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Note: Because of the multitude of differences in clinical application and placement technique among the LMA Classic, LMA Flexible, and LMA ProSeal and LMA Fastrach, this chapter shall deal only with use of the LMA Classic.
- Airway management for general anesthesia with and without spontaneous ventilation
- Rescue airway after failed intubation or ineffective mask ventilation
- Facilitation of endotracheal intubation
- Situations in which airway control is desirable, but tracheal intubation may be difficult or contraindicated:
- Patients trapped in a sitting position
- Suspected cervical spine trauma
- Inability to extend or rotate the cervical spine due to congenital or acquired abnormalities
- Severe rheumatoid arthritis or osteoarthritis
- History of cervical spine fusion
- History of atlantoaxial dislocation
- Patients with Down syndrome
Relative Contraindications
- Increased aspiration risk
- Full stomach
- Intestinal obstruction
- Severe gastrointestinal reflux disease
- Diabetes with gastroparesis
- History of significant peptic ulcer disease
- History of gastric bypass or gastric stapling operation
- Pregnancy, particularly second and third trimester
- Significantly reduced pulmonary compliance
- Major trauma to maxilla, mandible, or larynx
- Unstable cervical spine
- Unusual operative positioning; particularly prone position
- Major intrathoracic surgery
- Major intraabdominal surgery
- Morbid obesity or patients requiring high inspiratory pressures for ventilation
- Tracheoesophageal fistula
- Equipment for mask ventilation
- Emergency medications, supplies, and equipment for intubation
- Disposable or reusable LMA Classic
- Lubricating jelly
- Clean, dry syringe for cuff inflation/deflation
- Tape to secure LMA after placement
- Soft bite block
Placement of the LMA involves passage through the open oral cavity, along and against the hard and soft palate, around the curve of the palatopharyngeal junction, underneath the tongue, and past the epiglottis and tonsillar pillars. When properly positioned the distal cuff of the LMA sits in the hypopharynx just proximal to the upper esophageal sphincter, with the opening of the bowl directed over the glottic opening. During placement, the natural anatomic curves of the oral cavity and the palatopharynx are used to guide the LMA into place. Ideally, the inflated cuff makes a seal with but does not compress the arytenoid cartilages surrounding the glottis.
Large tongue, small interincisor distance (mouth opening), and large floppy epiglottis may make optimal LMA positioning more difficult. Neck flexion and cricoid pressure also serve to reduce the cross-sectional palatopharyngeal area available for manipulation during placement.
Several types of malpositioning of the LMA are common. These include (1) a "flipped tip," with the distal cuff inverted during insertion; (2) entrapment and resulting folding of the epiglottis over the airway by the distal cuff; (3) sideways rotation during placement; (4) overadvancement through the upper esophageal sphincter; (5) underadvancement into the oropharynx; and (6) anterior advancement into the glottic opening.
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Figure 1
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Different versions of LMAs. From left to right, LMA Pro-seal with gastric drainage port, LMA classic, LMA Fast-Trac with endotracheal tube and advancing stylet, disposable LMA.
Figure 2
:
Features of the pharynx demonstrating relative positions of the tongue, epiglottis, laryngeal inlet, transverse arytenoid cartilages, esophagus, and trachea. From Drake L, Vogl AW, Mitchell AWM, Tibbitts RM, Richardson PE: Gray's Atlas of Anatomy. Philadelphia, Elsevier, 2008, p. 504)
Figure 3
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LMA in proper position over the anatomic structures of the hypopharynx and laryngeal opening.
Figure 4
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Common LMA malpositions. In the upper right, there is proper positioning of the LMA over the glottic opening. In the upper left, the LMA is too high in the posterior pharynx, leaving an incomplete seal over the laryngeal opening. In the lower left, the LMA has been advanced into the laryngeal vestibule, partially obstructing the trachea. In the lower right, the LMA has folded back on itself.
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