1. Using the Laryngeal Mask Airway
Norman L. Goody, MD

2. Objective Using the LMA LMA and the Difficult Airway
LMA and Pediatric Anesthesia
LMA and OB Anesthesia
Advantages of Using the LMA
Disadvantages of the LMA
Complications Arising from Use of the LMA
Contraindications to Using the LMA

3. History of the LMA
development began in 1981 at Royal London Hospital by Dr. Archie Brain
modification of the Goldman Dental Mask
available commercially in UK since 1988 and in the US since 1992
now used in >50% of general anesthetics in some centers in UK (and probably US, too- especially ambulatory surgery)

4. Characteristics of the LMA
Latex free, medical-grade silicone
Aperture bars
Sizes
# <6.5 kg ml
# kg ml
#2 1/ kg ml
# kg ml
# kg ml
latex free
aperture bars prevent epiglottis from occluding the lumen y holding it out of the way
Only metal part is a spring in the valve
“metal-free” version available for use in MRI

5. Using the LMA Preparation of the LMA Induction Insertion of the LMA
Check patency of cuff- flexing LMA 180’ should not kink shaft
fold cuff BACK smooth- away from aperture. Cuff should be flat w/ no wrinkles
Cuff has “memory”
Lubricate POSTERIOR surface only
Surgilube v. lidocaine jelly (which contains preservatives-->sore throat/allergic rxn)
Induction
insertion requires depth similar to that which allows placement of oral airway
propofol (2-2.5 mg/kg)v. STP (then deepen w/ inhaled) Etomidate not recommended
Insertion of the LMA
1st- “sniffing position”
2 techniques to hold LMA- describe “hold like pencil then advance w/ index finger” using index finger to guide tube over the back of the tongue
while stabilizing head w/ other hand-THEN GIVE MY TECHNIQUE
place tip of LMA against hard palate under direct vision
then, advance in one smooth movement until characteristic resistance is felt, which is upper esophageal sphincter
if initial resistance-STOP- reposition against the hard palate
immediately after insertion, LET GO and inflate the cuff. You should see characteristic outward movement of LMA as it centers itself around the laryngeal inlet
with IPPV an audible leak at cm H2O is common (which often disappears as hypopharyngeal mucosa molds around cuff perimeter
HAS BEEN USED IN CASES UP TO & HOURS DURATION
Securing
secure neutral or straight down chin
do not bend upwards
use black line on tube as a visual check of position/orientation
secure and protect against biting- can use rolled gauze sponges
NEVER cut the tube
Common Problems-
if tip is not against hard palate, LMA may roll and fold on itself or roll up and jam against epiglottis
other techniques:
rotational movement, jaw thrust, bowl posterior or can use laryngoscope
if too light
laryngeal spasm/coughing/straining/breath holding/swallowing
RX BY DEEPENING ANESTHETIC- by inhal or IV-REMOVING USUALLY MAKES IT WORSE! (MORE STIMULATION)
too much air in the cuff will reduce the compliance of the cuff to form to the laryngeal inlet- it does not improve the seal
N2O will diffuse into cuff over time (as short as 30”)
CRICOID PRESSURE-increase angle of axes btwn LMA/trachea
Preparation of the LMA
Check patency of cuff
Lubricate POSTERIOR surface only
Surgilube v. lidocaine jelly
Induction
Insertion of the LMA
Common Problems
Cricoid Pressure
Securing the LMA

6. Using the LMA Maintenance of Anesthesia Removal of the LMA
Cleaning, Sterilization and Re-use
Maintenance
do not use forceful bag squeezing, though slight (+) pressure is OK
(give my opinion of spont vent) Forane or Sevo
Removal
remove when mouth opened on request
do not ;leave syringe attached to valve, as premature deflation of balloon may occur
watch for swallowing as an indication of returning airway reflexes
Cleaning
clean w/ warm water and bottle brush to remove all secretions/deposits
cuff should be FULLY DEFLATED before autoclaving
autoclave ” for at least 3 minutes
manufacturer guarantees 10 uses. some reports of >250 uses
AVOID FORCEFUL REMOVAL OF THE DEVICE THROUGH A PARTIALLY OPENED MOUTH (life span goes way down)

7. Determining Life Span of LMA
intended for uses, but highly over-manufactured
tube remains translucent
aperture bars remain intact
cuff deflates correctly
no valve leakage
cuff remains symmetric
pilot balloon retains shape
connector remains tight/ not broken
reported as many as 250 uses

