16. Anesthesia for Ear, Nose and Throat Surgery in Children
KeywordsAnesthesia for tonsillectomyAnesthesia for neck abscesses in childrenPediatric OSADexamethasone in tonsillectomy
Ear, nose and throat (ENT) surgery is the most common reason for anesthesia in children—1.5% of all children in Western Australia have an anesthetic for an ENT procedure each year. It involves the challenges of managing a shared and potentially soiled airway as well as the possibility of airway obstruction in the postoperative period. Safe anesthesia requires vigilance, good communication with the surgical team and flexibility of anesthetic technique. This chapter outlines the principles of anesthesia for common ENT procedures in children. Bronchoscopy of the airway is discussed in the next chapter.
16.1 Anesthesia for Ear Surgery
16.1.1 Myringotomy and Tubes (M&T)
Abnormal function of the eustachian tubes is common in children and may lead to otitis media with effusion (OME), or ‘glue-ear’. Small ventilation tubes, or grommets, are placed through the tympanic membrane to ventilate the middle ear and prevent hearing loss and speech delay. It is uncomplicated surgery lasting 10–15 min, with anesthesia using a LMA or facemask. Nitrous oxide is safe to use. The ears may be sore for a short time after surgery, and analgesia is required or the child may wake up distressed. Paracetamol with or without a small dose of opioid is usually sufficient for analgesia. Some anesthetists do not obtain intravenous (IV) access during anesthesia for M&T insertion. Proponents argue this saves time and avoids ‘handing over’ the airway while the IV is inserted. Analgesia is either omitted, given orally preoperatively, or with intranasal fentanyl intraoperatively. The obvious risk of this approach is the inability to administer IV drugs in an emergency, and prevention of emergence delirium is limited to fentanyl. It seems difficult to justify this risk when IV insertion only takes a matter of seconds in skilled hands.
16.1.2 Myringoplasty and Tympanoplasty
Myringoplasty is the repair of a chronic perforation of the tympanic membrane. Tympanoplasty is a more extensive repair that may include surgery to the middle ear bones. The surgical approach for both procedures is either transcanal or via an incision behind the ear. Anesthetic considerations include minimizing bleeding that may obscure the operative field and prevention of nausea and vomiting. Nitrous oxide may lift the graft off the tympanic membrane and should be discussed with the surgeon.
16.1.3 Cochlear Implant
Cochlear implant surgery can be life changing for children with severe sensorineural deafness by restoring hearing, speech development and communication. Electrodes run from a receiver under the soft tissue behind the ear through the mastoid and into the cochlea. These patients may have an underlying syndrome associated with their sensorineural deafness (such as Treacher Collins syndrome and Klippel-Feil anomaly), which may be associated with airway difficulties. Facial nerve monitoring is used during surgery, and the child is either intubated without a muscle relaxant or using a short-acting relaxant. TIVA is commonly used to help maintain tight blood pressure control and to reduce bleeding, and nausea and vomiting (PONV). Small doses of opioid and local infiltration by the surgeon achieve analgesia.
16.2 Tonsillectomy and Adenoidectomy
Tonsillectomy is a common procedure usually performed for obstructive sleep apnea (OSA) in preschool-aged children, and for recurrent tonsillitis in older children. Three percent of all children undergo tonsillectomy, and 80% of tonsillectomies are performed for OSA. Pre-operatively, children require assessment of co-existing conditions that affect upper airway size, such as Trisomy 21 or craniofacial abnormalities, and for bleeding disorders such as Von Willebrands disease. Most tonsillectomies are extracapsular, and the tonsil is removed by dissecting between the capsule and muscular wall. For intracapsular tonsillectomy, the capsule is left intact making the procedure less painful, but the tonsil may regrow later.
16.2.1 Obstructive Sleep Apnea
OSA is characterized by severely reduced or obstructed airflow during sleep caused by abnormal upper airway anatomy. The symptoms of OSA in children are different to adults. OSA is discussed further in Chap. 11, Sect. 11.8. In summary however, there are three broad causes of OSA in children. The first is soft tissue occupying the limited space in the upper airway, most commonly adenotonsillar hypertrophy, but also a large tongue in Trisomy 21. Secondly it is caused by hypotonia or discoordination of the pharyngeal muscles, and finally by bony abnormalities in craniofacial syndromes. The cause is frequently a combination of these three factors, for example a child with Robin sequence has a reduced airway size from micrognathia, but also has tonsillar hypertrophy of a degree that might not be a problem in a normal-sized airway.
