Anesth Analg 2007; 105:1509-
© 2007 International Anesthesia Research Society
doi: 10.1213/01.ane.0000282774.15480.85
LETTER TO THE EDITOR
The Conventional LMA®: Benchmark for Assessing Supralaryngeal Airway Efficacy?
Markus Lange, MD,
Norbert Roewer, MD, PhD, and
Franz Kehl, MD, PhD, DEAA
Department of Anaesthesia and Critical Care; University of Würzburg; Würzburg, Germany; franz.kehl{at}mail.uni-wuerzburg.de
In Response:
The results of our study indicate a higher rate of gastric insufflation in the streamlined liner of the pharynx airway (SLIPA) group. Miller and Vamadevan (1,2) conjecture that this was produced by using inappropriately sized SLIPA's and the limited experience of investigators with the handling of SLIPA's. However, the anesthesiologists participating in our study had at least 3 yr of experience with supraglottic airway devices and were given the opportunity to introduce at least 20 SLIPA devices before the start of the study. Furthermore, the failure rate in our study was only 2% in the SLIPA group, and there was no difference in ease of insertion between the SLIPA and the laryngeal mask airway (LMA). In the SLIPA group, in 21 patients the largest available Sizes 55 and 57 were introduced. In contrast, only one patient received a conventional LMA Size 6, whereas 26 patients received LMA Size 5. Moreover, gastric insufflation in the SLIPA group (19%, n = 11) occurred equally often using Sizes 51 (n = 3), 53 (n = 3), 55 (n = 3), and largest Size 57 (n = 2) and no gastric insufflation was observed when the smallest Sizes 47 and 49 were used. Thus, we refute the notion that too small a size of the SLIPA was used that might have led to gastric insufflation. In Dr. Miller's study, a version of the SLIPA was used (4) that differed in design from the one used in our study. Whether this difference, be it marked or minor, transfers into a disparity in clinical performance or patient comfort, can only be decided by a direct comparison in a controlled patient study that to our knowledge has not been performed yet.
Dr. Vamadevan (2) disagrees with our statement that higher sealing pressures theoretically might provide superior protection against pulmonary aspiration and Dr. Miller (1) criticizes our conclusion that patients in the SLIPA group may have been at higher risk for aspiration. Positive pressure ventilation is routinely used with supraglottic airway devices. If the inspiratory peak pressure exceeds the sealing pressure of the airway device, gas insufflates the stomach and might increase the risk of regurgitation. However, as discussed in our publication, no regurgitation of gastric contents was observed in any group in this clinical investigation and theoretically the fluid collection chamber of the SLIPA might prevent aspiration. In a laboratory study by Dr. Miller, it was demonstrated that the SLIPA effectively reduced aspiration after regurgitation compared to the Classic LMA (4). However, these experiments were performed using a phantom model, specifically designed for the study. Thus, a direct transfer into clinical practice is not possible. Because of the specific conditions of surgery and anesthesia during which patients are passively positioned, buck, or cough during awakening, it is unclear whether regurgitated gastric volume will effectively be captured in the hollow chamber of the SLIPA. As long as it has not been proven in a clinical study with a large patient population that the risk of pulmonary aspiration with the SLIPA is comparable to that of other supraglottic airway devices with inflatable cuffs, it is fair to conclude that the greater rate of gastric air insufflation with the SLIPA might put patients at increased risk for regurgitation or aspiration.
REFERENCES
- Miller D. Laryngeal Mark airway classic and streamlined pharynx airway linear airway comparison. Anesth Analg 2007;105:1508[Free Full Text]
- Vamadevan S. The conventional LMA® benchmark for assessing supra laryngeal airway efficacy?. Anesth Analg 2007;105: 1508–9[Free Full Text]
- Lange M, Smul T, Zimmermann P, Kohlenberger R, Roewer N, Kehl F. Effectiveness and patient comfort of the novel streamlined pharynx airway liner (SLIPA) compared with the conventional laryngeal mask airway in opthalmic surgery. Anesth Analg 2007;104:431–4[Abstract/Free Full Text]
- Miller DM, Light D. Laboratory and clinical comparisons of the streamlined liner of the pharynx airway (SLIPA) with the laryngeal mask airway. Anaesthesia 2003; 58:136–42[Web of Science][Medline]
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