Cuff pressure when using a laryngeal mask (LM) for general anesthesia tends to be too high, which can result in postoperative adverse events. But this problem can be corrected with careful routine monitoring, a recent study concluded.
The study, which presented findings from a quality improvement project at Children’s Hospital Colorado, in Aurora, was conducted in two phases. In the first phase, the researchers collected information on baseline cuff pressures of both endotracheal tubes (ETTs) and LMs to assess current practice. After collecting data on 61 patients undergoing general anesthesia with ETTs and 51 patients with LMs, they determined that an intervention was not necessary for ETTs, as the cuff pressures were generally satisfactory, with a mean pressure of 20 cm H2O. However, they found that cuff pressures with LMs were highly variable and often unacceptably high, with a mean pressure of 61 cm H2O.
In the second phase of the study, the investigators implemented the use of a pressure-regulated syringe (Tru-Cuff, AES) to monitor LM cuff pressures, while separately measuring pressures with a manometer (Cufflator, Posey). As a result of this intervention, which was used in 50 patients, cuff pressures in the LM group were reduced to a mean of 25 cm H2O, a significant reduction (P<0.0001) (Figure).
Christian Taylor, MD, a pediatric anesthesiologist at Children’s Hospital Colorado, conducted the study along with Robert Friesen, MD. Dr. Taylor said he was expecting the ETT cuff pressures to be relatively low and the LM cuff pressures to be high, but was taken aback by how elevated they were compared with baseline.
“With the use of the intervention, we were expecting that number to drop significantly, and it did, so I feel like we achieved our goal for the project, which was to reduce that uncertainty about LM pressures,” he added.
Dr. Taylor also described the syringes used for each type of cuff, noting that both had “green zones” indicating acceptable pressures and “red zones” indicating that the pressure was too high. He noted that the green zone for the ETT syringe entailed 20 to 30 cm H2O—similar to the perfusion pressure of the tracheal mucosa—while that of the LM syringe comprised 40 to 60 cm H2O. Dr. Taylor pointed out that the LM pressures he and Dr. Friesen sought in the second phase of the study were in the range of 20 to 30 cm H2O—much lower than typically indicated by LM manufacturers—which is why they recommend using manometry to check pressure.
“There are several articles in the literature that recommend routine use of manometry, in any form, to check the pressure of LMs, because they tend to be highly variable,” Dr. Taylor said. “And it’s known that if you have high pressures, that can lead to adverse events for patients, such as postoperative sore throat.
“Using a manometer is a relatively easy process to do; it only takes about two or three seconds,” he added. “We think that if providers made it a part of their routine practice, the risk of causing airway adverse events could be significantly decreased, which is why we did this project.”
Narasimhan Jagannathan, MD, associate professor of anesthesiology at Northwestern University Feinberg School of Medicine and an anesthesiologist at Ann & Robert H. Lurie Children’s Hospital and Northwestern Memorial Hospital, all in Chicago, said the findings were in line with his experience, and agreed with the recommendation that clinicians employ manometry when using LMs.
“The standard is such that most physicians tend to overinflate LMs and don’t regularly check cuff pressures, which I think is good practice,” Dr. Jagannathan said. “In terms of practicality, cuff monitoring devices are not readily available in every [operating room], which becomes a bit of an issue, when they should be used routinely, in my opinion.”
Dr. Jagannathan added that, as more evidence mounts, he believes routine manometry when using LMs will increasingly become standard clinical practice. He also hopes to see it become a part of training, and to see manufacturers lower recommended pressures on their products.
“I think there’s enough evidence, and as more continues to come, we’ll see more buy-in from clinicians,” he said. “This is a well-understood phenomenon among people who are interested in airway management, such as myself, but I think more publications may be necessary for general anesthesiologists who are not specifically involved with the airway.
“But I think, in general, all anesthesiologists are concerned with this issue,” Dr. Jagannathan added. “Postoperative sore throat and other adverse events tend to stick around. It can be inconvenient for patients and their families, and I think it’s something that can be avoided in the first place.”
The findings were originally presented at the 2017 meeting of the Society for Pediatric Anesthesia/American Academy of Pediatrics Section on Anesthesiology and Pain Medicine (abstract AET-20).