Laryngospasm is a life-threatening complication during the perioperative period with various causes and severe consequences.
Pathophysiology:
Laryngospasm is a complex physiological response involving the upper airway and the body’s reflex mechanisms. It occurs when the vocal cords in the larynx suddenly close, obstructing the flow of air into the trachea and lungs. This reflexive closure of the vocal cords is the body’s attempt to protect the lower airways from the entry of foreign substances, such as liquids or particulate matter. Laryngospasm can occur during the perioperative period, typically during intubation or extubation, and can be life-threatening.
The pathophysiology of laryngospasm involves several key elements:
- Triggering Factors:
Laryngospasm can be triggered by various factors, which can be classified into three main categories:
- Mechanical Factors: These include physical manipulation or irritation of the airway, such as contact with an endotracheal tube during intubation.
- Chemical Factors: Exposure to irritants, such as gastric contents, blood, or foreign substances, can lead to laryngospasm.
- Thermal Factors: Extreme changes in temperature or exposure to hot or cold substances can stimulate the laryngeal reflex.
- Afferent Nerve Pathways:
When one of the triggering factors is encountered, afferent nerve fibers in the upper airway are activated. These afferent fibers are primarily associated with the superior laryngeal nerve, a branch of the vagus nerve (cranial nerve X). The superior laryngeal nerve carries sensory information from the larynx to the brain, serving as the afferent pathway in the reflex. - Receptor Activation:
These afferent fibers terminate in specialized receptors known as laryngeal mucosal receptors that are distributed along the glottis, which is the space between the vocal cords in the larynx. These receptors are sensitive to a wide range of stimuli, including mechanical touch, chemical irritants, and temperature changes. - Signal Transmission to Brainstem:
Sensory information from the superior laryngeal nerve is transmitted to the brainstem, specifically to the solitary tract nucleus. This nucleus plays a crucial role in the control and coordination of various reflexes, including upper airway reflexes. The solitary tract nucleus serves as the processing center for incoming signals. - Efferent Nerve Pathways:
Upon processing in the brainstem, efferent nerve signals are sent out to orchestrate the response. The recurrent laryngeal nerve, another branch of the vagus nerve, plays a central role in the efferent pathway. It innervates the muscles responsible for vocal cord adduction, i.e., the lateral cricoarytenoid muscles, thyroarytenoid muscles, and cricothyroid muscles. - Muscles Responsible for Vocal Cord Adduction:
Laryngospasm involves the adduction of the vocal cords, where they come together, closing the glottis. This adduction is primarily achieved by the action of the mentioned muscles. Their coordinated contraction results in the forceful closure of the glottis, leading to laryngospasm.
Risk Factors:
Laryngospasm risk factors can be categorized into patient-related, surgery-related, and anesthesia-related factors.
| Patient-Related | Surgery-Related | Anesthesia-Related |
|---|---|---|
| – Obesity | – Nasal, oral, or pharyngeal | – Extubation |
| – Smoking | surgeries | – Blood/secretions in |
| – Young age | – GI endoscopy | the airway |
| – Gastroesophageal | – Bronchoscopy | – Regurgitation |
| reflux | – Anal or cervical | – Desflurane |
| – Obstructive sleep | dilatation | – Ketamine and |
| apnea | – Appendectomy | thiopental induction |
| – Hypocalcemia | – Mediastinoscopy | – Nasogastric tube |
| – Asthma | – Inferior urologic surgery | – Inexperience of |
| – Difficult airway | – Surgical stimulus | anesthesiologist |
| – Recurrent laryngeal | – Laryngoscopy | |
| nerve damage | – Failed intubation | |
| – Esophageal | ||
| stimulation |
Diagnosis:
Laryngospasm diagnosis is based on clinical signs and symptoms, including inspiratory stridor, paradoxical respiratory movements, and decreasing oxygen saturation.
Dangers of Laryngospasm and Consequences:
| Dangers and Consequences | Incidence (%) |
|---|---|
| – Bradycardia | 6% |
| – Negative Pressure Pulmonary Edema | 4% |
| – Cardiac Arrest | 0.5% |
| – Pulmonary Aspiration | 3% |
| – Arrhythmias | Varies |
| – Death | Varies |
Management:
Laryngospasm management involves a structured approach:
| Step | Actions |
|---|---|
| 1. Identification and Removal | – Identify and remove the triggering stimulus. |
| 2. Call for Help and Delegate | – Call for assistance and delegate tasks to the team. |
| 3. Assess Airway Entry | – Assess the airway entry and determine the extent of laryngospasm. |
| 4. Gentle Maneuvers | – Attempt gentle maneuvers to break the spasm: lifting the chin, jaw thrust, temporomandibular subluxation, etc. |
| 5. Deepen Anesthesia | – Administer propofol (usually less than 0.8mg/kg) to deepen anesthesia. |
| 6. Muscle Relaxants | – Consider muscle relaxants such as succinylcholine (usually 0.1mg/kg IV) to break the spasm. |
| 7. Thoracic Pressure or Larson’s | – Apply gentle thoracic pressure or perform Larson’s Maneuver to induce pain and potentially relax the vocal cords. |
| 8. Intubation or Surgical | – If laryngospasm persists, consider orotracheal intubation, cricothyroidotomy, or tracheostomy as a last resort. |
Follow-Up:
Patients who experience laryngospasm should be closely observed in the recovery ward for 2-3 hours to ensure a clear airway and exclude complications such as pulmonary aspiration and post-obstructive pulmonary edema.
In conclusion, laryngospasm is a critical perioperative complication with various risk factors and severe consequences. Understanding and addressing these factors, along with prompt and systematic management, are essential for patient safety.