8. THE LMA IS NOT DISPOSABLE

9. LMA and the Difficult Airway
Awake Intubation
Difficult MASK Airway
Blind Intubation
Failed Intubation
Fiberoptic Bronchoscopy and the LMA
Emergent Intubation by an Unskilled Provider
Awake Intub:
can topicalize pt. and place awake.
Difficult mask
b/c of beard, large/small mandible, redundant tissue/big tongue
Blind:
distal aperture of LMA sits directly over the laryngeal inlet
can pass an uncut, lubricated 6mm cuffed ETT through the mask
rotate tube 90’ to left (CCW) during passage to bring bevel anterior to pass through aperture bars
one study showed 72% success in avg 13 sec. and additional 12% after re-adjust. Later study by same author -->90% success w/ blind
can also used a soft ETT changer (gum-rubber bougee)
Failed:
per Dr. Brain, LMA may be easier to insert when larynx is anterior (when tracheal intubation is most difficult)
try before crich. low risk/benefit ratio per Benumof.
full-stomach pt controversial
cricoid pressure may make placement more difficult
FOB: 5.0mm FOB will fit through #4
can be used as above in awake placement, or asleep. FOB can be used and then ETT passed over OR wire can be passed through suction port and used as a guidewire
Unskilled: 2 studies: personnel w/ no previous experience using the LMA were successful in 90+% of cases
NOT USEFUL IF PT HAS LIMITED MOUTH OPENING

10. LMA and Pediatric Anesthesia
DL&B
tracheal stenosis
difficult airway
greater anesthetic depth is required in a child than when inserting an oral airway
recommended that LMA only be inserted in spontaneously breathing children
breath holding and laryngospasm may be mistaken for incorrect position but usually result from inadequate anesthesia
intubation through LMA in children always preceded by FOB inspection b/c epiglottis can be folded down or included in bowl of mask

11. Accuracy of End-tidal CO2 in Pediatrics using LMA
22 children, mechanically ventilated to a stable ETCO2
ventilation via the LMA
mean ETCO2 and PaCO2 obtained were /- 3.3 and /- 9.09, respectively
ventilation via ETT
mean ETCO2 and PaCO2 obtained were /- 2.9 and /- 5.25, respectively
LMA ETCO2 is as accurate an indicator of PaCO2 as when ventilated via ETT
Anesth Analg Feb;82 (2) :247-50
Study was done to observe correlation between end-tidal and arterial carbon dioxide during controlled ventilation via LMA
in other words, the LMA can be used in pediatric anesthesia and the ETCO2 can be considered to be an accurate reflection of the underlying PaCO2 with about a difference of about 4 mmHg

12. LMA and OB Anesthesia Questionnaire to 250 anesthesiologists in the UK
LMA was available in 91.4% of obstetric units
72% were in favor of using LMA for failed intubation with inadequate ventilation via face mask
24 had experience with LMA in such a situation, 8 of which stated that LMA had proved to be a “lifesaver”
Authors believed that we should use LMA before cricothyroidotomy for failed intubation/ventilation
Can J Anaesth Gataure, et al Feb;42(2):130-3
250 anesthesiologists asked to fill out questionnaire regarding views of LMA in OB anesthesia

13. Advantages of Using the LMA
Meta-analysis comparing advantages of the LMA over the tracheal tube or face mask
Reviewed 858 LMA publications identified to December 1994, of which 52 met criteria for analysis
32 different issues were tested
Can J Anaesth Brimacombe 1995 Nov;42(11):
Study from the Dept. of anesthesia, Cairns Base Hospital, Australia

14. Advantages of LMA over ETT
increased speed and ease of placement by inexperienced personnel
increased speed of placement by anesthetists
improved hemodynamic stability at induction and during emergence
minimal increase in intraocular pressure following insertion
Can J Anaesth Brimacombe 1995 Nov;42(11):

15. Advantages of LMA over ETT
reduced anesthetic requirements for airway tolerance
lower frequency of coughing during emergence
improved oxygen saturation during emergence
lower incidence of sore throats in adults
Can J Anaesth Brimacombe 1995 Nov;42(11):

16. Advantages of LMA over Face Mask
easier placement by inexperienced personnel
improved oxygen saturation
less hand fatigue
improved operating conditions during minor pediatric otological surgery
Can J Anaesth Brimacombe 1995 Nov;42(11):

17. Additional Advantages of Using the LMA
leaves provider’s hands free
patient can produce effective cough
allows spontaneous ventilation
even malpositioned can adequately ventilate
Sore Throat- less than ETT and FM
Leaves Provider’s Hands Free
Better tolerated than ETT
Better than Face Mask
even malpositioned, can still usually ventilate
Pt can produce effective cough even w/ LMA in place
allows spontaneous ventilation
Minimal CV Response- probably due to lack of direct laryngeal and tracheal stimulation

18. Disadvantages of LMA over the ETT
lower seal pressure
higher frequency of gastric insufflation
Can J Anaesth Brimacombe 1995 Nov;42(11):

