LMAs in Children

Most pediatric patients do not need an endotracheal tube (ETT) for procedures requiring general anesthesia

By Valerie E. Armstead, MD, FAAP
Attending Anesthesiologist, St. Joseph’s Regional Medical Center & Children’s Hospital, Paterson, NJ
Affiliate: Department of Anesthesiology,
Mount Sinai School of Medicine, New York, NY

Endotracheal intubation is the OLD standard for securing the airway in adults and children. Almost 50% airways are now managed with a supraglottic airway (SGA) for general anesthesia(2). Thanks to SGAs there are more stable hemodynamics on induction and emergence. The modern maxim is when in doubt, intubation may not be the best choice for the patient.

The supraglottic airway (SGA), which is most notably represented by iterations of the laryngeal mask airway (LMA) introduced by Dr. Archie Brain, has become a very powerful airway management device. However, I am compelled to invoke the often-quoted Spider-Man theme of “with great power comes great responsibility”(1). I recall having to spend two afternoons with Dr. Rich Epstein, first observing and then being observed in the use of the LMA in pediatric patients. I was also required to watch the teaching video of Dr. Brain’s (Left-handed) LMA insertion technique as well as pass a written test before being granted LMA privileges at Thomas Jefferson University Hospital in 1992. I also received an official document of this accomplishment signed by the Hospital CEO. Based on what was proper SGA training, I believe the lack of responsibility in the use, and worse, improper teaching of the use of LMAs and other SGAs has resulted in complications that are preventable.

The major points in this discussion will delineate the circumstances whereby SGAs should be used instead of the endotracheal tube (ETT) as well as the indications and contraindications for SGAs. As a former member of the US FDA committee (ASTM international, F29.12) that established the standards for SGAs after the patent on the LMA expired, it is also my responsibility to extol the virtues of some of the 19 and counting SGAs that are in use for anesthetic care.

Although there are now a myriad of SGAs that can be used for routine general anesthetics in children, the LMA airways are the most studied and widely used(2). LMA of North America states the following on their website(3):

Indications
LMA airways are indicated for use as an alternative to the face mask for achieving and maintaining control of the airway. LMA airways are not indicated as a replacement for the endotracheal tube. LMA airways are indicated for use in:

• Routine and emergency anesthetic procedures
• Known or unexpected difficult airways
• Establishing an airway during resuscitation in the profoundly unconscious patient with absent glossopharyngeal and laryngeal reflexes when tracheal intubation is not possible

Contraindications
As a routine airway, LMA airways are contraindicated in elective patients who:

• Have not fasted or where fasting cannot be confirmed
• May have retained gastric contents
• Have fixed decreased pulmonary compliance

As a rescue airway, LMA airways are contraindicated in patients who are not profoundly unconscious and who may resist LMA airway insertion. Clinical judgment must be used to weigh the risk of regurgitation and aspiration against the potential benefit of establishing an airway.

Anyone who is familiar with the extensive use of the LMA airways outside of the US is aware that the position of the patient is not use-prohibitive; even the prone position. In fact, SGAs have been used to rapidly establish airway control during extubation of prone, anesthetized patients or in trauma situations where it is difficult to access the victims.

The notion of “when in doubt-intubate” may not be the safest alternative based on evidence comparing the LMA to ETT in general anesthesia. A systematic review of 29 randomized prospective controlled trials compared the risk of airway complications with an LMA versus an endotracheal tube (ETT) in patients receiving general anesthesia. For the patients receiving general anesthesia, the use of the LMA resulted in a statistically and clinically significant lower incidence of laryngospasm during emergence, postoperative hoarse voice, and coughing compared to ETT use(2). The risk of aspiration could not be determined because only one study reported a single case of aspiration, which was in the group using the ETT. Furthermore, the dreaded manifestations of airway irritability such as major oxygen desaturation, bronchospasm, and overall adverse events compared to the LMA with intercurrent upper respiratory (URI) can be averted with use of LMA instead of the invasive, irritating ETT according to studies conducted by Tait, Malviya, et al(4). Moreover, multiple, robust-sized, prospective studies have shown that tracheal intubation in children with URIs increases the risk of respiratory complications by 11-fold and ETT use is an independent risk factor for adverse respiratory events in children with URIs(4-6). The take away message from these & other studies should be “When in doubt-Do not intubate” for the child with URI having procedures where SGAs are an option for airway management.

Another myth that is gradually being dispelled through well-designed studies is the use of positive pressure mechanical ventilation with SGAs is prohibited during anesthesia. The standards for SGA design require the ability to provide positive pressure. Proper insertion technique and appropriate ventilation settings can provide for safe, effective ventilation for a variety of conditions and procedure durations(7). In fact, the SGAs with isolated channels for gastric decompression such as the ProSeal™ Laryngeal Mask Airway (PLMA) for children were introduced in 2004, by Dr. Archie Brain and later iterations such as the LMA Supreme™. These latest versions were designed specifically to allow positive pressure, mechanical ventilation (PPV). In a prospective, randomized study comparing ETT to PLMA investigators found that insertion of PLMA as well as ETT was performed in the first attempt in all the patients(8). Ease of insertion and conditions during insertion were comparable in both the groups. Changes in SpO2 and EtCO2 were comparable. In addition, gastric insufflation, regurgitation, pulmonary aspiration, postoperative airway complications were no different in with the PLMA or ETT. However, highly significant changes in hemodynamic parameters were observed in the ETT group. Thankfully, modern anesthesia machine ventilators also allow for complementary modes of PPV, such as pressure support when using SGAs. Therefore, the notion that children would or should be relegated to spontaneous ventilation during SGA use is not in keeping with current technology. Finally, the latest revision to “Standards for Basic Anesthetic Monitoring” by the American Society of Anesthesiologists (ASA) effective July 1, 2011 requires the use of end-tidal CO2 (etCO2) monitoring(9). This salutary addition to monitoring standards obviates any arguments regarding whatever airway or circuit system is being used. True, the etCO2 during SGA may not reflect the true etCO2; however, the same situation occurs with a cuffless or leaking ETT.

