Anesthesia for Pediatric Surgery - Specific Pediatric Anesthesia Problems
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The Compromised Airway
The Compromised Airway
- Congenital abnormalities (e.g., choanal atresia, Pierre Robin syndrome, tracheal stenosis, or laryngeal web).
- Inflammation (e.g., tracheobronchitis or “croup,” epiglottitis, and pharyngeal abscess).
- Foreign bodies (FBs) in the trachea or esophagus.
- Neoplasms (e.g., congenital hemangioma, cystic hygroma, or thoracic lymphadenopathy).
- Initial management
- Administer 100% oxygen by face mask (continually assess oxygenation and ventilation).
- Keep the child as calm as possible. Evaluation should be efficient, because it may increase agitation and cause further airway compromise. Parents are invaluable in their ability to pacify their children and should remain with them as long as feasible.
- An anesthetist must be present during transport to the operating room. Oxygen, a resuscitation bag and mask, laryngoscope, atropine, succinylcholine, drugs suitable for sedation and hypnosis, appropriate endotracheal tubes and laryngeal mask airways, oral airways, and pulse oximetry must be available.
- Induction of anesthesia with a compromised airway
- Minimize manipulation of the patient. A precordial stethoscope and pulse oximeter are adequate monitors during the initial induction of anesthesia.
- The child may remain in a semisitting position, with the parents present if indicated. A gradual inhalation induction with sevoflurane is the next step. Airway obstruction and poor air exchange will prolong induction.
- Parents are asked to leave when the child becomes unconscious, and an IV is started. If indicated, atropine may be given at this time. Alternatively a preinduction IV may be started if there is concern for acute decompensation and proceed with IV or inhalational induction.
- Patients with croup may benefit from gentle application of continuous positive airway pressure, but any positive pressure can cause acute airway obstruction in patients with epiglottitis or an FB.
- The oral endotracheal tube should have a stylet and be at least one size smaller than the predicted size. If postoperative ventilation is anticipated (e.g., epiglottitis), a cuffed endotracheal tube may be indicated.
- At this point, patients usually are hypercarbic (ETCO2 between 50 and 60 mm Hg), but generally, this is well tolerated. Bradycardia is an indication of hypoxemia and requires immediate establishment of a patent airway.
- Perform laryngoscopy only when the child is deeply anesthetized. The decision to give a muscle relaxant depends on the situation. A muscle relaxant facilitates intubation and obviates the need for deep anesthesia in certain circumstances. In other cases, muscle relaxation may further compromise the airway. In general, orotracheal intubation should be accomplished before any further airway procedures are attempted. Bronchoscopy is indicated before intubation in cases of large upper airway FBs or friable subglottic tumors (e.g., hemangioma).
- A nasal tube may be more appropriate for illnesses that require several days of intubation (e.g., epiglottitis). An orotracheal tube may be changed to a nasotracheal tube at the end of the procedure, provided the oral intubation was easily accomplished. Never jeopardize a secure oral endotracheal tube for the sake of changing it to a nasal endotracheal tube.
- Children should be sedated during transport to the intensive care unit. A combination of a narcotic and a benzodiazepine, propofol infusion, or dexmedetomidine infusion or bolus can be effective. Breathing may be spontaneous or assisted during the immediate postoperative period. Propofol is not approved by the FDA for sedation of pediatric intensive care patients due to the risk of propofol infusion syndrome and its associated metabolic derangements.
- Management of the inhaled Foreign Body (FB)
- FB aspiration usually occurs between 7 months and 4 years of age. About 75% of FBs lodge in the proximal airway (larynx, trachea, and right/left mainstem bronchus). Most deaths occur at the time of aspiration, and the mortality in most series is zero if the child reaches the hospital alive.
- Choking and wheezing following a witnessed aspiration event is the most common presentation. The triad of coughing, wheezing, and reduced breath sounds is present in only 50% of cases. Chest x-ray may show radiopaque objects, postobstructive emphysema, or a localized pneumonia but has a false-negative rate of 40%.
- Management is prompt rigid bronchoscopy regardless of chest x-ray findings. It is vital to communicate with the bronchoscopist before and during the procedure. An emergency tracheotomy and thoracotomy kit should be prepared. There are two approaches to the anesthetic: spontaneous ventilation and controlled ventilation.
- Spontaneous ventilation: After preoxygenation and IV atropine or glycopyrrolate, a sevoflurane/100% oxygen induction is performed. Sevoflurane is preferred for inhalational induction, and spontaneous ventilation is maintained. Once an adequate depth is achieved, the vocal cords and subglottic space are sprayed with topical lidocaine (2% for school age children and 1% for small infants). The trachea is then intubated with a ventilating bronchoscope. A sufficient depth of anesthesia is required to prevent moving and coughing. Consider a small dose of muscle relaxant just before removal of the FB through the vocal cords. The stomach is then suctioned, and the patient is allowed to emerge breathing through either a mask or an endotracheal tube placed after FB removal. Advantages of this technique are better air flow distribution and ventilation–perfusion matching, uninterrupted ventilation, and the ability to immediately assess ventilatory mechanics after FB removal. Disadvantages are the risks of patient movement, coughing, laryngospasm, and prolonged emergence.
- Controlled ventilation: Anesthesia is commenced with a rapid sequence induction using propofol and a muscle relaxant. Maintenance anesthesia can be provided with propofol and remifentanil infusions and muscle relaxant. The trachea is intubated with a ventilating bronchoscope, and ventilation is performed in concert with the bronchoscopist's interventions. When the bronchoscope is in place, ventilation is achieved with high inspiratory pressures, and long expiratory times are necessary to prevent barotrauma. Emergence is achieved in a manner similar to the spontaneous ventilation technique. The advantages of controlled ventilation are rapid control of the airway, no patient movement, and lower anesthetic requirements. However, ventilation is intermittently interrupted, and there are risks of displacing the FB distally and causing barotrauma with ball-valve hyperinflation.
- A large retrospective study showed that ventilatory technique did not affect the success of FB removal or influence adverse outcomes (hypoxia, hypercarbia, bradycardia, and hypotension).
- Subglottic edema resulting in postextubation croup can be treated with humidified oxygen. If symptoms are severe, then racemic epinephrine (0.5 mL of a 2% solution in 2 to 4 mL of volume) can be given. In addition dexamethasone (0.25 to 0.5 mg/kg up to 8 mg) should be considered.