Anesthesia for ENT surgery is one of the most challenging because of the frequency of airway obstruction in infants and small children and requisite sharing of the airway that is often at a distance from the anesthesiologist. The trainee must learn a variety of airway management techniques that are appropriate for each type of procedure and the different types of airway instruments used by otolaryngologists.
Ear Surgery
Myringotomy and Tube Placement
Otitis media is a viral or bacterial infection that develops within a transudate in the middle ear space. The fluid accumulation results from eustachian tube dysfunction or adenoid hypertrophy and inflammation. These children present with fever and upper respiratory tract infections that do not abate until the ear fluid is drained. Myringotomy and tube placement consist of the insertion of tiny ventilating tubes through the tympanic membrane to drain fluid from the middle ear and prevent future fluid collections ( Fig. 22.1 ). It is the most common surgical procedure requiring general anesthesia in children.
The major focus of the preoperative assessment is to ensure that the child does not have any lower airway symptoms that indicate acute reactive airway disease or pneumonia, and that the child is no worse than their usual baseline state of health.
The standard anesthesia technique for myringotomy and tube placement consists of an inhaled induction with sevoflurane, with or without nitrous oxide (N 2 O). Premedication with a short-acting anxiolytic (e.g., oral midazolam) is institution-dependent. Once the child has reached a depth of general anesthesia sufficient to prevent response to a painful stimulus, the anesthesia provider turns the child’s head to the side while maintaining mask anesthesia, and the tubes are placed by the surgeon using a microscope ( Fig. 22.2 ). Intravenous (IV) access is not necessary unless the child has a comorbidity that necessitates administration of IV fluids or medications. Each ear tube insertion typically lasts no more than 5 minutes. Many children will manifest upper-airway obstruction when the head is turned. This usually resolves with application of continuous positive airway pressure (CPAP) or placement of an oral airway ( Fig. 22.3 ). Laryngospasm may occur if the depth of anesthesia is insufficient. Central or obstructive apnea may occur and is treated with positive-pressure ventilation. An oral airway may also be helpful postoperatively to prevent upper-airway obstruction in the recovery phase.
Significant postoperative pain may occur in some children immediately after the procedure and can occasionally last a few hours. Thus, prophylactic analgesia is indicated. Choices include acetaminophen, ibuprofen, or (rarely) oxycodone. Intranasal or intramuscular fentanyl 1 to 2 μg/kg, administered while the child is anesthetized, provides adequate postoperative analgesia and decreases agitation during emergence from general anesthesia without prolonging discharge times. Some anesthesiologists administer intranasal or intramuscular ketorolac intraoperatively. In a large retrospective study, combination intramuscular fentanyl and ketorolac was strongly associated with superior postanesthesia care unit (PACU) analgesia, reduced oxycodone rescue, and absence of clinically significant increases in recovery time or emesis incidence, compared with either medication alone. Healthy children may be safely discharged within an hour of completing the procedure.
Tympanomastoidectomy
Indications for a tympanomastoidectomy include chronic otitis media or the presence of a cholesteatoma. A cholesteatoma is a benign cyst made of squamous epithelia. It may present as a continuum of chronic otitis media and can cause damage to the middle ear ossicles leading to hearing loss. Cholesteatomas may be congenital (primary) or acquired (secondary). Secondary causes include tympanic membrane perforation or prior surgery.
