[Distance from the laryngeal mask grip to endotracheal tube tip. A crucial point during fiberoptic intubation in children]

J Mauch, T Haas, M Weiss
Der Anaesthesist 2012, 61 (2): 123-8

BACKGROUND: Management of difficult airways and difficult intubation differs in pediatric and in adult patients. In conscious children, fiberoptic intubation is not feasible because of limited compliance. The specially designed laryngeal mask for blind tracheal intubation, LMA Fastrach™, is available for adolescents and adults only. Therefore, fiberoptic-guided intubation through a supraglottic airway device (SAD) is a standard technique for the management of difficult intubation in children. While performing the procedure, stabile positioning of the endotracheal tube (ETT) and prevention of dislodgement are critical issues. The relationship between the length of the ETT and the SAD is highly important and was investigated in this in vitro study.

MATERIALS AND METHODS: In this study 6 different brands of SAD in the pediatric sizes 1-3 and 2 different ETT brands (cuffed, Microcuff(®), uncuffed, Sheridan PED-SOFT™) were investigated. Using pediatric growth tables, the recommended patient weight for each SAD size was correlated to patient age and then to appropriately sized cuffed and uncuffed ETTs. The ETT size was chosen according to the manufacturer's recommendations (cuffed ETT) and according to the literature (uncuffed ETT). The various SAD-ETT pairs were assessed with regard to differences in their length. After lubrication with silicone the ETT with a firmly attached 15 mm tube adapter was maximally inserted into the SAD and the ETT tip overlapping the SAD cuff was measured. Secondarily, an adapter for fiberoptic procedures was interposed and the measurements repeated.

RESULTS: For a defined patient uncuffed ETTs were usually selected with a larger internal diameter (ID) compared to cuffed ETTs. Therefore, the uncuffed ETT is the longer one and will overlap the SAD by a longer tip. Comparing the curved SAD brands AuraOnce™ and Aura-i™, the Aura-i™ devices generally showed shorter tubes resulting in a longer protruding ETT tip (median 1.5 cm, minimum-maximum 1.0-2.4 cm). The straight brands LMA classic™, AuraStraight™ and LMA Unique™ showed similarity in tube length. In comparison with i-gel(®), for the SAD sizes 1-2.5 the former provide a longer projecting ETT tip. Only i-gel(®) together with AuraStraight™ showed the longest overlapping ETT tip for SAD size 3. If a swivel adapter was used during the fiberoptic intubation procedure, the length of the ETT could be critically reduced in relation to the length of the SAD. Using a swivel adapter from VBM Medizintechnik, (Sulz a. N., Germany) a relative reduction in ETT length of 2.3 or 3.2 cm has to be taken into account.

CONCLUSIONS: For fiberoptic-guided endotracheal intubation through an SAD, sufficient length of the ETT in relation to the SAD is mandatory. Differences in geometry between SAD and ETT brands have to be considered. The selection of a relatively small SAD in combination with an uncuffed ETT might be advantageous. Redesigned extra long ETTs would be desirable to decrease the risk for ETT dislocation and to increase the safety of the technique. Restrictive use of a swivel adapter during the procedure is important because of further and potentially critical decreases in ETT length. In addition, after successful intubation of the trachea, removal of the SAD via an airway exchange catheter and replacement of the cuffed ETT of choice in the correct position is recommended to secure the airway and provide unimpaired ventilation and oxygenation.

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