Laryngospasm

INTRODUCTION

Pediatric laryngospasm is the closure of the glottis caused by reflex tightening of the laryngeal muscles, leading to either partial or complete obstruction of the larynx. In a classic report, two types of laryngospasm was described: expiratory stridor, which is an active closure of the glottis secondary to adductor spasm and inspiratory stridor, which is a passive closure of the glottis secondary to a ball–valve mechanism. This condition can escalate to an anesthetic emergency when it is complete and sustained, typically occurring during the induction, maintenance, and emergence phases of general anesthesia. Symptoms of laryngospasm often include inspiratory stridor, which can progress to complete airway obstruction, increased breathing effort, tracheal tug, paradoxical breathing effort, oxygen desaturation, bradycardia, and unresponsive airway obstruction even with a Guedel airway.

INCIDENCE AND STATISTICAL DATA

The incidence of laryngospasm varies across studies, with higher occurrences in pediatric patients compared to adults. Reported rates are 0.87% in adults, 1.7% in pediatrics, and 2.82% in infants. Older children have a doubly higher incidence than adults, while younger children have a threefold higher incidence. Statistics Laryngospasm causes about 40% of postextubation airway obstruction and the incidence of complications resulting from laryngospasm can vary as follows: cardiac arrest (0.5%), obstructive negative pressure pulmonary edema (4%), pulmonary aspiration (3%), bradycardia (6%) and oxygen desaturation (61%).

RISK FACTORS

Risk factors for laryngospasm can be categorized into patient-related, surgery-related, and anesthesia-related factors;

Anesthesia-related risk factors include inadequate depth of anesthesia, which can lead to laryngospasm when stimulating events occur. Factors such as pain, movement of the cervical spine, placement of nasogastric tubes, and irritation of the vocal cords by various substances can trigger laryngospasm. Additionally, the use of muscle relaxants during tracheal intubation can lower the risk of laryngospasm. It has been observed that intravenous anesthesia is associated with a lower incidence of laryngospasm compared to inhalational anesthesia. The experience level of the anesthesiologist also plays a significant role in the occurrence of laryngospasm, with higher incidence rates reported with less experienced practitioners.

Patient-related risk factors include young age, upper respiratory infections, asthma, passive smoking, and certain medical conditions like obstructive sleep apnea and gastroesophageal reflux disease;

Surgery-related factors that increase the risk of laryngospasm include airway procedures, tonsillectomy and adenoidectomy surgeries, appendicectomy, hypospadias repair, and esophageal endoscopy.

PREVENTION

To reduce the incidence of laryngospasm, propofol induction is considered the best approach as it decreases laryngeal reflexes, especially in children with a history of asthma. Lidocaine, administered at 1-2 mg/kg intravenously two minutes before extubation, has been shown to be both preventive and corrective. Topical application of lidocaine to the vocal cords is also effective in preventing laryngospasm during general anesthesia in children. Additionally, magnesium sulfate at 15 mg/kg intravenously before tracheal extubation can reduce airway reflexes and cough, potentially preventing laryngospasm. Removing all secretions or blood from the larynx before extubation is crucial. There is ongoing debate about whether tracheal extubation should occur while patients are awake or deeply anesthetized to reduce laryngospasm. The "No touch technique" involves extubating a spontaneously breathing, awakening patient without any stimulation. The artificial cough maneuver, involving a single lung inflation with 100% oxygen immediately before tube removal, can delay/prevent desaturation and expel residual secretions, reducing vocal cord irritation.

TREATMENT

The initial step to manage laryngospasm is to remove the stimulus, followed by a firm and vigorous jaw thrust with neck and head extension, and applying CPAP with 100% oxygen via a face mask. CPAP might inflate the stomach, increasing the risk of gastric regurgitation, so some prefer moderate intermittent pressure. Despite the potential for airway devices to trigger laryngospasm, a correctly sized Guedel cannula can aid in providing CPAP.

A subhypnotic dose of propofol (0.25-0.8 mg/kg IV) usually resolves the spasm. If ineffective, succinylcholine (0.1 mg/kg IV) can be used, allowing spontaneous ventilation to continue. Rocuronium is an alternative for patients intolerant to succinylcholine. Other useful medications include alfentanil and meperidine, particularly when pain is the trigger, and doxapram (1.5 mg/kg) for increasing respiratory depth. Nitroglycerin (4 mcg/kg) is effective but only acts on smooth muscle, not skeletal muscle of the vocal cords.

Gentle thoracic pressure at 20-25 compressions per minute can reverse the spasm, possibly by forcing air through a partially open airway or by stimulating the Hering-Breuer deflation reflex. Larson’s Maneuver (with limited scientific evidence regarding its therapeutic use), involving bilateral pressure on the mastoid processes, can also stop laryngospasm by causing pain and relaxing the vocal cords. As a last resort, tracheal intubation, even if traumatic, or cricothyroidotomy/tracheostomy may be necessary in extreme emergencies.

REFERENCES

1) Flick RP, Wilder RT, Pieper SF, et al. Risk factors for laryngospasm in children during general anesthesia. Pediatr Anesth 2008; 18:289–296. In this report, the authors have identified the risk factors for laryngospasm in a case–control study and have concluded that URI, airway anomaly and the use of LMA increases the risk of laryngospasm.

2) Cortez E. Update on the management of laryngospasm. Journal of Anesthesia & Critical Care. 2018; 8(2): 1-6

3) Von Ungern-Sternberg BS, Boda K, Chambers NA, Rebmann C, Sly pD, Sly PD, et al. Risk assessment for respiratory complication in paediatric anesthesia: A prospectie cohort study. Lancet. 2010; 376: 773-83.

4) Burgoyne LI, Anghelescu DL. Interventon steps for treating laryngospasm in pediatric patients. Paediatr Anaesth. 2008; 18(4): 297-302.

5) Molyneux M. Managing Emergencies in Paediatric Anaesthesia (MEPA): a national collaborative paediatric simulation project. Bulletin of the Royal College of Anaesthetists 2007; 43: 2197–2199.

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