Discussions for Module 1 : Laryngeal Mask Anesthesia

Questions are answered by module author: John Doyle MD Ph.D. FRCPC

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Question:

Dr. Doyle, The theoretical concern for using the LMA for prone cases is just that, theory. It is time to disprove that theory. I have personally done over 200 prone general anesthetics with the LMA without incident. In my opinion, it is much safer to have a breathing patient in the prone patient than a paralyzed one should the tube fall out. Also the avoidance of the difficult airway algorithm should be everyone's priority. Avoiding muscle relaxants and intubation do just that. It is time for an aspiring academic to disprove the safety concerns for the LMA and the prone position.

 

Dr. Doyle replies:

I believe that the we are undergoing climate change on the matter of using the LMA for prone cases as clinical experience such as yours accumulates. Still, I would suggest that clinicians avoid  attempting using the LMA for prone cases  until they have mastered its use in supine cases.

Question:

What type of LMA was use in the prone position and was there any study to compare between LMA classic versus Pro seal in the prone position?

 

Dr. Doyle replies:

Only a small number of reports on the use of LMAs in the prone position  exist; as a rule the practice is discouraged because of theoretical  safety concerns. 

In one report [1] the LMA Supreme was used. This report includes references to other uses of the LMA in the prone position.   I am not aware of any study comparing the LMA claasic and the LMA ProSeal in the prone position. 

Reference [1] Link 

Question:

is it possible to use proseal for thoracic surgery?

 

Dr. Doyle replies:

Because thoracic surgery typically requires a double lumen tracheal tube or use of a bronchial blocker, a supraglottic airway device like the Proseal LMA would not ordinarily be appropriate, at least not for the entire case. In addition, thoracotomy patients are often operated on in the lateral position, a position somewhat unfavorable to the use of supraglottic airway devices. 

On the other hand, thoracic surgeons often perform fiberoptic bronchoscopy (FOB) before thoracotomy procedures; this allows FOB visualization of the epiglottis, larynx, and entire trachea. Fearson et al. (1997) assessed the LMA as an alternative to a single-lumen ETT for FOB before thoracotomy and found it to be quite satisfactory in this setting.

Ferson DZ, Nesbitt JC, Nesbitt K, Walsh GL, Putnam JB Jr, Schrump DS, Johansen MJ, Jones RL, Roth JA. The laryngeal mask airway: a new standard for airway evaluation in thoracic surgery. Ann Thorac Surg. 1997 Mar;63(3):768-72. PubMed PMID: 9066399.

Question:

Shall I know when to check cuff pressure under anaesthesia.

March 2, 2010 12:02:25 AM, S.A.

Dr. Doyle replies:

According to a European study (European Journal of Anaesthesiology, 2004, vol. 21, no7, pp. 547-552) LMA cuff pressures should be monitored during nitrous oxide anaesthesia when LMA-Classic(r) is used but to do so is of less importance when using the disposable Soft Seal(r) laryngeal mask. Haldar and Immanuel recommend that LMA cuff pressures should be monitored routinely when an LMA is used (Abstract A1720, ASA meeting, October 22, 2008). LMA cuff pressure can be measured using a hand-held Portex pressure gauge. Pressures should be kept under 60 mm Hg.

Question:

Using a Proseal LMA, properly fitted, what pressure can you ventilate to before leak occurs?

Feb. 7, 2009 5:03:12 AM, S.M.

Dr. Doyle replies:

The LMA North America Web site provides the following information on this question: "This reusable airway has a cuff that is made of a softer material than the LMA Classic™ and is designed to conform to the contours of the hypopharynx. While the LMA ProSeal™ may be used with spontaneously breathing patients, it is designed for use with PPV, with and without muscle relaxants. The maximum airway seal pressure will vary between patients, but is on average 50% higher than the LMA Classic™ or up to 30 cm H20."

Question:

Do you advocate the routine use of P-LMA in obstetrics patients who require general anesthesia?

Dec. 12, 2008 9:42:39 PM, A.P.

