General Considerations

General Considerations

1. Airway. The airway is often shared with the surgeon. Pathology, scarring from previous surgery or irradiation, congenital deformities, trauma, or manipulation can produce chronic or acute airway obstruction, bleeding, and a potentially difficult airway. Preoperative discussion with the surgeon and analysis of previous anesthetic records regarding perioperative airway management, endotracheal tube size and position, patient positioning, and use of nitrous oxide and muscle relaxants are essential. The patient may require awake examination of the airway under sedation and topical anesthesia or an awake fiberoptic intubation before induction of general anesthesia.
2. Patients presenting for ORL surgery may have a history of heavy smoking, alcohol abuse, obstructive sleep apnea (OSA), and chronic upper respiratory tract infections. Preoperative testing should be dictated by medical comorbidities.
3. In addition to standard monitors, intra-arterial blood pressure and urine output monitoring may be needed for lengthy cases or surgeries with significant anticipated blood loss.
4. Extubation after any upper airway surgery requires careful planning. Extubation is performed once the throat packs are removed, the pharynx is suctioned, and full protective laryngeal reflexes return. Excessive upper airway bleeding, edema, or pathology may preclude extubation in the operating room.

Ear Surgery

Ear Surgery

1. Preoperative considerations
   1. Ear surgery often involves dissecting and preserving the facial nerve (CN VII). Primary anesthetic concerns include patient positioning, facial nerve preservation, use of nitrous oxide, adequate hemostasis, smooth emergence, and prevention of PONV.
   2. The middle ear communicates with the oropharynx via the eustachian tube. If eustachian tube patency is compromised by trauma, edema, inflammation, or congenital deformity, normal venting of middle ear pressure cannot occur. In this situation, a high concentration of nitrous oxide can increase middle ear pressure to 300 to 400 mm Hg in 30 minutes. Conversely, acute cessation of nitrous oxide can result in rapid resorption and a net negative pressure in the middle ear. These changes may result in alteration of middle ear anatomy, rupture of tympanic membrane, disarticulation of artificial stapes, disruption of surgical grafts, and PONV.
   3. Positioning. During surgery, the patient's head often is elevated and turned to the side. Extremes of head position should be assessed preoperatively to determine limits of range of motion, especially in patients with arthritis or cerebrovascular disease. Furthermore, attention to adequate venous drainage is necessary with extremes of head position.
2. Anesthetic technique. Anesthesia is induced with a hypnotic and short-acting muscle relaxant or by inhalation and is maintained with a volatile anesthetic or total intravenous anesthesia (TIVA). The use of nitrous oxide should be discussed with the surgeon or avoided; nitrous oxide should be discontinued at least 30 minutes before placement of a tympanic membrane graft.
   1. Delicate microsurgery of the ear requires adequate hemostasis. Volatile anesthetics, remifentanil, and α- or β-adrenergic antagonists work well to maintain mean arterial pressures of 60 to 70 mm Hg. Elevation of the head of the bed to approximately 15 degrees to decrease venous congestion and local application of epinephrine for vasoconstriction usually improve operating conditions.
   2. Myringotomy with tube placement is one of the most frequently performed outpatient pediatric surgeries. These procedures are short and can usually be performed under mask anesthesia with or without an IV placement. Deep anesthesia using volatile anesthetics alone or in combination with remifentanil can be used. If the procedure is performed without an IV line, intranasal fentanyl (1 to 2 μg/kg) and preoperative oral acetaminophen (20 to 40 mg/kg) can be used for postoperative pain management.

Nasal Surgery

Nasal Surgery

1. Anesthetic technique. Nasal surgery can be performed with local or general anesthesia. With either technique, the surgeon may initially apply 4% cocaine to the nasal mucosa, followed by injection of 1% to 2% lidocaine with 1:100,000 to 1:200,000 epinephrine for hemostasis. These agents may cause tachycardia, hypertension, and arrhythmias. In a healthy adult, the cocaine dose should not exceed 1.5 mg/kg (each drop of a 4% solution contains about 3 mg of cocaine). Smaller doses should be used when administered with epinephrine or in patients with cardiovascular disease. General anesthesia may be needed to provide immobility, airway protection, or amnesia.
   1. For endoscopic sinus surgery, some providers advocate for total intravenous anesthesia (TIVA), which has been associated with decreased blood loss as compared with volatile anesthetics.
2. After nasal cosmetic surgery, the nose is unstable and application of a face mask is undesirable. Smooth emergence and extubation are important to decrease postoperative bleeding and to avoid laryngospasm and the need for positive-pressure ventilation by mask.
3. Blood loss during nasal surgery may be substantial and difficult to estimate. A throat pack may help decrease PONV by preventing passage of blood into the stomach. An orogastric tube may be placed to evacuate the stomach of any swallowed blood.
4. Patients with severe epistaxis presenting for internal maxillary artery ligation or embolization often are anxious, hypertensive, tachycardic, and hypovolemic. They are assumed to have a full stomach containing blood and induction of anesthesia, and endotracheal intubation should be planned accordingly. Hypertension should be controlled to reduce blood loss. Posterior nasal packing, while helpful, can cause edema and hypoventilation. Because the extent of blood loss is difficult to assess, adequate IV access (16- or 18-gauge IV) and blood for transfusion should be available. Removal of the posterior packing can be associated with substantial blood loss.

