Airway Management

TABLE 27-5 TECHNIQUES OF COMMON AIRWAY INDEXES MEASUREMENT

Thyromental distance: Measured along a straight line from tip of mentum to thyroid notch in neck-extended position

Mouth opening: Interincisor distance (or interalveolus distance when edentulous) with the mouth fully opened

Mallampati score (see legend, Fig. 27-3)

Head and neck movement: The range of motion from full extension to full flexion

Ability to prognath: Capacity to bring the lower incisors in front of the upper incisors

TABLE 27-6 PRESENCE OF RISK FACTORS AND INCIDENCE OF DIFFICULT INTUBATION

*Presence of upper front teeth, history of a difficult intubation, Mallampati classification >1, Mallampati classification of 4, or mouth opening <4 cm.

a. After induction of anesthesia, the face mask is held firmly on the patient’s face with downward pressure on the mask applied by the anesthesiologist’s thumb and first or second fingers with concurrent upward displacement of the mandible with the other fingers (known as a jaw thrust), which raises the soft tissues of the anterior airway off the pharyngeal wall and allows for improved ventilation.

b. In patients who are obese, edentulous, or have beards, two hands may be required to ensure a tight-fitting face mask. (When two hands are required, a second operator is needed.)

2. In the presence of normal lung compliance, the lung inflation pressure should not exceed 20 to 25 cm H₂O.

a. If more pressure is required, it may be prudent to consider other devices to aid in the creation of a patent upper airway (oral airway, nasal airway, LMA) to create an artificial passage between the roof of the mouth, tongue, and posterior pharyngeal wall.

b. Oral airways may provoke coughing, vomiting, or laryngospasm when placed into the pharynx of a semiconscious patient.

C. Supraglottic Airways. SGAs are associated with a lower incidence of sore throat, coughing, and laryngospasm on emergence compared with tracheal intubation. The advent of the LMA and other SGA devices has led some to question the relative safety of tracheal intubation (vocal cord edema, increased airflow resistance). Pharyngeal mucosal changes as a result of SGA use appear to be delayed compared with the effects of tracheal intubation.

1. The LMA classic is composed of a small “mask” designed to sit in the hypopharynx with an aperture overlying the laryngeal inlet. The rim of the mask is composed of an inflatable silicone cuff that fills the hypopharyngeal space, creating a seal that allows positive-pressure ventilation with up to 20 cm H₂O pressure and tidal volumes of 8 mL/kg.

2. The LMA flexible is designed to permit sharing of the airway with the surgical team (designed to be used with a tonsillar mouth gag) (Table 27-7).

3. The SGA and Bronchospasm. As an SGA, the LMA appears to be well suited for patients with a history of bronchospasm (asthma) who are not at risk for reflux and aspiration.

TABLE 27-7 ADVANTAGES OF THE LARYNGEAL MASK AIRWAY IN SUPRAGLOTTIC SURGERY

Improved protection of the airway from blood and surgical debris

Reduced cardiovascular responses

Reduced coughing on emergence

Reduced laryngospasm after airway device removal

Improved oxygen saturation after airway device removal

Ability to administer oxygen until complete restoration of airway reflexes

4. SGA Removal. The timing of removal of the LMA at the end of surgery is critical. The LMA should be removed when the patient is deeply anesthetized or after protective reflexes have returned and the patient is able to open his or her mouth on command.

5. Contraindications to SGA Use (Table 27-8)

6. SGA Use Complications (Table 27-9)

7. The laryngeal tube consists of a single-lumen tube and two (distal and proximal) low-pressure cuffs. When inserted correctly, the proximal cuff seals the oral and nasal pharynx, and the distal cuff sits within the upper esophageal sphincter.

8. The Double Lumen SGAs (Table 27-10).

D. Tracheal Intubation

1. Direct Laryngoscopy. Successful laryngoscopy involves the distortion of the normal anatomic planes of the supralaryngeal airway to produce a line of direct visualization (“sniff position of the patient’s head”) from the operator’s eyes to the larynx (this requires alignment of the oral, pharyngeal, and laryngeal axes) (Fig. 27-1).

TABLE 27-8 CONTRAINDICATIONS TO USE OF A SUPRAGLOTTIC AIRWAY

Risk of pulmonary aspiration of gastric contents (patient with a “full stomach”)

Hiatal hernia with significant gastroesophageal reflux

Morbid obesity

Intestinal obstruction

Delayed gastric emptying

Poor pulmonary compliance

Increased airway resistance

Glottic or subglottic airway obstruction

Limited mouth opening

TABLE 27-9 COMPLICATIONS WITH USE OF A SUPRAGLOTTIC AIRWAY

Gastroesophageal reflux and aspiration

Laryngospasm

Coughing

Bronchospasm

Sore throat (less than with tracheal intubation)

Transient changes in vocal cord function (possibly related to cuff overinflation during prolonged procedures)

Nerve injury (recurrent laryngeal, hypoglossal, or lingual; LMA cuff pressure should not exceed 60 cm H₂O)

Diffusion of nitrous oxide into the cuff, increasing pressure

LMA = laryngeal mask airway.

TABLE 27-10 FEATURES OF THE LARYNGEAL MASK AIRWAY PROSEAL

*When a small amount of lubricant is used to occlude the gastric drain, gentle pressure on the suprasternal notch is reflected in movement of the lubricant meniscus.

LMA = laryngeal mask airway.

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