Dr. Doyle replies:

No. The standard of care in Canada and the USA is to intubate these patients.

Question:

How do you compare the use of classical LMA with the LMAproseal in the overweight/obese patient? My own experience has led me to reach for the LMAproseal everytime, in short procedures, such as breast surgery, when I electively ventilate and thus avoid intubation.

June 29, 2008 at 7:03 AM, D.S.

Dr. Doyle replies:

The ProSeal LMATM is generally held to be a more appropriate choice of LMATM than the LMA ClassicTM in obese patients. As noted by Cooper [1], obese patients "are more likely to have reduced thoracic compliance, increased inspiratory resistance and are commonly believed to be at greater risk of regurgitation". Thus the advantage of the PLMA in this setting "is that allows for ventilation with higher airway pressures and potentially less gastric insufflation".

About 5 years ago Maltby and co-workers [2] presented a study that compared the safety of the LMA and the ETT as an airway during gynecologic laparoscopic surgery, in non-obese and obese (BMI > 30 ) patients. The LMA Classic (LMA-C) was used for the non-obese patients and the ProSeal LMA (PLMA) was used for the obese. Of interest, they did not exclude patients with a history of gastroesophageal reflux or hiatus hernia if their symptoms were controlled at the time of the study. They found that oxygenation and ventilation were comparable whether the airway was secured with an ETT or a LMA. Still, this study raised concerns in some circles. For instance, expresssing a concern about possible regirgitation and aspiration, Cooper noted that while the LMA "has an impressive safety record" we must "be certain that we are not compromising patient safety by using the LMA because it can be used, rather than should be used [1].

For an indepth discussion, I recommend a review by Cook et al. [3]

References:

[1] Cooper RM. The LMA, laparoscopic surgery and the obese patient - can vs should. Can J Anesth 2003; 50: 5–10. Available online at http://www.cja-jca.org/cgi/content/full/50/1/5

[2] Maltby JR, Beriault MT, Watson NC, Liepert DJ, Fick GH. LMA-ClassicTM and LMA-ProSealTM are effective alternatives to endotracheal intubation for gynecologic laparoscopy. Can J Anesth 2003; 50: 71–7. Available online at http://www.cja-jca.org/cgi/content/abstract/50/1/71

[3] Cook TM, Lee G, Nolan JP. The ProSeal laryngeal mask airway: a review of the literature. Can J Anesth 2005; 52: 739–60. Available online at http://www.cja-jca.org/cgi/content/abstract/52/7/739

Question:

What's the maximum duration of surgery that LMA are used? At our institution we routinely use LMA classic or proseal with controlled ventilation for brachial plexus injury _exploration. We don't use muscle relaxant to aid in nerve stimultion during surgical dissection. Propofol infusion was used in all cases. In one case the duration of surgery was 7 hours with LMA classic.

Feb. 18, 2007 at 16:56, P.V.

Dr. Doyle replies:

The LMA website provides some useful information on this topic. (Quoted from their website FAQ)

LMA-Classic™, LMA-Flexible™, LMA-Unique™, & LMA-ProSeal™

The maximum duration for which an LMA™airway can safely be used is not yet known; however, there is increasing evidence that the LMA™ airway may be safe for elective procedures in healthy patients lasting 4 to 8 hours in the hands of experienced users. If the LMA™ airway is used for prolonged periods, the respiratory function must be closely monitored, and a heat and moisture exchanger should be used. Also, intracuff pressures should be checked periodically and maintained at 60 cm H2O. Nitrous oxide diffusion tends to cause a rise in intracuff pressure in the LMA™ cuffs made of silicone. This may result in malposition, postoperative sore throat, or other adverse events.

Brain AIJ, Denman W, Goudsouzian N.G., LMA-Classic and LMA-Flexible Instruction Manual, LMA North America, Inc.

Ferson D, Brimacombe JR, Brain AIJ. International Anesthesiology Clinics: The Laryngeal Mask Airway. Lippincott-Raven, Volume 36, Number 2, 1998.