A traditional tympanomastoidectomy is performed through an incision behind the ear to expose the mastoid, ear canal, and tympanic membrane or through the ear canal with endoscopic assistance. The ear canal is occasionally widened, and a portion of the mastoid bone is removed to allow access to the area of pathology. The eardrum is reconstructed, and the cholesteatoma is removed. The procedure is performed in the supine position with the child’s head turned away from the side of the surgery. The operating room (OR) table is turned 90 to 180 degrees away from the anesthesia machine ( Fig. 22.4 ). Therefore, you will need to anticipate the requirement of a breathing circuit with sufficient length. During the procedure, the head and neck are completely covered with drapes that will impede access to the airway. There is minimal blood loss or third-space fluid losses. The surgeon may use facial nerve monitoring, which precludes the use of a neuromuscular blocker. A temporary urinary catheter should be considered for procedures greater than 4 hours duration. Hyperthermia is possible if a warming blanket is used. The main postoperative concern is nausea and vomiting, so multimodal antiemetic prophylaxis should be administered. Postoperatively, children may be discharged home if they are well hydrated and do not have severe pain. The infiltration of local anesthesia at the incision site, and administration of oral or rectal acetaminophen will aid in postoperative analgesia. The extubation plan should be discussed with the surgeon, who may prefer a deep extubation technique to eliminate coughing, which has been known to cause graft displacement.
Tympanoplasty
A tympanoplasty is a repair of a perforated eardrum, usually with a temporalis fascia graft. It may also involve reconstruction of the bones of the middle ear. A postauricular approach is most often used; however, many otolaryngologists have been now performing this procedure with endoscopic assistance in a transcanal approach. All anesthetic implications and techniques are the same as those for tympanomastoidectomy.
Nasal Surgery
Nasal Cautery
Nasal cautery is performed in children who have chronic epistaxis secondary to friable blood vessels along the anterior portion of the nasal septum. The procedure consists of brief electrocauterization and typically lasts no more than 10 to 15 minutes. Some anesthesiologists may choose to provide mask anesthesia while intermittently removing the mask for the surgeon to cauterize the vessels. Supraglottic mask anesthesia or endotracheal tube placement are reasonable options, especially if the child is expected to bleed into the back of the pharynx. Postoperative analgesia is minimal and usually treated with acetaminophen or ibuprofen.
Nasal Fracture Reduction
Displaced nasal fractures are common in children, usually from falls or sports injuries. The fracture should be reduced within 14 days of the injury, after the initial period of swelling but before healing begins. Closed reduction consists of the manipulation of the nasal bones externally with the assistance of instruments through the nasal openings. Bleeding is typical, though not enough to be clinically important. However, there is a significant amount of blood that enters the nasopharynx. For this reason, most pediatric anesthesiologists will choose laryngeal mask airway (LMA) placement or endotracheal intubation for airway management and will thoroughly suction the pharynx before removal. The surgeon may choose to place a throat pack to minimize the chance of aspirating blood. Postoperative pain in the recovery room may require opioid analgesia, however home-based opioid use is not typically needed. Because postoperative nausea and vomiting are common, a prophylactic multimodal antiemetic approach is indicated.
Juvenile Nasopharyngeal Angiofibroma Resection
A juvenile nasopharyngeal angiofibroma (JNA) is a benign vascular tumor of the posterior nasopharynx that can spread into contiguous structures. Adolescent boys are most often affected and present with chronic nasal obstruction or painless, typically unilateral nasal bleeding that is not associated with trauma. The management of JNA is difficult because the lesion receives abundant vascular blood supply. Most patients will undergo preoperative embolization to limit intraoperative bleeding, which may be severe. An endoscopic nasal approach is then used for complete resection. Preoperative assessment includes a complete blood count, coagulation studies, and a type-and-crossmatch. After induction of general anesthesia and tracheal intubation (usually with a Ring-Adair-Elwyn [RAE] tube), two large-bore IV catheters are inserted for volume replacement and possible blood transfusion. An arterial line is often placed, depending on the extent of the procedure. A temporary urinary catheter should be placed because the duration of the surgery is often many hours. At the end of the procedure the nasal cavity is frequently packed. Depending on the extent of the surgical resection these children may remain intubated at the end of the procedure and mechanically ventilated in the intensive care unit (ICU) until their vital signs and fluid status have stabilized.