Upper Airway Surgery

Upper Airway Surgery

1. Tonsillectomy and adenoidectomy
   1. Preoperative evaluation should seek a history of bleeding disorders, recent respiratory tract infection, and OSA. The STOPBANG questionnaire for OSA is a useful screening tool.
      1. Do you snore loudly at night?
      2. Do you feel tired during the day?
      3. Has anyone observed apnea?
      4. Do you have or are you being treated for high blood pressure?
      5. Is your BMI greater than 35?
      6. Is your age over 50?
      7. Is your neck circumference over 17 inches (male) or 16 inches (female)?
      8. Is your gender male?A score of 5 or greater is strongly predictive of OSA. Patients with OSA may be difficult to ventilate and intubate. These patients also have an increased incidence of postoperative respiratory complications and should be considered for prolonged observation in the PACU or overnight admission to monitor for respiratory compromise.
   2. Most children receive an inhalation induction, followed by placement of an appropriately sized IV. A technique consisting of a volatile agent, supplemented with an opioid (e.g., morphine 0.05–0.1 mg/kg IV), usually is performed. Muscle relaxation facilitates intubation but is not mandatory. Inadvertent endotracheal tube obstruction, disconnection, or dislodgement can occur during head and mouth gag manipulation. Endotracheal tubes should be firmly secured at the midline of the mandible for surgical access.
   3. At the end of surgery, the throat pack should be removed, an orogastric tube should be placed to empty the stomach of any swallowed blood, and the pharynx should be suctioned thoroughly. Administration of antiemetic agents should be considered. Extubation may be performed under deep anesthesia or when the patient is awake with intact airway reflexes. The use of an oropharyngeal airway after surgery can cause surgical wound disruption and bleeding if not carefully placed in the midline. Nasal airways are useful alternatives.
   4. Auscultate for unobstructed breathing before transport to the postanesthesia care unit (PACU) and checked for a dry pharynx before discharge.
2. Tonsillar rebleeding
   1. Rebleeding after a pediatric tonsillectomy occurs in approximately 5% of cases. Primary bleeds occur within 24 hours after surgery. Secondary bleeding is common 7 to 10 days postoperatively as the eschar sloughs. Hematemesis, tachycardia, frequent swallowing, pallor, and airway obstruction may be seen. The extent of blood loss is often underestimated because the blood is swallowed.
   2. Posttonsillectomy hemorrhage is a surgical emergency, and induction of anesthesia in a bleeding, hypovolemic child can result in severe hypotension or cardiac arrest. Appropriate IV access is necessary, and the patient should be adequately resuscitated (with blood products if necessary) before reoperation. Hematocrit, coagulation studies, and availability of blood products should be ascertained. Doses of anesthetic agents may need to be reduced in the setting of hypovolemia.
   3. Because the stomach is full of blood, a rapid-sequence induction should be performed. Two working suctions and an additional styletted endotracheal tube one size smaller than anticipated should be available. The surgeon should be present. Extubation is safest with the patient awake.
3. A tonsillar or parapharyngeal abscess may present with trismus, dysphagia, and a distorted, compromised airway. The surgeon may be able to decompress the abscess with needle aspiration before the induction of anesthesia. If needed, an awake fiberoptic intubation may be performed. Anesthetic management and extubation procedures are similar to those for tonsillectomy. In Ludwig angina, a cellulitis of the submandibular and sublingual spaces may extend to the anterior compartments of the neck. Trismus, airway edema, and distorted anatomy often make visualization by direct laryngoscopy of the glottic opening difficult. General anesthesia is contraindicated if stridor occurs at rest. Awake fiberoptic intubation is the safest approach in this scenario. If awake fiberoptic intubation is not possible, consider tracheostomy under local anesthesia to secure the airway.
4. Direct laryngoscopy is indicated for diagnostic (biopsy) or therapeutic (vocal cord polyp removal) purposes and may involve potentially compromised airways. Evaluation of imaging studies (magnetic resonance imaging or computed tomography) and laboratory studies (pulmonary flow-volume loops) may help identify airway abnormalities and potential perioperative problems. Many patients have a history of smoking and cardiopulmonary disease.
