CC
A 12-year-old female is scheduled for extraction of four bicuspids under intravenous (IV) general anesthesia. (Laryngospasm may occur more often in children because of the frequency of upper respiratory tract infections [URIs] in this patient population.)
HPI
Preoperative evaluation of the patient revealed no recent URIs. The lungs were clear to auscultation. After electrocardiography, blood pressure, pulse oximetry, and capnography monitors were applied, the patient was administered 4 L of oxygen and 2 L of nitrous oxide via nasal hood. Sedation was achieved using 4 mg of midazolam and 50 μg of fentanyl titrated to effect. Before administration of local anesthesia, 40 mg of propofol was infused. During the first extraction, respiratory stridor (a high-pitched, inspiratory “crowing” sound) was noted. A noisy, harsh sound was heard on inspiration through the precordial stethoscope, and the patient’s oxygen saturation decreased from 99% to 65%. Capnography indicated no ventilation. At this point, the respiratory noises ceased. Tracheal tug and paradoxical chest wall motion were observed (signs of upper airway obstruction), and the patient began to appear cyanotic.
PMHX/PDHX/medications/allergies/SH/FH
Noncontributory. A recent history of URI may indicate an increased risk of perioperative respiratory complications, especially laryngospasm. In the event of a recent URI, it may be prudent to reschedule surgery after a 2-week symptom-free period. Patients with reactive airway disease and those with exposure to passive smoke may be more prone to experience laryngospasm.
Examination
General. A harsh inspiratory noise, or crowing, is audible on inspiration, which is best heard through the precordial stethoscope. The patient’s skin color is assessed for signs of cyanosis, which is seen with severe hypoxemia. In pediatric patients, hypoxemia is often a late finding of decreased ventilation or apnea. End-tidal CO 2 (Et co 2 ) monitoring and use of the precordial stethoscope indicate hypoventilation or apnea before changes in pulse oximetry.
Oropharynx. The throat pack was removed, and there was no evidence of foreign bodies. Copious amounts of mucous secretions were observed. (Blood and mucus are common stimuli for airway irritation.)
Neck and chest. There was evidence of tracheal tug and paradoxical chest wall motion (despite chin-lift and jaw-thrust maneuvers). This phenomenon is the result of forced inspiration against a closed glottis.
Vital signs. The patient’s heart rate was 160 bpm, blood pressure was 145/78 mm Hg, Et co 2 was 0, and respirations were 0 breaths per minute.
Oxygen saturation. Oxygen saturation decreased from 99% to 65% with the onset of laryngospasm. (Continued decline in the oxygen saturation can result in respiratory acidosis.)
ECG. The patient was in sinus tachycardia. (This is a common finding, but hypoxia can trigger more life-threatening cardiac arrhythmias. Hypoxemia in children may result in bradycardia.)
Imaging
Imaging is not relevant in the acute management of laryngospasm. This is an anesthetic emergency and is diagnosed based on the clinical presentation. Chest films can be ordered if there is suspicion of foreign body aspiration or to aid in the diagnosis of negative-pressure or postobstructive pulmonary edema after the acute management of the airway.
Labs
None are indicated in the acute setting.
Assessment
Intraoperative laryngospasm during odontectomy under general anesthesia.
Treatment
Prompt recognition and treatment of laryngospasm usually results in a good outcome. Upon diagnosis, the airway should be suctioned clear of noxious stimuli, and the surgical site should be packed. Any foreign bodies should be removed from the oral cavity, and 100% oxygen is administered. Positive-pressure ventilation should be attempted, ideally with a two-person technique and jaw-thrust maneuver; this often “breaks” the laryngospasm. (Jaw thrust and pressure at the angle of the mandible may also assist in breaking laryngospasms.)
A technique described by Dr. N.P. Guadagni also has been found to be effective at “breaking” laryngospasm. This involves placing the middle finger of each hand anterior to the mastoid and posterior to the condyle. The fingers then press inward while at the same time positioning the mandible forward. If the patient cannot be ventilated, the plane of anesthesia may be deepened with a short-acting IV general anesthetic; this often obviates the need for a skeletal muscle relaxant.
In rare situations, these methods are unsuccessful, and it is necessary to administer succinylcholine, a short- and fast-acting depolarizing neuromuscular blocking agent. If IV access is not available, succinylcholine may be administered intramuscularly at a dose of 4 mg/kg. A dose of 20 mg intravenously is usually sufficient to break the spasm (pediatric dose, 0.25 mg/kg). However, up to 60 mg can be administered if laryngospasm persists. Rapacuronium, rocuronium, and mivacurium can be used for patients in whom succinylcholine is contraindicated. The longer half-life of these nondepolarizing muscle relaxants may require continuous bag-mask ventilation until spontaneous respiration resumes.
Bradycardia is common after administration of succinylcholine. This usually occurs in children and in adults after repeated doses. Atropine may be administered in an effort to prevent this. IV lidocaine 2 mg/kg administered before extubation was found to be effective in preventing postextubation laryngospasm in patients undergoing tonsillectomy. Other studies have found the prophylactic use of IV lidocaine to be ineffective.
Complications
Laryngospasm may produce partial or complete respiratory obstruction. Fortunately, early recognition and management allow for rapid resolution and minimal morbidity. However, with prolonged hypoxemia, the complications can be devastating. Laryngospasm may result in an acid–base disturbance, such as respiratory acidosis. Rare complications of laryngospasm include cardiac arrhythmias, anoxic brain injury, negative-pressure pulmonary edema, and death.
If succinylcholine is administered, the patient may complain of general postoperative myalgia secondary to the rapid muscle depolarization. Other potential complications of succinylcholine include masticator muscle rigidity, malignant hyperthermia, and hyperkalemic cardiac arrest (secondary to the transient hyperkalemia), which can be seen in patients with undiagnosed myopathies (e.g., Duchenne’s and Becker’s muscular dystrophies).
Discussion
Laryngospasm results in tight approximation of the true vocal cords ( Fig. 15.1 ). It is a protective reflex that is most commonly caused by a noxious stimulus to the airway during a light plane of anesthesia. The structural and functional bases of the laryngospasm reflex were described by Rex. Secretions, vomitus, blood, pungent volatile anesthetics, painful stimuli, and oral and nasal airways may elicit this protective reflex. Mediated by the vagus nerve, this reflex is designed to prevent foreign materials from entering the tracheobronchial tree. During laryngospasm, the false vocal cords and supraglottic tissues act as a ball valve and obstruct the laryngeal inlet during inspiration. Laryngospasm has a reported occurrence of 8.7 per 1000 patients receiving general anesthesia. It is 19 times more frequent than bronchospasm. Children with sleep-disordered breathing and a body mass index at or above the 85th percentile are more likely to experience laryngospasm.