LMA-Fastrach™

There are reports of pharyngeal edema and increased mucosal pressure attributed to the rigidity of the airway tube. Therefore, it is recommended the LMA-Fastrach™ be removed once intubation has been accomplished. If the LMA-Fastrach™ is left in place after intubation, the cuff should be partially deflated (to a pressure of 20-30 cm H2O).

The LMA-Fastrach™ can be used as a stand-alone device for ventilation. There are no clinical data on how long the LMA-Fastrach™ may be left in place, but there are anecdotal reports of leaving the LMA-Fastrach™ in place for up to 4 hours without sequelae. If a clinical decision is made to leave the LMA-Fastrach™ in place, the tube should be stabilized in the neutral position to prevent unnecessary movement.

Brain AIJ, Verghese C., LMA-Fastrach™ Instruction Manual, LMA North America, Inc.

Keller C, Brimacombe J. Pharyngeal mucosal pressures, airway sealing pressures, and fiberoptic position with the intubating versus the standard laryngeal mask airway. Anesthesiology 1000;90:1001-6.

Nakasawa K, Tanaka N, Ishikawa S et al. Using the intubating laryngeal mask airway (LMA-Fastrach) for blind endotracheal intubation in patients undergoing cervical spine operation. Anesth Analg 1999;89:1319-21.

Question:

Hi, Have there been any studies with the use of LMA with and without Nitrous Oxide Anesthesia? If so how many times did the observer have to adjust the cuff pressure?

Nov. 18, 2005 at 10:21, A.

Dr. Doyle replies:

When the laryngeal mask airway (LMA) is used with nitrous oxide, diffusion of nitrous oxide into the air-filled cuff during the case can cause large increases in LMA cuff volume and pressure; this cuff over-inflation may result in distension of the hypopharynx, with occassional recurrent laryngeal nerve injury. Bruce et al. (Journal of Laryngology & Otology, Volume 118, Number 11, November 2004, pp. 899-901) reported a case of a temporary vocal cord palsy following the use of such an LMA where the development of high cuff pressures secondary to nitrous oxide diffusion into the cuff was proposed as the most likely cause. The authors suggested that mandatory intraoperative cuff pressure monitoring might lower the risk of such problems. Dr. Brain, inventer of the LMA, points out that published inflation volumes represent maximum volumes and recommends not inflating the LMA cuff above a pressure of 60 cm H2O so as to diminish the possibility of compressing nerves or vascular structures. (Brain AIJ. Pressure in laryngeal mask airway cuffs (Letter). Anaesthesia 1996; 51: 603. )

Question:

Also about using LMA in the field(paramedics),we all know that it is not a perfect seal and there is always a chance of complication especialy in agitated patients.Do you use intubating LMA's where after initial stabilization patient gets an ETT with good seal?

Nov. 18, 2005 at 10:21, A.


Dr. Doyle replies:

The role of using the LMA in prehospital medicine remains somewhat controversial in that very many of these patients have "full stomachs" and because endotracheal intubation is the "gold standard" of airway management in the severely injured patient. The intubating LMA certainly could be used in the prehospital setting to provide eventual definitive airway control after LMA insertion following initial ventilation via the intubating LMA, although many clinicians might view such a two-stage process as too complicated and might feel more comfortable with direct intubation in such cases.

Question:

I have two questions... The first: I want to know about your experience in using LMA in prone position.

Nov. 17, 2005 at 17:26, A.