In the spirit of using scientific evidence to address legitimate versus anecdotal or theoretical problems a few more issues will be discussed.

Airway protection may actually be superior with the LMA as demonstrated by anesthesiologists who compared ETT to flexible shaft/armored LMAs in sinus surgery in pediatric patients. In this study there was significant contamination of the subglottic region with the ETT and none in the LMA group. This group concluded that the LMA exhibited a better protection of the airway than an uncuffed ETT with throat pack. The investigators theorized that the LMA covers the supraglottic and glottic airway, so blood is diverted laterally to the piriform sinuses and postcricoid regions. This effectively protects the glottic airway from these fluids, which can then be suctioned orally at the conclusion of surgery and before emergence. In contrast, the external surface of the ETT can act as a conduit for blood from the oropharynx to the larynx and tracheobronchial tree, probably by means of capillary action of the throat pack around the ETT. These investigators found the LMA a superior airway management choice. The ETT was problematic on multiple levels due to the combination of blood/secretion exposure (either visible or nonvisible). The direct stimulation of the tracheal lumen by the ETT, and the use of the throat pack might explain the prolonged recovery time and greater incidence of cough among patients in the ETT group(10).

There is also the concept of prevention of airway complications and improvement in patient satisfaction with LMA management. Drs. David Wong, Frances Chung and others at University of Toronto first presented this award-winning research at the Society for Airway Management annual meeting in 2009. In their very elegant, low tech, high concept study, an observer used a hand-held manometer to measure LMA cuff pressures in over 200 adult patients undergoing general LMA anesthesia. Patients were randomized to pressure limiting (release of intracuff pressures to less than 44 torr) or routine care (No intervention; even if intracuff pressures were in the 100s)(11). This monitoring was repeated on the hour as needed. This simple intervention resulted in statistically significant decreases sore throat and other airway complications. This simple intervention resulted in relative risk reduction of 70.6%, absolute risk reduction of 32.3%, and number needed to treat three. Because of this research, I and other anesthesiologists carry hand-held manometers that display appropriate pressure ranges for LMAs as well as for ETT cuffs. These studies by Wong and Chung raise questions about the past and ongoing complications of SGAs. Several airway product manufacturers sell manometers for around $100. This is a reasonable investment when preventing complications.

A number of the SGAs are reusable. The environmental impact of one less plastic ETT or SGA in hospital trash is very positive.

The nuances of SGA use, when conducted in a responsible manner, can further reduce or prevent complications from routine general anesthesia. It is time to stop clinging unnecessarily to the ETT. I encourage those still unfamiliar with the SGA family to attend workshops or perform due diligence before test driving.

Finally, I encourage you to join the Society for Airway Management (SAM) and attend their annual meetings. There you can learn a wide variety of airway management skills while often being taught by the inventor or someone happy to transfer their knowledge to you.

References:

1. Lee S, Ditko D, Amazing Fantasy #15, August 1962
2. Yu SH, Beirne OR., Laryngeal mask airways have a lower risk of airway complications compared with endotracheal intubation: a systematic review. J Oral Maxillofac Surg. 2010 Oct;68(10):2359-76.
3. www.lmana.com
4. Tait AR, Malviya S, Voepel-Lewis T et al. Risk factors for perioperative adverse
   respiratory events in children with upper respiratory tract infections. Anesthesiology
   2001;95:299-306.
5. Cohen MM, Cameron CB. Should you cancel the operation when a child has an upper respiratory tract infection? Anesth Analg 1991;72:282-8.
6. Parnis SJ, Barker DS, Van Der Walt JH. Clinical predictors of anaesthetic complications in children with respiratory tract infections. Paediatr Anaesth 2001;11:29-40.
7. Jamil S, Mehtab Alam, Usmani H, Khan M M ,Indian J Anaesthesia 2009; 53 (2):174-178
8. Patel MG, Swadia V, Bansal G. Prospective randomized comparative study of use of PLMA and ET tube for airway management in children under general anaesthesia. Indian J Anaesth. 2010 Mar;54(2):109-15.
9. http://www.asahq.org/For-Members/Clinical-Information/Standards-Guidelines-and-Statements.aspx: Standards for Basic Monitoring
10. Webster AC, Morley-Forster PK, Janzen V, Watson J, Dain SL, Taves D, Dantzer D. Anesthesia for intranasal surgery: a comparison between tracheal intubation and the flexible reinforced laryngeal mask airway. Anesth Analg. 1999 Feb;88(2):421-5.
11. Seet E, Yousaf F, Gupta S, Subramanyam R, Wong DT, Chung F.Use of manometry for laryngeal mask airway reduces postoperative pharyngolaryngeal adverse events: a prospective, randomized trial.Anesthesiology. 2010 Mar;112(3):652-7.