Aintree

THE AINTREEINTUBATION CATHETER

1. Insert the Laryngeal MaskAirwayMeanwhile load the Aintree IntubationCatheter over the fibreoptic intubatingbronchoscope

2. Pass the bronchoscopewith the Aintree IntubationCatheter through theLaryngeal Mask Airwayinto the trachea

3. Remove the fibreopticintubating bronchoscopeleaving the AintreeIntubation Catheter in thetrachea

4. Remove the LaryngealMask Airway then load theendotracheal tube ontothe Aintree IntubationCatheter

5. Railroad the endotrachealtube over the AintreeIntubation Catheter andpass into the trachea

6. Remove the AintreeIntubation Catheter,leaving the endotrachealtube in the tracheaThe fibreoptic bronchoscope can then beused to confirm correct endotracheal tubeplacement in the trachea

Dr. Michael LimDr. Julian Hunt-Smith

Intensive Care CentreSt. Vincent�s HospitalMelbourneVictoria 3065Australia

IntroductionIn the event of an unexpected difficultlaryngoscopy the Laryngeal MaskAirway (LMA) has been advocated bymany prominent authorities as a conduitfor the fibreoptic laryngoscope1. In ananaesthetised patient, this approach offersadvantages over attempting either a blindintubation via a LMA or a fibreoptic-assisted endotracheal intubation.However, even this approach hasdrawbacks, which are eliminated throughthe use of the Aintree Intubation Catheter.

Problems with BlindIntubation Through theLaryngeal Mask AirwayThe ease of correctly positioning a LMAis independent of the difficulty oflaryngoscopy. This confers a significantadvantage in the difficult airwaysituation. The logical next step wouldthen seem to be to insert a gum-elasticbougie through the LMA, as its apertureshould be directly over the glottis if theLMA is positioned correctly. However,even if the LMA is providing a clinicallyacceptable airway, it may not be in ananatomically correct position. Hence theblind passage of a bougie through theLMA may be unsuccessful. Furthermore,it is as likely that the bougie may passthrough one of the lateral slits as it wouldpass between the two central slits. Clearly,if it passes through one of the lateral slits,it will deviate away from the laryngealoutlet. In one study, the success rate withthis technique was only 28%2. First-timeinsertion rates via the Intubating LMAhave been found to be 80%

3.

In addition, the blind passage of a bougiehas the potential for trauma to the upperairway in a similar way to the injuriescaused by repeated attempts atlaryngoscopy.

Problems with Fibre-optic Endotracheal

Intubation in anAnaesthetised Patient

Whilst awake fibreoptic laryngoscopy isgenerally considered to be the goldstandard for difficult intubations, byproviding a high success rate with a lowlevel of complications, once the patientis anaesthetised and so loses tone in theupper airway, it becomes considerablymore difficult. This loss of upper airwaytone will result in the walls of the upperairway opposing each other, preventinga clear passage for the fibreopticlaryngoscope and obscuring its view.

Problems with Fibre-optic Endotracheal

Intubation through theLaryngeal Mask AirwayFibreoptic assisted endotrachealintubation through the LMA overcomesthe problems mentioned above byproviding an airway for the fibreopticlaryngoscope, whilst the fibreopticlaryngoscope can act as a �directablebougie� once it exits the LMA. Indeed,this technique has a success rate as highas for awake fibre-optic intubation.However, this technique also has itspitfalls4:

• The cuff of the endotracheal tubemight be above or over the vocalcords.A standard endotracheal tube willonly protrude for 8cm beyond thegrille of the LMA. If the distancefrom the grille to the vocal cords isthen more than 3cm, theendotracheal tube cuff will besituated over the vocal cords. Thiscould result in an incomplete sealand damage to the vocal cords

• The smaller endotracheal tube maynot allow adequate ventilation.A Size 4 LMA will accept a 6.5mminternal diameter endotracheal tube,whilst a Size 5 LMA will accept a7mm endotracheal tube. Whenconsidering the appropriate bodyweights for which these LMAs, thenit may be difficult to achieve anadequate minute volume withoutunacceptably high airway pressures.

• Risk of extubation if removing theLMA

The Aintree IntubationCatheter

This is an adaptation of the Cook AirwayExchange Catheter® with a largerinternal diameter (4.8mm) to allow it tobe pre-loaded onto a 4.0mm fibreopticlaryngoscope5. Its external diameter(6.5mm) allows its use with endotrachealtubes whose inner diameter is 7mm orlarger. It is 56cm long so that once loadedonto the fibre-optic laryngoscope, thedirectable distal 3cm of the laryngoscopeis left free. The catheter also hasremovable Rapi-Fit connectors, whichallows the use of a ventilatory device ifnecessary during the exchange procedure.As can be seen from the figures on theright, it allows full control of the airwaythroughout the intubation procedure.Clearly, a larger endotracheal tube can beinserted without being impeded by theLMA. The risk of accidental extubationif the LMA is removed is also eliminatedas the LMA is removed before theendotracheal tube is actually inserted.

In summary, the Aintree IntubationCatheter offers an elegant solution to theproblems associated with fibreoptic-guided endotracheal intubation using alaryngeal mask airway as a conduit.

For Fibreoptic Assisted Endotracheal Intubation via the Laryngeal Mask Airway

INSERTION TECHNIQUE

References1. Benumof JL. Laryngeal mask airway and the

ASA difficult airway algorithm.Anesthesiology 1996; 84(3): 686-99.

2. Gabbott DA, Sasada MP. Trachealintubation through the laryngeal mask usinga gum elastic bougie in the presence ofcricoid pressure and manual in linestabilisation of the neck. Anaesthesia 1996;51(4): 389-90.

3. Baskett PJF, Parr MJA and Nolan JP. Theintubating laryngeal mask. Results of amulticentre trial with experience of 500cases. Anaesthesia 1998; 53(12): 1174-1179

4. Asai T, Latto IP, Vaughan RS. The distancebetween the grille of the laryngeal maskairway and the vocal cords. Is conventionalintubation through the laryngeal mask safe?Anaesthesia 1993; 48(8): 667-9.

5. Atherton DPL, O�Sullivan E, Lowe D,Charters P. A ventilation-exchange bougiefor fibreoptic intubations with the laryngealmask airway. Anaesthesia 1996; 51: 1123-1126.

AcknowledgementsDr DY Williams and the ICU nursing staff, St.

Vincent�s Private Hospital, Melbourne.

These recommendations are intended to serve as a general guideline only. Please refer to the manufacturer�s instructions prior to use