Dr. Doyle replies:

Use of the LMA in prone position remains controversial. It certainly has been done a number of times and a number of case reports on the matter have been published. But most clinicians are concerned that the airway is not secure enough when an LMA is used in a prone patient. On the other hand, the LMA can be very valuable as a rescue technique, as illustrated in the following story:

"A 5-yr-old girl with Arnold-Chiari Malformation, Type 1, was accidentally tracheally extubated while positioned prone in a Mayfield neurosurgical headrest during a decompressive craniectomy and cervical laminectomy. While preparations were being made to return the patient to the supine position for reintubation, we placed a laryngeal mask airway (LMA) without difficulty. The child was kept in the prone position with the LMA in place using positive-pressure ventilation for the remainder of the operation. This case report emphasizes the practical, emergent use of a LMA to secure the airway of a pediatric patient in the prone position after accidental extubation" [R. Scott Dingeman, MD, Liliana C. Goumnerova, MD, and Susan M. Goobie, MD, FRCPC. The Use of a Laryngeal Mask Airway for Emergent Airway Management in a Prone Child. Anesth Analg 2005;100:670-671 ]

Question:

The second question: Is it safe to use LMA in Adenotonssilectomy? Thank you.

Nov. 17, 2005 at 17:26, A.

Dr. Doyle replies:

There have been a number of studies showing that the LMA can be used for tonsillectomy surgery [For example: Williams PJ, Bailey PM. Comparison of the reinforced laryngeal mask airway and tracheal intubation for adenotonsillectomy. Br J Anaesth 1993; 70: 30-3]. Nevertheless, the technique is not popular among otolaryngologists. Here is one opinion from the ENT literature:

"The laryngeal mask airway presents certain advantages in the management of the airway during general anaesthesia. However, from the surgeon's perspective, there have been reports of problems occurring when the laryngeal mask airway is used in tonsillectomy. This study of 90 patients undergoing tonsillectomy suggests that surgical access is inferior with a laryngeal mask airway and the weight of tonsillar tissue excised is less. In addition the laryngeal mask airway needs to be changed to an endotracheal tube during the procedure in 11.4% of patients." [Hern JD, Jayaraj SM, Sidhu VS, Almeyda JS, O'Neill G, Tolley NS. The laryngeal mask airway in tonsillectomy: the surgeon's perspective. Clin Otolaryngol Allied Sci. 1999 Apr;24(2):122-5.]

Question:

I'm curious to know if anyone routinely uses the ProSeal rather than the standard LMA. Our center seems to have stopped stocking them due to cost considerations.

Nov. 10, 2005 at 13:02, H.F.

Dr. Doyle replies:

It would require a formal survey to scientifically answer this question, but my unscientific answer is that it is likely that the ProSeal is more commonly used in Europe than in Canada and the USA, especially for cases involving neuromuscular blockade and positive pressure ventilation.

The LMA-ProSeal (r) laryngeal mask airway has a modified cuff and esophageal drainage tube that not only makes it potentially suitable for use with positive pressure ventilation (PPV), but may also (at least theoretically) lessen the risk of aspiration. This reusable airway has a cuff that is made of a softer material than the original LMA and is designed to conform to the contours of the hypopharynx. While the LMA ProSeal(tm) may be used with spontaneously breathing patients, it is designed for use with PPV, with and without muscle relaxants. The maximum airway seal pressure will vary between patients, but is on average 10 cm H2O higher than the original LMA or up to 30 cm H2O.

The LMA-ProSeal provides better seal than the LMA and facilitates gastric tube placement, but it can be more difficult to insert unless a special introducer tool is used. When correctly positioned, it isolates the glottis from the upper esophagus. The esophageal drainage tube serves primarily as a passive drainage channel and as an indicator of correct mask placement, but allows for the passage of a gastric tube. If used, it may be inserted, the stomach drained, and the tube removed. Alternatively, it may be left in for the duration of the case on low suction or open to the atmosphere. It should be noted that leaving a gastric tube in place decreases the lumen size of the drain tube for its primary function of facilitating drainage.

In Europe and elsewhere, the LMA-ProSeal is not infrequently used for laparoscopic cholecystectomy surgery and other laparoscopic procedures. However, "standard of care" issues may preclude its widespread adoption for this setting in the USA and Canada at this time.

Question:

I know that LMA use has complications associated with its use (pharngeal injury, lingual nerve injury etc). It would be good to include this information relative to OETT complications. I am also interested in knowing if there is a recommendation now to lower volumes put in these cuffs. My recollection is that there is a change in recommended volumes and I know that many folks in my hospital use lower volumes clinically.

