Laryngeal Mask Airway
Laryngeal Mask Airway
It is an alternative to mask ventilation during a general anesthetic (Figure 5.13 and 5.14). The laryngeal mask airway does not protect against aspiration of gastric contents.
The Advantages of a Laryngeal Mask Airway Include
- Technically easier to insert and less traumatic to the patient when compared to intubation.
- Provides for easier ventilation when compared to a general anesthetic with a mask.
- Can be used as an emergency airway during failed intubation and a guide for endotracheal intubation (Figure 5.14).4.
- The LMA can be used to guide a stylet or bougie, into the trachea and after bougie placement is confirmed, the LMA can be withdrawn and the tracheal tube inserted over the catheter.
- Endotracheal tube may be inserted through LMA in difficult cases
The laryngeal mask airway should not be used in the following situations:
- Emergency surgery in patients who have eaten recently.
- Obese patients
- Any patient who may have delayed emptying of the stomach (i.e. pregnancy).
- Pulmonary diseases such as pulmonary fibrosis. The patient will have poor lung compliance from a stiff lung, requiring high ventilation pressures.
- Should not be used for surgical positions other than supine
Complications related to the use of the laryngeal mask airway include:
- Aspiration
- Sore throat
- Tongue numbness or cyanosis. Ensure that the tongue is not trapped between the teeth and the laryngeal mask airway.
- Laryngospasm: Induce general anesthesia as you would for any other general anesthetic. If the patient is not rendered unconscious or administered a light anesthetic, a laryngospasm may occur.
Table 5.1 Laryngeal Mask Airway Size Based on Patient Weight
| LMA Size | Patient Size and Wright | Maximum Air for Cuff Inflation |
|---|---|---|
| 1 | Neonates and infants (up to 5 kg) | 4 ml |
| 2 | Infants and children (10-20 kg) | 10 ml |
| 3 | Children (30-50 kg) | 20 ml |
| 4 | Small Adults (50-70 kg) | 30 ml |
| 5 | Adults (70-100 kg) | 40ml |
A. The LMA is held by the index finger and the thumb facing the bowl of LMA caudally toward the larynx. The index finger is positioned between the shaft of the LMA and the deflated cuff. The occiput is stabilized with left hand.
B. The deflated and lubricated LMA is placed into the open mouth pressed against the hard palate.
C. The LMA is advanced behind the tongue and into the oropharynx using the index finger.
D. The LMA is pushed further down deep into the hypopharynx using the tip of the index finger.
E. The index finger is removed. The LMA is pushed farther down to its final position by holding the tube of the LMA with the left hand. Without holding the tube of the LMA, the cuff is inflated with the recommended volume of air. The LMA may protrude slightly on inflation of the cuff. Final position of the LMA with cuff inflated. A bite block made of sponges is placed between molars and taped to the LMA tube to prevent patient biting.
Steps for Laryngeal Mask Airway Insertion: Figure 5.15
- Attach an empty syringe to the valve. Fill the laryngeal mask airway with air, ensuring that it inflates. Ensure there are no leaks or bulges in the cuff.
- Remove all the air from the cuff, making it flat. Place a water soluble lubricant to the posterior portion of the cuff. If the lubricant is placed on the anterior surface, it may obstruct the outlet of the laryngeal mask airway.
- Pre-oxygenate the patient and induce general anesthesia. Once the patient is induced, open the patient's mouth, and hold the laryngeal mask airway like a pen. Press the tip of the cuff against the hard palate, inserting the laryngeal mask airway into the hypopharynx until it meets resistance.
- Inflate the laryngeal mask airway until there is an adequate seal (Table 5.1). Do not put more than the maximum recommended amount of air into the cuff. Connect the laryngeal mask airway to the anesthesia circuit. Auscultate lung sounds, ensuring that they are equal and bilateral. If there is any difficulty in ventilation, deflate the cuff and reposition.
- A bite block is placed to prevent the patient from biting down on the laryngeal mask airway. A bite block is usually created by rolling up 4x4cm bandage or gauze and placing it between the teeth. An oral airway will not work.
- At the conclusion of the anesthetic, allow the patient to awaken. The patient should be able to follow commands and open their mouth, allowing the removal of the laryngeal mask airway. Ensure that the patient is breathing adequately before removing the laryngeal mask airway.
Technique of Removal of LMA
After surgery leave the laryngeal mask in place until the patient responds to verbal commands. The cuff does not require to be deflated before removal. Patients, as they awaken, can be encouraged to remove their own laryngeal masks.