Should patients having ambulatory surgery be tracheally intubated?
Whether ambulatory patients have increased gastric volumes when compared with inpatients scheduled for surgery is now questionable. In view of the small incidence of documented aspiration with subsequent major pul-monary derangements in previously healthy patients pre-senting for elective surgery, routine tracheal intubation of every patient is not required. Tracheal intubation should be reserved for patients with any of the known risk factors that predispose patients to esophageal reflux or increased resting gastric volume. Of course, if the surgical procedure requires that the airway must be shared with the surgeon or where an airway cannot be easily or safely maintained using an oropharyngeal or nasopharyngeal airway, tracheal intuba-tion should be performed.
The laryngeal mask airway (LMA), approved by the Food and Drug Administration (FDA) for use in 1991, has proven its value in both the inpatient and ambulatory sur-gery settings. It is presently manufactured in five sizes and is appropriate for the adult patient as well as the neonate. After induction of general anesthesia, the LMA is inserted blindly into the pharynx. Deep anesthesia is necessary for placement of the device. After inflation of the cuff, forma-tion of a low-pressure seal allows both positive pressure as well as spontaneous ventilation. After recovery of normal reflexes, and when the patient is able to respond to com-mands and open the mouth, the device can be gently removed from the oral pharynx.
When properly placed, the LMA can free both hands of the anesthesiologist for other tasks including proper main-tenance of the anesthetic record, adjustment of monitors, and other responsibilities. The incidence of sore throat fol-lowing LMA use is less than that associated with tracheal intubation. Because muscle relaxants are not required for the insertion of the instrument, postoperative myalgias associated with the administration of succinylcholine can be avoided. Additionally, ocular and oral trauma associated with conventional facemasks and oral airways may be avoided. Edentulous patients, characteristically more difficult to ventilate by facemask, can be managed well with this device. Because the LMA does not interfere with the func-tioning of the larynx and glottic closure, an effective cough is possible with the airway in place.
Aspiration of gastric contents has been reported in conjunction with this device. It does not guarantee airway protection. However, in the event of a difficult airway where a patient cannot be intubated and facemask ventila-tion proves to be inadequate, the LMA may serve as a temporizing measure. Contraindications include oral pathology, pulmonary disease marked by low compliance, inability to open the mouth adequately, and conditions that may predispose the patient to gastric reflux.