Upper Airway Surgery
Laryngomalacia and Supraglottoplasty
Laryngomalacia is the most common cause of chronic extrathoracic airway obstruction in infants. The typical endoscopic findings are of a curled epiglottis and floppy arytenoids with foreshortened aryepiglottic folds that cause the arytenoids to prolapse toward the glottic opening during inspiration, resulting in inspiratory stridor. The symptoms worsen in the first several months of life. The stridor is usually more prominent when the infant is lying supine, crying, or feeding. In most cases, the stridor is loudest between 4 to 8 months of age and resolves during the first year of life. However, some cases may cause chronic hypoxemia and may interfere with normal feeding and subsequent growth. These cases may require surgical intervention, which includes rigid bronchoscopy to rule out synchronous airway lesions and a supraglottoplasty. The purpose of the supraglottoplasty is to trim portions of the supraglottis that obstruct the airway (this is variable in different infants). Most commonly, the aryepiglottic folds need to be lysed and the cuneiform cartilages of the arytenoids may also need to be trimmed. Various instruments may be used including cold steel, CO 2 laser, or shaver. During induction of general anesthesia, infants with laryngomalacia will demonstrate airway obstruction that is not relieved by placement of an oral airway device. Deepening the anesthetic will often relieve the obstruction because of progressive weakening of the diaphragm and decreasing the strength of inspiration. However, during upper-airway obstruction, speed of inhaled induction is slowed. Positive-pressure ventilation is usually easily accomplished in these infants, especially after the onset of neuromuscular blockade. Topical lidocaine is often used to mitigate the risk for laryngospasm during bronchoscopy and supraglottoplasty. When the CO 2 laser is used in the airway, standard laser safety precautions will apply.
Obstructive Sleep Apnea and Tonsillectomy
There are two common reasons why children have their tonsils removed: recurrent infection and obstructive sleep apnea (OSA, or “sleep disordered breathing”). OSA is the result of adenotonsillar hypertrophy, often combined with an abnormally small retropharyngeal space, and altered neuromuscular control of upper-airway patency during sleep. It mainly occurs in children between the ages of 2 and 6 years (although infants and older children may also have it), and is especially prevalent in children with obesity, trisomy 21, neuromuscular disease, and craniofacial abnormalities. The clinical manifestations include partial or complete upper-airway obstruction during sleep, restless sleep, enuresis, morning headaches, behavioral disturbances, and daytime somnolence. Severe cases of untreated long-standing OSA can result in chronic hypoxemia, polycythemia, cor pulmonale, growth delays, behavioral problems, and learning difficulties.
Diagnosis of OSA in children is mainly by clinical characteristics, but an overnight sleep study using polysomnography (PSG) may be performed to confirm the diagnosis and is recommended in children with comorbidities, such as obesity, trisomy 21, craniofacial abnormalities, neuromuscular disorders, sickle cell disease, or mucopolysaccharidoses. OSA is measured by the apnea-hypopnea index (AHI), which is the average number of apnea or hypopnea events per hour. OSA can be categorized as as mild, moderate, or severe ( Table 22.1 ). The most common therapy for pediatric OSA is adenotonsillectomy, which alleviates symptoms in most children.
| Type | Apnea-Hypopnea Index (Events Per Hour) | SpO 2 < 90% During Total Sleep Time |
|---|---|---|
| Mild | 1–5 | 2%–5% |
| Moderate | 5–10 | 5%–10% |
| Severe | >10 | >20% |
Preoperatively, some pediatric anesthesiologists reduce the dose of the preoperative sedative in children with OSA, for fear of causing life-threatening upper-airway obstruction if the child is waiting in an unmonitored environment. During induction of general anesthesia, virtually all children with untreated OSA will exhibit partial or complete upper-airway obstruction. Insertion of an oral airway device after loss of consciousness will bypass the obstruction and allow easy bag-mask ventilation. In the immediate postoperative period after adenotonsillectomy, the incidence of airway obstruction is higher in children with OSA compared with those who undergo adenotonsillectomy for recurrent infections. Therefore, children with significant OSA should be monitored closely after the procedure, and those chosen on a case-by-case basis should be kept as an inpatient overnight. Even some time after adenotonsillectomy has been performed, a predisposition toward upper-airway obstruction during sleep or sedation may persist throughout childhood. Children with OSA are more likely to develop adult-type OSA.
