ANESTHESIA FOR OTOLARYNGOLOGY

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Surgical procedures involving the eyes, ears, nose, and

throat require a cooperative relationship between the

surgeon and the anesthesiologist. It is important for the

anesthesiologist to appreciate the anatomy and physiology

of the structures in the operative field.

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In addition, an understanding of the surgical procedure is important.

Patients undergoing surgical procedures on the , head,

and neck represent a diversity of age groups from infants

to the elderly.

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It is important to appreciate that manipulation of the larynx, pharynx, and neck may precipitate cardiac dysrhythmias and that blood loss can be underestimated as a result of hidden losses within the surgical drapes and blood swallowed into the stomach.

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Damage to nerves that innervate the pharynx, larynx, and

especially the vocal cords (may be manifested promptly

after tracheal extubation) can occur during head and neck

surgery. The presence of laryngeal and pharyngeal edema

should be considered before tracheal extubation.

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SPECIAL CONSIDERATIONS FOR HEAD AND NECK SURGERY

Most patients scheduled for head and neck surgery will

have their airway examined by the surgeon before surgery.

The anesthesiologist should communicate with the surgeon about the probability of a difficult airway and whether nasal or oral tracheal intubation is indicated for optimal surgical exposure.

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An awake fiberoptic intubation of the trachea or a tracheostomy under local anesthesia may be

indicated if difficult upper airway management is anticipated.

The anesthesiologist should be familiar with the variety

of endotracheal tubes that are available for head and neck

surgery to facilitate better surgical exposure

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LARYNGOSPASM

Instrumentation or manipulation of the endolarynx or

the presence of blood or a foreign body can induce laryngospasm.

Laryngospasm is an exaggerated and prolonged

response of the protective glottic closure reflex, mediated by the superior laryngeal nerve. “With severe Laryngospasm, the false cords and epiglottic body come together firmly.

Airflow is absent, there is no vocal sound, and the true

vocal cords cannot be seen.

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If laryngospasm persists, arterial hypoxemia and hypercapnia will decrease postsynaptic action potentials and brainstem output to the superior laryngeal nerve, and the intensity of the laryngospasm will eventually decrease.

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The most common method of overcoming laryngospasm is continued positive airway pressure applied by faccmask or the intravenous administration of a neuromuscular blocking drug such as succinylcholine(0.25 to 1 mg/kg). Intubation of the trachca may be warranted in selected patients.

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TONSILLECTOMY AND ADENOIDECTOMY

Patients who undergo tonsillectomy and adenoidectomy are usually young and healthy.

Although recurrent upper respiratory tract infection remains a significant indication for surgery, upper airway obstruction, especially during sleep (obstructive sleep apnea [OSA]), accounts for an increasing percentage of the procedures performed,especially in children younger than 4 years.

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Preoperative evaluation for tonsillectomy or adenoidectomy, or both, depends on the initial history and physical examination. In otherwise normal patients who have classic symptoms of severe upper airway obstruction and adenotonsillar hypertrophy, the preoperative evaluation rarely requires any special studies.

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In some patients, if severe airway obstruction is suspected, an electrocardiogram, echocardiogram, chest radiograph, and coagulation studies may be considered. Sedative premedication may be avoided in children with OSA, intermittent upper airway obstruction, or very large tonsils.

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OBSTRUCTIVE SLEEP APNEA

OSA syndrome may be associated with behavior and growth disturbances. Symptoms in these patients include snoring, sleep disturbances and daytime hypersomnolence,

decreased school performance and personality changes, recurrent enuresis, hyponasal speech, and growth disturbances.

Patients with OSA are often obese with potentially difficult upper airway management.

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These individuals will probably have short, thick necks, large tongues, and redundant pharyngeal tissues such that upper airway obstruction is frequent and awake tracheal intubation will be necessary. Polysomnography to evaluate the severity of OSA requires hospitalization, is expensive, and is rarely needed.

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UPPER RESPIRATORY TRACT INFECTIONS

Patients may arrive at the hospital for elective tonsillectomy and adenoidectomy with an acute upper respiratory tract infection. Surgery for these patients is usually postponed until resolution of the upper respiratory tract infection, which is typically 7 to 14 days. Laryngospasm with airway manipulation may be more likely to occur in the presence of an upper respiratory tract infection.

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GASTROESOPHAGEAL REFLUX DISEASE

Gastroesophageal reflux disease (GERD) may be a significant symptom in children with chronic lung

disease or upper airway obstruction (or both) secondary to

increased intrathoracic negative pressure. This is particularly relevant in neurologically abnormal patients (hypotonia, developmental delay) because such patients have a high incidence of GERD even without upper airway obstruction.

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GERD is a consideration in young children with significant developmental delay who require

tonsillectomy to treat upper airway obstruction.

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MANAGEMENTOF ANESTHESIA

Management of anesthesia for patients undergoing tonsillectomy is focused on airway considerations

and bleeding. Continuous positive airway pressure

during induction of anesthesia may be useful for alleviating upper airway obstruction.

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Placement of a cuffed endotracheal tube will decrease the incidence of aspiration of blood. As with an uncuffed tube, a cuffed endotracheal tube should be appropriately sized to allow an air leak around the tube with 20 to 25 cm H20 of peak airway pressure.

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The tracheal tube cuff is inflated beyond this point only if high peak airway pressure is needed to ventilate the lungs adequately or if hemorrhage suddenly develops.