   1. Anesthetic management is described in Chapter 21, section IV.
   2. Postoperative airway edema may develop. If anticipated, dexamethasone (4 to 10 mg IV) may be given. Additional treatment includes head elevation, humidified oxygen by mask, and nebulized racemic epinephrine. Occasionally, cessation of nebulized racemic epinephrine is associated with the return of airway edema.
5. Laser use in ORL surgery. Laser (light amplification by stimulated emission of radiation) produces a high-energy, high-density beam of coherent light that generates focused heat on contact with tissue. The emission media used to produce the monochromatic light determines the wavelength.
   1. Short-wavelength (1 μm) laser (argon gas, ruby, neodymium: yttrium aluminum garnet [Nd:YAG]) emissions in the red-green visible part of the electromagnetic spectrum are poorly absorbed by water but well absorbed by pigmented tissues such as the retina and blood vessels.
   2. Infrared (10 μm) carbon dioxide laser emissions are well absorbed by water and superficial surface cells and are commonly used to treat laryngeal lesions. They cannot be transmitted through fiberoptics.
   3. Eyes must be protected from the laser beam. Operating room personnel must wear appropriate safety goggles (green tinted for argon, amber for Nd:YAG, and clear for carbon dioxide). The patient's eyes should be taped closed and covered with safety goggles.
   4. The most serious complication of laser airway surgery is airway fire. The likelihood of fire depends on the gas environment of the airway, the energy level of the laser, the manner in which the laser is used, the presence of moisture, and the type of endotracheal tube used. Oxygen and nitrous oxide both support combustion. A safe gas mixture during laser upper airway surgery is oxygen/air or oxygen/helium to achieve a fraction of inspired oxygen of 25% to 30%.
   5. Safe laser use. Lasers should be used intermittently, in the noncontinuous mode, and at moderate power (10 to 15 W). Surgeons should not use the laser as a cautery and should share responsibility for fire prevention by limiting the energy input, allowing time for heat dispersal, packing aside nontarget tissue and endotracheal tube cuffs with moist gauze, and maintaining moisture (as a heat sink) in the field.
   6. Airway options during laser surgery. Specially designed, fire-resistant, impregnated or shielded endotracheal tubes (e.g., Xomed Laser-Shield II endotracheal tube) are used, and the cuff is filled with blue saline. For some procedures, intubation is not possible because the surgeon requires free access to the surgical field. Options include the following:
      1. Jet-Venturi technique. This technique eliminates the need for an endotracheal tube, but airway fire may still occur due to dry tissue igniting. All patients are at risk for barotrauma; pediatric patients, patients with emphysema, and patients with chronic obstructive pulmonary disease are at highest risk.
      2. Ventilation and apneic oxygenation. The surgeon operates during periods of apnea and stops intermittently to allow the anesthesiologist to ventilate and oxygenate the patient.
   7. If an airway fire occurs, stop ventilation and immediately disconnect the endotracheal tube from the breathing circuit, remove the tube, pour saline in the pharynx to absorb the heat, suction, mask ventilate, and reintubate with a new endotracheal tube. After the fire is extinguished, examine the airway by bronchoscopy. Complications include airway edema, inhalation injury, tracheal and laryngeal granulation tissue formation, and airway stenosis.
   8. The anesthetic technique for laser surgery is similar to that described above (section II.D.5.f) and Chapter 21, section IV.E. Goals include adequate surgical exposure, fire prevention, and return of protective airway reflexes before extubation. Surgeons may or may not request muscle relaxants for vocal cord examination or manipulation; therefore, communication with the surgical team is essential before proceeding with induction. Endotracheal intubation, jet ventilation, or intermittent mask ventilation may be used. Regardless of the technique, a mixture of oxygen/air is essential (<30% oxygen). Because airway edema may occur, the patient is given humidified oxygen postoperatively and is observed closely in the PACU. Corticosteroids or aerosolized racemic epinephrine may be necessary.

Outline

• Anesthesia for Ophthalmic Surgery
• Anesthesia for Otorhinolaryngologic Procedures
• Anesthesia for Procedures of the Neck
• Suggested Readings