Tonsillectomies in otherwise healthy children are performed as outpatient surgery unless the child has OSA and meets one of the criteria for overnight admission ( Table 22.2 ).
| Age <3–4 years |
| Moderate to severe OSA |
| Coexisting disease (e.g.,): |
|
Unless there is a history of a bleeding disorder in the child or the family, tonsillectomy patients do not require preoperative lab studies.
The goals of anesthetic management for tonsillectomy are a motionless patient during the procedure, a rapid and smooth emergence, postoperative pain relief, and control of postoperative nausea and vomiting. After induction of anesthesia, a cuffed oral RAE endotracheal tube is inserted to accommodate the mouth-opening device used by the surgeon. The cuff should be inflated to prevent oxygen from entering the surgical field, where it may fuel a fire if electrocautery is being used. Even with cuffed tubes, our routine practice is to keep the inspired oxygen concentration below 30% (without N 2 O) to minimize the risk for airway fire. Some pediatric anesthesiologists use a flexible LMA for airway management during tonsillectomy. Some anesthesiologists administer a neuromuscular blocker. Tracheal intubation, however, can be accomplished using deep sevoflurane anesthesia with propofol supplementation. Maintenance of anesthesia usually consists of an inhaled agent, or continuous infusion of propofol, or both. Propofol maintenance is associated with less postoperative nausea and vomiting. IV acetaminophen is now available to contribute to the analgesic regimen, although some centers may place restrictions on its use because of the cost.
Once the endotracheal tube or LMA is appropriately secured, the table is turned 90 degrees. A booster roll may be placed underneath the shoulders of the patient, and the head is placed in extension. Care must be taken in patients with trisomy 21 because of the possibility of atlanto-axial subluxation (see Chapter 9 ). When the surgeon inserts the mouth gag, the child’s mouth is maximally opened. During this process the endotracheal tube may be pulled out of the trachea or critically compressed. Therefore, you should ensure that ventilatory parameters remain the same as before the gag was placed. In addition, because of the surgeon’s viewpoint from above the head of the child, he or she may not notice that certain portions of the lips and tongue have become pinched by the gag. You should carefully observe this process to ensure that injury does not occur.
Adjuvant medications include an opioid for pain and either a 5-HT 3 antagonist or dexamethasone (or both) to help prevent postoperative nausea and vomiting. Young children with recurrent hypoxemia because of OSA have reduced opioid requirements ; thus titration is essential to avoid respiratory depression. Dexamethasone decreases the incidence of postoperative nausea and vomiting, is associated with improved postoperative fluid intake, and lessens the severity of postoperative pain.
During tonsillectomy, there are several anesthetic concerns. Blood loss varies and may be significant but is difficult to measure. However, it is rarely severe enough to warrant transfusion. Fluids should consist of an isotonic solution to replace the preoperative deficit, blood loss, and minimal insensible losses. Hypotonic fluids should never be used intraoperatively or postoperatively as profound hyponatremia with seizures and cerebral edema may occur. Some surgeons prefer to infiltrate the tonsillar fossae with a local anesthetic to decrease postoperative pain. Others, however, feel that this practice results in a higher incidence of postoperative bleeding and has been associated with brainstem trauma. For this reason, this is no longer an accepted practice during tonsillectomies. At the end of the procedure, the surgeon may pass a soft catheter to suction gastric contents. However, blood is rarely recovered, and there is no evidence that this practice influences the incidence of postoperative nausea and vomiting.
