I really like the LMA Supreme, which is a next generation LMA, or laryngeal mask airway. Ease of insertion, presence of a gastric port, and the option for using higher ventilatory pressures make the LMA Supreme more versatile and applicable for use in higher risk patients. However, if you’re a fan of using alternative placement techniques for inserting the the Unique LMA, or its reusable version the Classic LMA, it can be a little challenging to use. Also, if you aren’t careful you can give your patient a nasty cut on the lip during insertion. How does the Supreme differ from the Unique?
Challenges With Classic LMA Insertion
The Unique LMA, compared to the LMA Supreme, has a comparatively long, flexible tube attached to the mask. The recommended optimal insertion technique entails:
- deflating and flattening the cuff,
- placing the cuff tip against the hard palate
- sliding the device inward while holding it firmly against the palate until it seats at the upper esophageal sphincter
- inflating the cuff
However, many providers don’t use the recommended technique. Because the Classic LMA is very flexible, there are many alternative insertion techniques in common use. These include, among others,
- inserting it with the cuff fully inflated,
- inserting it straight into the mouth, avoiding the palate completely,
- inserting it upside down and then rotating it into position once in the posterior pharynx.
Some people use these alternative techniques because they think it’s easier than sliding the LMA along the palate — and it usually works reasonably well most, but not all, of the time. The problem is that unless you do slide it along the palate, the LMA may not be well positioned.
- Insertion with the cuff inflated makes incomplete insertion more likely because you can’t insert it as deep. It’s more likely to have a poor seal against the esophageal sphincter making aspiration risk is higher.
- Insertion straight into the mouth increases the risk of folding the mask tip and possibly trapping the epiglottis, risking obstruction or epiglottic swelling.
- Inserting it upside down and then rotating it can leave the LMA partially rotated beyond your line of sight. When malpositioned it’s prone to unexpected obstruction, especially if the head is moved.
Advantages of the LMA Supreme
The LMA Supreme is designed to make optimal insertion technique easier. Compared to the Unique LMA, the tube on the LMA Supreme is shorter and made of hard plastic. It is preformed into the optimal curve to allow even the inexperienced inserter to slide it into position over the glottic opening. The Supreme has a reinforced tip intended to prevent it from folding over and to allow it to easily slip under the arytenoids.
Form Forces Good Insertion Technique
Because of its shape and rigidity, you have no choice but to use the recommended “slide-along-the-palate” technique, making the above mentioned problems less likely. However, those providers who are used to using those alternative “Unique” techniques can no longer use them — and some find that a challenge when first learning how to use the Supreme.
Separate Gastric Suctioning Channel
Another advantage to the LMA Supreme is the presence of a separate channel that lines up with the esophagus. This channel allows suctioning of stomach contents by placement of an oro-gastric tube, allowing:
- both passive and active removal of stomach contents
- decrease of potential aspiration risk by providing an exit for any gastric reflux that might occur
- reduction of gastric distention during ventilation because the esophageal port vents excess gas
It’s important to note that this suction channel must be in line and optimally in contact with the upper esophageal sphincter in order to work well.
Higher Sealing Pressures
Finally, the LMA Supreme is designed to allow higher ventilatory sealing pressures. You can ventilate with inflation pressures up to 37 mmHg without “popping-off”.
When To Use The LMA Supreme vs the Classic LMA
The LMA Supreme is slightly more expensive, certainly a consideration in today’s economy. Most hospitals, including mine, currently restrict its use to those patients for whom it’s a real advantage. Good patient candidates include:
- morbidly obese patients: because of the ability to suction or vent the stomach in these patients who may need higher ventilatory pressures and be at higher risk of reflux
- patients who may need to be cared for in positions other than supine, because the LMA tends to remain more stationary in the oropharynx with movement
- edentulous patients: because the stiff shape stabilizes the LMA, making it less likely to slip out of position in the more lax oral cavity
Remember that just because you can use an LMA doesn’t mean you necessarily should. Remember that patients at high risk for aspiration, difficult ventilation, or loss of the airway should optimally be intubated. However, the LMA Supreme, even more so that the Unique, is a good rescue airway because it does allow higher peak pressures and the ability to suction the stomach. When ventilation is needed and intubation is not possible, this is a very good option.
What Size Should I Use?
There are sizing charts and I attached one from the official LMA website. However, be aware that the body weight size chart is really designed for ideal body weight. In my experience, a 300 lb (136 kg), 5 ft tall (1.5 m) woman will not take a size 5 in either type of LMA.
