Friday, March 20, 2015
By Marcelo Sperandio Ramos MD Proper supraglottic airway insertion technique has a steep learning curve, however the success using the device in the management of the airway is the result of an individual expertise with each of the available devices.
Personal experiences by Marcelo Sperandio Ramos MD, Anesthesiologist at cancer center A. C. Camargo and University of São Paulo
I graduated and became an anesthesiologist in the days before the “Laryngeal Mask Airway”, so I witnessed the evolution of both the supraglottic devices themselves and the reaction of the anesthesiology community to these devices.
A supraglottic device is not a sealing device like the endotracheal tube is, but a device that makes spontaneous and positive pressure ventilation possible. Nowadays we live in an era in which ventilation via supraglottic devices is not something new or experimental. These devices make ventilation possible, even in extreme uses, but they are not devices that can reliably dismiss our concerns about ventilation of stiff lungs and possibility of aspiration.
The advent of second/third generation devices with the built in gastric decompression routes (like the LMA Proseal®, LMA Supreme®, air-Q® Blocker, i-gel®, Ambu AuraGain®, etc.) extended the horizons of the devices into an unmapped territory of extreme uses: prone / lateral / "jack knife" patients, video laparoscopies with pneumoperitoneum, and steep Trendelenburg position and so on. Not all anesthesiologists dare to go into this still controversial use.
All the commercial devices can be employed for 4 purposes listed below. The following is a personal preference based on my personal experience, as well as the best advice I could get from literature.
As primary elective airway my first choice is Ambu® Aura (in any of the models). I usually place it without a laryngoscope, just slide it against the hard palate under a deep level of propofol anesthesia.
As a rescue for a failed intubation my choice is for any of the Ambu Aura® family, as well as the air-Q®. In spite of the fact that the LMA Supreme® also perform well in this scenario, I would rather have a device that can help me better in the next step – intubation. When I place an air-Q ® I use some help of the old Macintosh blade to displace the tongue, due to the somewhat bulkier design of the inflatable cuff of this specific device. I usually do not remove the plastic protection of the cuff valve. I place it like it is shown in the video from the manufacturer: https://www.youtube.com/watch?v=E0a1KYwfDk0).
As a device for blind intubation the LMA Fastrach® was the first device devised for this use. It was my first choice until I first used an air-Q® for blind intubation, from this day on air-Q® became my choice for blind intubation.
As a conduit for intubation with an endoscope my choice is the Ambu Aura-i®, followed very closely by the air-Q®. For this task neither of the LMA family performs as well as Ambu Aura-i® or Air-Q®: the LMA Classic® have a long stem that makes it difficult to reach the trachea with the tube; the LMA Fastrach® has the "annoying epiglottis elevating bar", the LMA Supreme® can only be employed with the Aintree Intubation Catheter® two step technique:
Supraglottic devices has evolved: the classic LMA lost its bars which once were devised to avoid the epiglottis to get into the stem of the LMA. As an improvement of the LMA Classic®, the LMA Fastrach appeared as an option to either rescue the airway and/or be a blind conduit for endotracheal intubation. It was sold with a special armored tube, which has a conic tip and a detachable 15 mm connector. The short stem of the LMA Fastrach®, that allowed the intubation proved a good idea, so it was replicated in the newer devices like the Ambu Aura-i® and air-Q®.
The technique of pushing the tip of the LMA against the hard palate and advancing it until a resistance is felt is the standard technique for all the devices. The biggest problem of insertion is that the tip sometimes folds, either to the lingual or to the palatine aspect, resulting in an incorrect position that hinders ventilation. This kind of problem occurred more often with the oldest devices (reusable), the newest incorporate a stiffer palatine aspect and the disposable devices are less pliable and less prone to fold.
In order to avoid this fold, the anesthesiologist usually directs with a finger the introduction of the device. I always grab the jaw with my thumb lying over the internal aspect of the lower incisive and lift the jaw; an equivalent maneuver is to have someone to provide you a "jaw thrust", pushing up the angles of the mandible, as you slide the device against the hard palate.
I have no experience neither with the i-gel® that has a no inflatable cuff nor with the King LT® that has two cuffs.
I also have no experience with the hybrid device TotalTrack VLM® (mannequins only, not in patients), that we could call the "ultimate supraglottic device" because it has all the features of the preceding devices (including the ability to video intubate the trachea, like the LMA CTrach®, that is not manufactured anymore), but need a good mouth opening due to its bulky size.
Marcelo Sperandio Ramos is Anesthesiologist at cancer center A. C. Camargo and University of São Paulo. Dr Ramos is member of Society for Airway Management and gives frequent lecturer about airway management in several scientific meeting in regional societies in Brazil. He is former member of the scientific board of Society of Anesthesiologists of State of São Paulo, and the author of the book: Use of endoscope in airway management.
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For what purposes can a supraglottic device be employed?