19. Disadvantages of LMA over the FM
esophageal reflux more likely
Can J Anaesth Brimacombe 1995 Nov;42(11):
Additionally-
cough and laryngospasm can still occur, but usually if LMA is inserted with inadequate anesthesia

20. Contraindications to Using the LMA
Full Stomach
Non-fasted
34+ week pregnant
trauma
acute abdomen
thoracic injury
opiate premedication
autonomic neuropathy
patient unable to follow instructions
any condition known to delay gastric emptying

21. Contraindications to Using the LMA
Full Stomach
Patients with a history of GE reflux

22. Contraindications to Using the LMA
Full Stomach
Patients with a history of GE reflux
Patients with low pulmonary compliance needing positive pressure ventilation

23. Complications Arising from Use of the LMA
Aspiration
a study looking at DENTAL surgery:
blood was visible within the bowl of the mask after its removal in only 3% of 223 cases

24. Passive Regurgitation and the LMA
Study looked at gastric regurgitation during GA in different positions with the LMA
15 minutes before induction, patients swallowed a 75 mg methylene blue capsule.
supine, Trendelenburg and lithotomy positions
post-op, LMA and oropharynx were inspected for bluish discoloration
No blue dye was detected in the supine group but it was observed in one patient in each of the other two groups
Anaesthesia Strong, et al Dec;50(12):1053-5
this study only demonstrates that gastric fluids may come into contact w/ the cuff via passive reflux-
THIS WOULD BE PRESUMED TO ALSO OCCUR W/ AN ETT IN PLACE
it says nothing about ACTUAL significance of these findings
the real issue is “does the LMA prevent passive passage of fluids in the hypopharynx into the lungs?”
when looking at the anatomy of the hypopharynx, it should be noted that even with the LMA in place, there is an anatomic channel by which fluids MAY bypass the protection afforded by the cuff.
it is possible for fluids to leak via the pyriform fossa.
Despite this potential for aspiration, there are not case reports nor studies to indicate that aspiration has been a problem w/ the LMA when it is used correctly and appropriately

25. Passive Regurgitation: LMA v. ETT
Study at UT Dallas comparing incidence of reflux for spontaneously breathing anesthetized patients with either an ETT or LMA by continuous measurement of hypopharyngeal pH
“Continuous monitoring...failed to detect evidence of pharyngeal regurgitation.”
Anesth Anal Joshi, et al Feb;82(2):254-7
60 pts.
standardized technique
pH electrode was placed in the hypopharynx and pH values were continuously collected.
no episodes of hypopharyngeal regurgitation (pH<4) were detected during the course of measurement
at no time did hypopharyngeal pH decrease below 5.5
median values 5.7 and 6.2 w/ LMA and ETT. respectively
pH in any given pt did not vary more than 1 unit from initial value recorded at start of operation

26. Complications Arising from Use of the LMA
Aspiration
Coughing

27. Complications
Incidence of airway complications following GA using either ETT or LMA
Significantly greater incidence of coughing PRIOR to extubation, AT extubation and AFTER extubation in the ETT group than in the LMA group
No airway complications were seen in either group
JR Soc Med Denny, et al Sep;86(9):521-2
study from UK
prospective, randomized study of 79 pts undergoing cataract surgery
assessment made at extubation and for 25 min afterwards

28. Complications Arising from Use of the LMA
Aspiration
Coughing
Sore Throat

29. Sore Throat
incidence of sore throat looked at in 327 patients who had GA
mild/moderate soreness
7% of patients with LMA
10% who had FM and oral airway
47% of had ETT
24 hours later, 3% of intubated group still c/o severe soreness, while NONE of the other patients had any c/o
SEE ABOVE
another study looked at 321 pts
mild/moderate soreness in 7% with LMA
10% FM and oral airway
47% of ETT

30. Other Uses for the LMA Bronchoscopy “Big MAC” Oral Surgery
Head and Neck Surgery
Professional Singers
Laparoscopic Surgery?
Bronchoscopy
big MAC
oral
ENT- can do T&A: protects larynx from blood- makes throat pack unnecessary. quiet recovery w/ minimal coughing
also good for ophthalmic surgery
singers-fewer voice changes
MRI-
laparoscopic surgery: “yes” for gyn laps- especially with new, lower pressure insufflators, “probably no” for lap chole- based on anecdotal evidence

31. Conclusions Many advantages over ETT and FM
Useful in many areas of anesthesia care
Especially useful in outpatient anesthesia
Safe when used appropriately

32. Take Home Message routinely test the cuff before use
avoid lubricating the anterior surface of the mask
only insert the LMA when an adequate depth of anesthesia has been obtained
maintain an adequate anesthetic depth throughout surgery
avoid disturbing the patient during emergence
keep the cuff inflated until the patient is awake