Once the surgeon has completed the procedure, the table is turned back and an oral airway or soft bite block is inserted into the mouth to prevent the child from biting down and compressing the endotracheal tube during emergence. The nasal passages are gently suctioned for secretions and excess blood. The catheter should go no farther than the anterior nasal cavity to avoid irritating the raw adenoid bed in the nasopharynx. Similarly, oral suctioning should be gentle and limited to the anterior midline of the oral cavity so that the tonsillar fossae are avoided. Bright, red blood that is continually suctioned during emergence should prompt an exploration of the area before the child awakens.
There are two schools of thought with regard to the safest and most appropriate method for emergence and tracheal extubation after tonsillectomy: wide-awake versus deeply anesthetized. The major advantage of a wide-awake extubation is the patient’s conscious ability to maintain airway patency immediately after the procedure. The main purported disadvantage is an increased tendency for bleeding secondary to coughing and gagging during emergence, which may lead to bleeding at the surgical site. The main advantage of a deep extubation is the avoidance of bleeding during emergence, and the facilitation of throughput in a busy surgical suite. Disadvantages include possible respiratory depression and failure to maintain airway patency, and laryngospasm during the semiconscious phase of emergence as a result of secretions or blood in the larynx.
After an awake tracheal extubation, the child is carefully observed for several minutes to ensure airway patency and the ability to maintain spontaneous ventilation without hypoxemia. The child should be kept in the operating room until he or she demonstrates the ability to maintain a patent airway without jaw thrust or chin lift. Occasionally, an oral airway may be left in place during transport to the postoperative care unit. The classic “tonsil position” with the child lying on one side and with the head lower than the body will facilitate upper-airway patency and draining of secretions from the mouth ( Fig. 22.5 ).
Patients at high risk for airway complications (i.e., OSA, craniofacial abnormalities) should be extubated wide-awake. Coughing during emergence can be minimized by administering a moderate dose of intraoperative morphine (0.05–0.1 mg/kg) and/or dexmedetomidine (0.5 mcg/kg). Using this awake extubation technique, bleeding during emergence and postoperative laryngospasm are infrequent.
Other centers, however, are equally adamant about the efficacy and safety of the deep extubation technique. This technique requires a relatively greater use of inhaled agent and less opioid, to facilitate adequate airway patency after tracheal extubation. If deep extubation is routinely used, the institution must develop a culture within the postoperative recovery site that facilitates expedient treatment of transient airway obstruction and laryngospasm.
An additional practice model in some institutions consists of the patient being moved to the PACU immediately after completion of the surgical procedure. The child is then allowed to fully emerge from general anesthesia under the watchful care of the PACU staff (which may or may not consist of additional anesthesia personnel). Tracheal extubation is performed when the child is fully awake.
The most important postoperative concern after tonsillectomy is upper-airway obstruction. The precise cause is unknown and may be related to airway edema, residual effects of general anesthesia or opioids, the child’s predisposition to upper-airway obstruction, or a combination of these. It occurs more often in children less than 3 years of age, and in children with preexisting sleep apnea. It most often manifests within the first 30 minutes postoperatively. Delayed upper-airway obstruction is uncommon, but when it occurs is usually related to opioid use. Initial treatment consists of optimal placement of the head and neck in a position that is most consistent with airway patency (lateral positioning may be helpful), cool mist in oxygen, and administration of corticosteroids if not already given. If these measures fail to relieve continuing hypoxemia (SpO 2 <90%), placement of a soft lubricated nasopharyngeal airway is indicated ( Fig. 22.6 ). Most children with distress secondary to upper-airway obstruction will allow placement of this device without much of a struggle. If a nasopharyngeal airway is necessary, the child should be admitted to a postoperative hospital unit with close nursing supervision (e.g., intensive care unit). To enhance oxygenation after placement of a nasopharyngeal airway, it can be connected to a ventilation device to administer CPAP ( Fig. 22.7 ). Should the child remain hypoxemic despite placement of a nasopharyngeal airway, tracheal intubation is then indicated, with a trial of extubation at a later time.