OSA is common in preschool-aged children because their tonsils and adenoids are large relative to the size of their airway. Adenotonsillectomy is the initial treatment for OSA in children, and improves sleep study parameters, behavior and quality of life in both obese and non-obese children. Non-surgical treatment for OSA includes noninvasive ventilation during sleep, and nasal steroid sprays to reduce inflammation of the adenoids. The ENT surgeon usually diagnoses OSA clinically, and not all children require a sleep study to confirm the diagnosis before tonsillectomy. There is no consensus however, on which sub-group of children need a pre-operative sleep study. Typical criteria include suspicion of severe OSA, presence of a craniofacial syndrome, morbid obesity, neuromuscular disorders and young age. In addition, children who are a high anesthetic risk (such as those with cardiac or pulmonary disease) should have a pre-operative sleep study, as a normal result might avoid surgery.
Very rarely, children with severe OSA and co-morbidities (such as morbid obesity or a craniofacial syndrome) may have chronic hypoxia and hypercarbia with a reduced ventilatory response to both. This is rare in modern practice, and screening with ECG or CXR is not warranted unless there are clinical signs of cardiac dysfunction or unusually long-standing and untreated severe OSA. These children may be polycythemic with pulmonary hypertension and right ventricular hypertrophy. The presence of polycythemia and a right ventricular strain pattern on ECG (increased P wave lead 2 and large R wave V1) would suggest a sleep study and echocardiogram should be performed. In very severely affected children with pulmonary hypertension secondary to OSA, a brief period of non-invasive ventilation (BIPAP) may optimize them preoperatively.
OSA significantly increases anesthetic risk for tonsillectomy, particularly in children younger than 3 years.
Factors that increase the risk of airway obstruction after tonsillectomy in children with OSA
Risk factors for postoperative problems in children with OSA
Young age, especially less than 3 years
Craniofacial abnormality with reduced oropharyngeal size (e.g. Trisomy 21)
Severe OSA on polysomnography (10 or more obstruction/h, or SaO2 below 80%; RDI > 20)
Co-morbidities such as cardiac disease
16.2.2 Anesthesia Technique
There are many different techniques for anesthesia for tonsillectomy
IV or inhalational induction
Flexible LMA, oral RAE ETT in young children
More secure airway than LMA in young children
Pressure support ventilation or IPPV
Control CO2, maintain lung volume & reduce atelectasis
Paracetamol 15 mg preop or IV intraop
Fentanyl 1–2 μg/kg plus morphine 0.05 mg/kg IV
Comfortable once awake, but not obstructed
Parecoxib 0.6–0.9 mg/kg (max 40 mg)
Dexamethasone 0.15 mg/kg (max 8 mg)
Antiemetic, improves analgesia
Ondansetron 0.15 mg/kg (max 4 mg)
Hartmanns 10–20 mL/kg, continue maintenance rate postoperatively
Maintain hydration despite reduced oral intake postop
Safe airway for recovery
Opioid boluses once awake in recovery if required
Use small dose opioid intraoperatively, titrate further doses once child awake
Paracetamol 15 mg/kg, 6 hourly postop oral or IV
Oxycodone 0.05–0.1 mg/kg, 6 hourly prn
Analgesia required after discharge. Conservative paracetamol dose as likely to require for 7 days or more
Monitor oxygen saturation, observe for upper airway obstruction, excessive sedation, respiratory depression
Risk of OSA persists or may even be higher immediately postop
184.108.40.206 Airway Management
In many centers, endotracheal intubation is the routine airway of choice, but elsewhere the LMA is routinely used with endotracheal intubation reserved for small children and others at higher risk of airway obstruction during surgery.
A south-facing oral RAE tube is used for intubation in tonsillectomy. In small children, intubation can be achieved without the use of muscle relaxants (using a bolus of propofol after inhalational induction instead), although in larger children a small dose of relaxant (such as 0.25 mg/kg of atracurium) may be required to optimize intubating conditions. The ETT sits in the midline between the blade of the mouth gag and the tongue and gives a secure airway unlikely to be displaced and does not impede the operative field. Throat packs are not used as they obscure the surgical view, although the surgeon may place a gauze swab above the vocal cords to limit air leak if an uncuffed ETT is used. One must consider if the advantages of intubation (better surgical access in a shared airway, more definitive airway securement) outweigh some of the disadvantages (risks of intubation, time taken for airway instrumentation for an often high-turnover list). Occasionally a malpositioned or incorrectly sized surgical gag can obstruct the ETT after insertion, and it is best to test ventilate following the gag insertion and before commencing surgery.