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Laryngospasm is a life threatening complication of anesthesia. Incidence of laryngospasm is possible for all age groups but occurs more frequently in pediatric populations.1 Multiple preoperative risk factors have been identified which increase this risk. With prior knowledge, the anesthesia provider can implement proper airway precautions and anticipate spasm.
The larynx is responsible for phonation, the passage of air into and out of the lungs, and protection of the airway from esophageal contents. It is located in the anterior part of the neck, between the pharynx and the trachea. In contrast to the adult larynx, the pediatric larynx is located more anterior and higher in the neck, between the second and third cervical vertebra. In addition, the larynx is funnel shaped, the airway is smaller, the epiglottis is omega shaped and angled over the laryngeal inlet, the vocal cords are more angled, and the cricoid cartilage is narrower.
Laryngospasm is caused by rapid and sustained glottic closure due to stimulation of the superior laryngeal nerve and can be classified as partial obstruction or full obstruction.2 Partial laryngospasm involves the adduction of the true vocal cords which provides restrictive passage of air. Full laryngospasm involves the constriction of the false vocal cords and supraglottic soft tissue and is characterized by no air movement.
Laryngospasm can occur at any time during the administration of anesthesia and is considered a life threatening emergency. Obstruction of the airway in pediatric patients is of particular importance due to greater oxygen consumption in these patients.3 Hypoxic injury, negative pressure pulmonary edema, and death can occur.
Laryngospasm is more likely to occur during planes of lighter anesthesia. Direct stimulation by the anesthesia provider, such as suctioning, placement of an endotracheal tube or laryngeal mask (LMA) can provoke spasm. Inhalation agents can irritate the airways; saliva, blood, or gastric secretions can irritate the glottis.5 Painful stimuli in any part of the body as well as pelvic or abdominal stimulation can induce spasm.
Partial obstruction will manifest as audible stridor and the anesthesia provider may experience difficulty passing adequate volumes of air. Total obstruction presents as a complete lack of ventilation. The chest may continue to rise and fall with inspiratory effort but no air is exchanged. This paradoxical breathing is typically accompanied by retractions in the neck an upper thorax.
Treatment must be initiated immediately.2 Positive pressure with 100% oxygen should be applied as well as lifting the chin and bringing the mandible forward. Larsonâ€™s maneuver; pressure behind the earlobe, between the mastoid process and ramus of the mandible, should be attempted. Moreover, anesthesia should be deepened, either by increase of the inhalation agent or the use of intravenous propofol. If laryngospasm persists, a sub therapeutic dose of succinylcholine should be administered. Reintubation may be required to secure a patent airway.
Review of Current Literature
Laryngospasm most commonly occurs as the result of irritation of the airway. Multiple preoperative risk factors for laryngospasm have been identified. Current evidence suggests a correlation between upper respiratory infections (URI) and increased risk of airway obstruction.6 Children presenting with an active URI suffer from the highest risk; increased airway secretions exacerbate airway inflammation which can produce heightened sensitivity. This sensitivity decreases over 2 to 4 weeks but still poses a significant risk. Therefore, elective surgery should be postponed until 4 weeks have passed. If postponement of the surgical procedure is not possible, adjustment of anesthetic technique is necessary. Intravenous use of propofol for induction has been shown to be less irritating to the airways than the use of sevoflurane. An endotracheal tube was shown to have the highest risk and should be avoided if possible, however, the use of LMA is somewhat controversial.
Regardless of the status of URI, a retrospective study done of 130 children at the Mayo clinic found an increase in laryngospasm with the use of a LMA.7 This study also saw an increase in laryngospasm associated with concurrent URI, or recent URI of up to 4 weeks. There was no way to establish whether removal of an LMA was done during light or deep anesthesia or whether there were secretions associated with removal. As previously discussed, in order to decrease susceptibility to spams, proper maintenance of an adequate plane of anesthesia is necessary to decrease the effects of stimulation.
An observational study done of 335 children also concluded that incidence of laryngospasm in patients with an URI peaked in a 2 to 4 week period.4 Numerous symptoms were identified but multivariate analysis showed there was no association between specific symptoms and greater risk. An URI 4 to 6 weeks prior to surgery seemed to afford protection from laryngospasm. The sample size of children that exhibited this protection was weakly correlated so further research is required
In addition to URIs, passive exposure to smoke has been shown to increase the irritability of the airway and is a significant risk factor for laryngospasm.8 Greater risk is seen in patients with a primary care giver smoking or with 2 or more immediate family members smoking. In order to reduce respiratory problems, it is recommended that active smokers quit smoking 8 weeks prior to surgery. Nonetheless, there is no clear consensus as to what is an appropriate amount of time for cessation to passive exposure to smoke.
Obesity rates in children have increased dramatically over the last 30 years. As of 2006, 15.5% of children and adolescents are considered obese.9 While there is abundant research of adult populations and adverse respiratory events due to obesity, there is a dearth of similar studies in the pediatric population. Comorbidities associated with obesity such as gastroesophageal reflux disease (GERD) have been associated with increased risk of laryngospasm in adults but have not been adequately examined in children. A prospective study done in 2008 did not find a significant increase in laryngospasm in obese children. However, the authors suggest further research is warranted.
Laryngospasm is a life threatening emergency. A thorough preoperative assessment should be undertaken to identify the risk factors and tailor an anesthesia management plan with those risk factors in mind. Regardless of known risk, it is necessary for the anesthesia provider to always be vigilant and prepared for adverse events during the delivery of anesthesia.