Consider the ideal body weight, the size of the mouth and chin, and the length of the neck. If you hold the LMA Supreme to the side of the patient’s face with the bite block positioned at the level of the palate, then the distal tip of the mask should reach the level of the cricoid cartilage.
Insertion Technique For the LMA Supreme
Insertion is similar to inserting a Unique LMA, however the fixed curve and rigidity dictate some modifications.
Deflate the cuff and lubricate the back palate facing surface. Don’t lubricate the bowl of the cuff or the ventilation tube: the patient could aspirate the lubricant.
Open the mouth as wide as you can during insertion. The Supreme mask is quite large and inflexible compared to the mouth opening. Make sure that the tongue is pushed down, out of the way. A tongue blade is helpful for this. Use your index or ring finger to keep the lips out of the way as the LMA enters the mouth.
Look at the curve of the device. Aim the curve at the palate. Rotate the device against the palate and around the tongue until you feel the cuff seat against the upper esophageal sphincter in the lower posterior pharynx.
If the tongue gets trapped in the bowl of the device, don’t force it in. Gently free the tongue before you push the device into the posterior pharynx.
In order to accommodate the rotational curve that the Supreme must follow, you may need to have the patient positioned slightly ramped, with the head higher than the chest. This is especially true in the morbidly obese patient, where the chest in a fully supine patient often rises quite high. In the absence of the need to protect the cervical spine, don’t hesitate to tilt the head forward or back or to pull the jaw forward if the device won’t make the turn.
Here is the official graphic on insertion technique from the LMA site.
Notice the impressive rotational movement necessary to insert the LMA Supreme.
Verifying Optimal Placement
With the Supreme, you will be verifying not only ability to ventilate (first seal), but also what the company calls optimal “Second Seal” against the upper esophageal sphincter.
First make sure you can ventilate and, if the patient is breathing spontaneously, that the patient can self ventilate through the device. Sometimes one occurs without the other if the epiglottis is trapped or the mask malpositioned.
After insertion, the taping tab should be positioned 1 to 2.5cm from the upper lip. If the taping tab is more than 2.5cm from the upper lip, the device may be too big.
If the taping tab is less than 1cm from the lip, the device may be too small. Make sure the taping tab is not in contact with the lip as excessive pressure could cause injury. Use your best judgment about whether to replace an LMA that seems too big or small. Look at how well the patient is ventilating and consider the risks of replacement vs the gain.
To check Second Seal, apply about 1⁄4 inch of (viscous) water soluble sterile lubricant to cove the top of the proximal end of the drain tub. If probably seated, when you manually ventilate the gel should remain covering across the top of the drain tube. It should not bubble or blow off. If it does blow off insert the LMA more deeply and check again.
Risks Of Using the LMA Supreme
Because the LMA Supreme is stiffer, and slightly more bulky than the Classic, placing the Supreme requires a little extra caution.
It can be harder to insert in the patient with a small mouth. I find that I sometimes need to use a size smaller than the size predicted by body weight. Look at the size of the mouth and chin.
Potential to injure the lips and teeth is greater therewith the Classic unless you are gentle. Unlike the soft, flexible Classic LMA which can mold over and around the lips and the tongue during insertion, the Supreme is wider and inflexible. The Supreme has a tendency to roll the upper lip over the upper teeth and pin it there between the teeth and LMA. Teeth are designed to cut meat and are very good at their job. Because the tube is rigid, enough force can be placed on the trapped lip to lacerate it. I have seen one case where the cut was deep enough that a stitch was needed to close the laceration.
The tongue can get trapped in the bowl of the device. If forced backwards, the LMA you can potentially lacerate the frenulum (the vertical band of tissue attaching the base of the tongue to mucosa of the floor of the mouth). This is a painful injury.
Any LMA can dislodge a loose tooth, but the Supreme, because of its stiffness, carries more risk.
Occasionally you will find a patient where the Supreme simply will not turn the corner. Patients with large tongues, short chins and/or lingual tonsils come to mind. A Classic LMA will often, but not always, fit in these patients.
Ease of insertion, presence of a gastric port, and the option for using higher ventilatory pressures make the LMA Supreme more versatile and applicable for use in higher risk patients. However it’s essential to recognize the differences between the Supreme and the Classic in order to optimize positioning in the oropharynx and to avoid patient injury.
May the force be with you.