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Saturday, June 22, 2019

LARYNGEAL MASK AIRWAY complete note



      LARYNGEAL MASK AIRWAY





The laryngeal mask airway (LMA) is a supraglottic airway device developed by British Anesthesiologist Dr. Archi Brain. It has been in use since 1988. Initially designed for use in the operating room as a method of elective ventilation, it is a good alternative to bag-valve-mask ventilation, freeing the hands of the provider with the benefit of less gastric distention.Initially used primarily in the operating room setting, the LMA has more recently come into use in the emergency setting as an important accessory device for management of the difficult airway.


The LMA is shaped like a large endotracheal tube on the proximal end that connects to an elliptical mask on the distal end. It is designed to sit in the patient’s hypopharynx and cover the supraglottic structures, thereby allowing relative isolation of the trachea. The patient should be obtunded and unresponsive before one of these devices is placed.


The LMA is a good airway device in many settings, including the operating room, the emergency department, and out-of-hospital care, because it is easy to use and quick to place, even for the inexperienced provider.A success rate for placement of a LMA of nearly 100% occurs in the operating room. A lower rate of achievement for LMA placement may be expected in the emergency setting.Its use results in less gastric distention than with bag-valve-mask ventilation, which reduces but does not eliminate the risk of aspiration.This may be particularly pertinent in patients who have not fasted before being ventilated.


Laryngeal mask airways come in several types, as follows:


A... The LMA Classic is the original reusable design
B. .. The LMA Unique is a disposable version, making it ideal for emergency and prehospital settings
 C  LMA Fastrach, an intubating LMA (ILMA), is designed to serve as a conduit for intubation. Although most LMA designs can serve this purpose, the LMA Fastrach has special features that increase the rate of successful intubation and do not limit the size of the endotracheal tube (ETT). These features include an insertion handle, a rigid shaft with anatomical curvature, and an epiglottic elevating bar designed to lift the epiglottis as the ETT passes.

D.. .. The LMA Flexible has softer tubing. It is not used the in the emergency setting.

E.. .. Another newer design is the LMA CTrach, which inserts like the LMA Fastrach and has built-in fiberoptics with a video screen that affords a direct view of the larynx.

Indications

Elective ventilation



The laryngeal mask airway (LMA) is an acceptable alternative to mask anesthesia in the operating room. It is often used for short procedures when endotracheal intubation is not necessary.

Difficult airway


After failed intubation, the LMA can be used as a rescue device

In the case of the patient who cannot be intubated but can be ventilated, the LMA is a good alternative to continued bag-valve-mask ventilation because LMA is easier to maintain over time and it has been shown to decrease, though not eliminate, aspiration risk


In the case of the patient who cannot be intubated or ventilated, a surgical airway is indicated and should not be delayed. However, if the LMA is at hand, it can easily be attempted quickly, while an assistant simultaneously prepares for cricothyroidotomy



Cardiac arrest

The 2005 American Heart Association guidelines indicate the LMA as an acceptable alternative to intubation for airway management in the cardiac arrest patient .This may be particularly useful in the prehospital setting, where emergency medical technicians typically have less experience with intubation and lower success rates.


Conduit for intubation

The LMA can be used as a conduit for intubation, particularly when direct laryngoscopy is unsuccessful.


An ETT can be passed directly through the LMA or ILMA. Intubation may also be assisted by a bougie or fiberoptic scope

Prehospital airway management

The LMA is useful in the prehospital setting not only for patients in cardiac arrest but also for managing a difficult airway.

In patients in whom positioning or prolonged extrication does not allow for endotracheal intubation, the LMA can be inserted and allow for successful airway management until a definitive airway can be established


The widespread use of LMA in the prehospital setting in Japan for cardiac arrest has shown it to be an effective and relied upon method for establishing emergency airways


Contraindications

Absolute contraindications (in all settings, including emergent) are as follows:

A- Cannot open mouth

B- Complete upper airway obstruction

Relative contraindications (in the elective setting) are as follows:

1- Increased risk of aspiration: Prolonged bag-valve-mask ventilation, morbid obesity, second or third trimester pregnancy, patients who have not fasted before ventilation, upper gastrointestinal bleed

2- Suspected or known abnormalities in supraglottic anatomy

3- Need for high airway pressures (In all but the LMA ProSeal, pressure cannot exceed 20 mm water for effective ventilation.)

Anesthesia

Laryngeal mask airway (LMA) insertion is facilitated by sedation. Propofol (Diprivan) or midazolam (Versed) are acceptable choices. For elective ventilation in the operating room, less anesthesia is typically required for insertion and maintenance of the LMA than for endotracheal intubation. In the emergency setting, the patient is often obtunded or unconscious, and further sedation may not be necessary for LMA insertion. The risk of inadequate sedation is triggering laryngospasm

Paralysis is not necessary for LMA insertion and maintenance.

Movement and coughing upon insertion should be particularly avoided in patients who are at risk for cervical spine injuries; therefore, adequate anesthesia is particularly important in these patients.

Equipment



Laryngeal mask airway (LMA),

Appropriately sized syringe for cuff inflation (included in LMA kit)

Water-soluble lubricant (included in LMA kit)

Bag-valve mask

Oxygen source

Yankauer suction device

End-tidal carbon dioxide (E CO) detector

Intubation equipment and a cricothyroidotomy kit (These items should be close at hand.)

Positioning

The optimal head position for insertion of the laryngeal mask airway (LMA) is sniffing position.

The optimal head position for insertion of the intubating laryngeal mask airway (ILMA) is neutral position

Technique


Preparation

Preoxygenate the patient with 100% oxygen via a nonrebreather mask, as time allows.

Choose the appropriate size of laryngeal mask airway (LMA).

Check the LMA cuff for leaks.


Deflate the cuff of the LMA completely against a flat surfacesurface
Apply a water-soluble lubricant generously to the posterior surface of the mask.

Administer sedation when indicatedp

Position the patient.


Insertion of the LMA

Hold the LMA like a pen, with the index finger of the dominant hand at the junction of the mask and the tube, as shown below.

Slide the LMA along the hard palate, pushing it back against the palate as it is advanced toward the hypopharynx, as in the image below. This prevents the tip from folding over on itself and reduces interference from the tongue.

Advance with gentle pressure until resistance is met.

If necessary, continue pressure on the tube with the nondominant hand to fully advance the LMA to its proper position.

Once in place, inflate the cuff without holding the LMA to allow it to acquire its natural position.

Approximately 8 cm of the tube protrudes from the patient’s mouth.

Slide the mask backward, following the curve of the tube.

Swing the ILMA into place.
Inflate the cuff as with the LMA.



Confirming placement

Confirm the position of the LMA by auscultating bilateral breath sounds and an absence of sounds over the epigastrium, observing chest rise with ventilation, and placing an E CO to look for color change.

Ensure that the vertical black line on the tube is at the patient’s midline.
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