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When difficult tracheal intubation is anticipated, it may be helpful to have an otolaryngologist present.

The use of an oral RAE tube for tracheal intubation may

optimize visualization of the surgical field.

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The supraglottic area may be packed with petroleum gauze to minimize the likelihood of inhalation of blood from the pharynx.

when gauze packing is used, it is important to maintain

an appropriate leak around the tube during the application

of positive airway pressure.

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The practice of monitoring young children for 24 hours after surgery is based on observations of postoperative airway obstruction occurring in children younger than 4 years as late as 18 to 24 hours postoperatively.

In addition to young age, risk factors associated with postoperative airway obstruction after tonsillectomy may include prematurity and recent upper respiratory infection.

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Surgeons are meticulous about ensuring a dry tonsillar bed at the end of surgery and often place a pack in the posterior of the pharynx to limit draining of blood into the stomach during the procedure. Inserting an orogastric tube into the stomach before extubating the trachea

while being careful to not traumatize the adenoidectomy site is a frequent maneuver to remove any blood that may

have drained into the stomach.

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Tracheal extubation is performed when the child is awake and responding. In patients with reactive airway disease, including asthma, tracheal extubation may be performed while the patient is still anesthetized to decrease the likelihood of bronchospasm and laryngospasm.

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POSTOPERATIVE CARE AND COMPLICATIONS

Dexamethasone administered intravenously may be useful for decreasing postoperative pain. Adding an intraoperative dose of an antiemetic and removing

blood from the stomach may combine to decrease

postoperative emesis.

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Hemorrhage from a bleeding tonsil in the postoperative period is a recognized complication. The need for

tracheal reintubation may be complicated by the presence of

large amounts of swallowed blood in the stomach. In this

regard, care should be taken to not oversedate these patients.

If the bleeding is not controlled, the patient should be returned to the operating room for exploration and surgical hemostasis.

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Acute airway obstruction such as laryngospasm can lead to negative-pressure pulmonary edema. This

occurs as the patient breathes against a closed glottis and

negative intrathoracic pressure is created. This pressure is transmitted to interstitial tissue, where the hydrostatic pressure gradient is increased and enhances fluid movement out of the pulmonary circulation into the alveoli. Airway obstruction in the postoperative period can also be associated with retention of a pharyngeal pack.

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Postoperative Complications of Tonsillectomy

• Emesis (occurs in 30%–65% of patients; mechanism unknown but may include the presence of irritant blood in the stomach)

• Dehydration• Hemorrhage (75% occurs in first 6 hours after surgery; if

surgical hemostasis is required, a full stomach and hypovolemia should be considered)

• Pain (minimal after adenoidectomy and severe after tonsillectomy)

• Postobstructive pulmonary edema (rare but possible if the patient has had a prior acute upper airway obstruction; treatment may include supplemental oxygen and administration of diuretics)

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Examples of patients in whom early discharge is not advised after tonsillectomy include those younger than 3 years of age and those with abnormal coagulation values, evidence of obstructive sleep disorder or apnea, presence of a peritonsillar abscess, and conditions (distance, weather, social conditions) that would prevent close observation or prompt return to the hospital.

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LASER SURGERY

Laser surgery provides precision in targeting airway lesions, minimal bleeding and edema, preservation of surrounding structures, and rapid healing. The carbon dioxide laser has particular application in the treatment of laryngeal or vocal cord papillomas, laryngeal webs, resection of redundant subglottic tissue, and coagulation

of hemangiomas.

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In most cases laser surgery is preceded by microdirect laryngoscopy. The use of small-diameter

endotracheal tubes (5.0 or 5.5 mm internal diameter) is

necessary for optimum exposure. Brief skeletal muscle

paralysis as provided by an infusion of succinylcholine

may be useful.

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MANAG EM ENT OF AN ESTH ESIA

Anesthesia during laser surgery may be administered with

or without an endotracheal tube. However, appropriate

laser-resistant endotracheal tubes should be available. In

this regard, all polyvinyl chloride endotracheal tubes are

flammable and can ignite and vaporize when in contact

with the laser beam.

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Some surgeons may prefer using a Dedo or Marshall laryngoscope and intermittent ventilation with a Sanders jet ventilator. The Sanders jet ventilator delivers oxygen at 50 psi directly through a port in the laryngoscope. If a Dedo or Marshall laryngoscope is used, maintenance anesthesia can be accomplished with an

intravenous anesthetic.

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Use of the Sanders jet ventilator is associated with a risk for pneumothorax and pneumomediastinum as a result of rupture of alveolar blebs or a bronchus.

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Laser surgery produces a plume of smoke and particles (mean size, 0.31µm) that can be deposited in the

alveoli if aspirated . This hazard can be minimized if an efficient smoke evacuator and special masks are used. A misdirected laser bean can also lead to perforation of a viscus and transection of blood vessels.

Other risks include venous gas embolism and ocular

injury.

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HAZARDS ASSOCIATED WITH LASER SURGERY

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The patient's eyes must be protected by taping them shut, followed by the application of wet gauze

pads and a metal shield to prevent laser penetration. All operating room personnel should wear special

protective glasses.

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Characteristic signs and symptoms of acute epiglottitis include

(1)a sudden onset of fever, dysphagia, drooling, thick muffled voice, and preference for the sitting position with the head extended and leaning forward

(2) retractions, labored breathing, and cyanosis when respiratory obstruction is present.

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