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Department of Anesthesiology, Baystate Medical Center, Tufts University Medical School, Springfield, MA
To the Editor:
We read with interest the report by Rosenblatt (1) where a LMA ProSeal TM was used to resuscitate a patient who had an unanticipated difficult intubation with subsequent difficult ventilation caused by gastric insufflation. While we congratulate the author for his successful rescue of this patient, we disagree with the premise that the LMA ProSeal should be advocated as a primary solution to this dilemma. While it is well accepted that the placement of the LMA Classic TM and LMA Fastrach TM are easily accomplished, this is not the case with the LMA ProSeal. Even experts in the use of the LMA ProSeal report first attempt success rates for placement of only 77–90% (2–5). These rates of successful first placement are consistently less frequent than with the Classic LMA (4). Attempted ventilation after improper placement of the LMA ProSeal can by itself increase the risk for aspiration of gastric contents (7). The problem with the patient in this case was that the combination of four attempts at direct laryngoscopy with tonsillar hyperplasia made it difficult to obtain a view with the fiberoptic bronchoscope. The direct laryngoscopic view was grade III; thus the next logical choice should have been a rigid fiberoptic intubating scope such as the Bullard or the Wu scope. Rigid fiberoptic intubating scopes are often ideal for this situation (hypertrophied tonsillar tissue) in that they retract the swollen tissue and epiglottis out of the way and create their own lumen through which the glottis can be visualized. This allows rapid intubation of the trachea. The triad of the fiberoptic bronchoscope, the LMA Fastrach, and a rigid fiberoptic scope should be the foundation of the approach to the difficult airway. When one method fails, the other two techniques provide back up. The LMA ProSeal, as illustrated by this case, is a valuable tool in experienced hands. However, for the general population of anesthesia care providers who have not had extensive experience using the LMA ProSeal, it should not be considered the method of choice for the difficult to intubate/ventilate scenario.
References
Professor of Anesthesiology and Surgery, Yale University School of Medicine, New Haven, CT
In Response:
Thank you for allowing me to respond to the letter by Dunn et al. regarding my report (1).
First, I believe that the correspondents misinterpreted my remarks. Nowhere in the report do I advocate turning to the ProSeal TM Laryngeal Mask Airway (PLMA) as a "primary solution." In the case reported, the PLMA was the fourth device used after failed direct laryngoscopy. A unique facility of this particular supraglottic airway resulted in the restoration of oxygenation.
This patient was managed in accordance with the recent republication of the American Society of Anesthesiologist’s Difficult Airway Algorithm (ASA-DAA) (2): failure to intubate by direct laryngoscopy was followed by face mask ventilation. Initially, when face mask ventilation was adequate, "alternative approaches to intubation were employed." (2) When oxygenation by face mask ventilation became inadequate, a laryngeal mask device was inserted, and adequate oxygenation was restored through gastric decompression, a unique facility of the PLMA. According to the ASA-DAA it would have been inappropriate, when oxygenation was failing, to turn to another "alternative" device, such as a rigid laryngoscope.
The correspondents express concern that first attempt success rates with the PLMA are low (77–90%). In all but one of the studies cited in their letter, the criteria for a "successful" placement was strict (e.g., a designated tidal volume, no air-leak) and do not imply that oxygenation and ventilation were inadequate. Oddly, first and multiple attempt success rates with a Bullard laryngoscope were equally as low in untraumatized airways in a study authored by one of the correspondents (77% and 91%, respectively) (3). In addition, in every study cited, the second or third PLMA placement resulted in success rates higher than that achieved with the Bullard scope (3). Laryngeal mask airways have become a staple in the operating room and the clinician has ample opportunity to become expert with their use (4). Rigid fiberoptic devices have not enjoyed wide dissemination (4). For those who find difficulty with PLMA insertion, alternative methods have been described (5).
The correspondents state that the "foundation of the approach to the difficult airway" should be the triad of the flexible bronchoscope, Fastrach LMA, and rigid fiberscope. These authors offer no support for their assertion. This blanket statement fails to assess the cause of the difficulty and does not account for the trauma of initial direct laryngoscopy, which can obscure the use of any indirect-vision technique (6). This simplified approach ignores all of the considerations of the ASA Difficult Airway Task Force (2). The approach suggested by these authors implies that tracheal intubation is a requirement for airway resuscitation. The patient described in my report did not require tracheal intubation – she needed oxygenation. These should not be confused. Tracheal intubation with a rigid fiberoptic laryngoscope would have required more time (3) and would not have improved the patient’s condition until gastric decompression had been accomplished. There is evidence that preoccupation with tracheal intubation results in greater morbidity when ventilation and oxygenation can be achieved by less invasive means (7).
Last, the correspondents discuss that ventilation after improper placement of the PLMA can increase the risk of gastric content aspiration. This is true of any laryngeal mask (8). Importantly, the LMA ProSeal is the only currently available supraglottic airway that allows the operator to assess its proper position (8,9).
All of the resuscitative devices described in these discussions are capable. The clinician must consider the advantages of each and become proficient in their use before their application in an emergency. The PLMA simply offers another resuscitative possibility. In airway resuscitation, flexibility and not rigidity leads to success!
References
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