Nov. 10, 2005 at 12:17, P.A.

Dr. Doyle replies:

A good place to begin to answer this question is to start with a quote from Spielman [1]: "Complications are infrequent during use of the LMA in the operating room. The most common problems encountered include inability to position the LMA correctly, coughing and gagging during placement and removal, laryngospasm, and postoperative sore throat. Mechanical problems are rare. Brimacombe's [2] analysis of 1500 LMA uses revealed that on two occasions (0.13%) the LMA cuff slowly deflated during the operation secondary to a small leak. Verghese and Brimacombe [3] found that only 44 critical incidents were documented as related to the use of a LMA in 11,910 anesthetics (0.37%), and only 18 (0.15%) of these were related to the airway. None of the incidents concerned structural issues associated with the LMA."

To this I would also note that air leakage and gastric inflation are two very well recognized potential complications of positive pressure ventilation with the laryngeal mask airway [4, 5].

A case of negative pressure pulmonary edema after a patient bit down on a laryngeal mask airway has been reported from the Journal of the College of Physicians and Surgeons of Pakistin [6]. An interesting report in 2004 described a case in which the use of a laryngeal mask airway during an out of hospital cardiac arrest "led to massive gastric dilation, gastric rupture, and a tension pneumoperitoneum"[7].

The issue of optimal LMA cuff pressure has been a matter of some discussion in the literature. I would remind readers that the cuff inflation volumes usually given are maximum values; usually half the maximum value will suffice to get a good seal, corresponding to a cuff pressure around 60 mmHg. Burgard et al. [8] looked at the effect of laryngeal mask cuff pressure on the incidence of postoperative sore throat. The authors noted that the incidence of this problem can be significantly reduced when cuff pressures are continuously monitored and reduced to the minimal pressure required for air tightness by periodically removing gas as nitrous oxide enters the LMA cuff.

Finally, it also goes without saying that if the incorrect size of LMA is used, high cuff pressures may be needed, with resulting complications. Here are the current size recommendations from the LMA Company:

Size 1 Neonates/infants up to 5 kg
Size 1.5 Infants between 5-10 kg
Size 2 Infants/children between 10-20kg
Size 2.5 Children between 20-30kg
Size 3 Children between 30-50kg
Size 4 Adults between 50-70kg
Size 5 Adults between 70-100kg
Size 6 Adults over 100kg


TABLE: Current sizing recommendations for the LMA classic
SOURCE:
http://www.lmaco.com/faqs.php#faq03

References:

[1] Spielman FJ. Complete separation of the tube from the mask during removal of a disposable laryngeal mask airway. Can J Anaesth. 2002;49:990-2.

[2] Brimacombe J. Analysis of 1500 laryngeal mask uses by one anaesthetist in adults undergoing routine anaesthesia. Anaesthesia 1996;51:76-80.

[3] Verghese C, Brimacombe JR. Survey of laryngeal mask airway usage in 11,910 patients: safety and efficacy for conventional and nonconventional usage. Anesth Analg 1996;82:129-33.

[4] Weiler N, Latorre F, Eberle B, Goedecke R, Heinrichs W. Respiratory mechanics, gastric insufflation pressure, and air leakage of the laryngeal mask airway. Anesth analg 1997;84:1025-8.

[5] Ho-Tai LM, Devitt JH, Noel AG, O'Donnell MP. Gas leak and gastric insufflation during controlled ventilation: facemask versus laryngeal mask airway. Can J Anaesth 1998;45:206-11.

[6] Journal of the College of Physicians and Surgeons Pakistan, September 2004.

[7] Haslam N, Campbell GC, Duggan JE. Gastric rupture associated with use of the laryngeal mask airway during cardiopulmonary resuscitation. BMJ 2004;329:1225-6.

[8] Burgard G. Mollhoff T, Prein T. The effect of laryngeal mask cuff pressure on postoperative sore throat incidence. Journal of Clinical Anesthesia 1996;198-201.


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