A recent case involving two anesthesiologists and a Certified Registered Nurse Anesthetist found two of the three physicians responsible for their decision to utilize a laryngeal mask airway (LMA) and general anesthesia after the failure of managed anesthesia treatment in a morbidly obese patient. The case included a 44-year-old lady with a BMI of 49 kg/m2, a history of gastroesophageal reflux illness, and diabetes who was scheduled for elective hernia surgery. 1
Following LMA installation, the patient aspirated. The case was soon terminated when an endotracheal tube was placed. Although the patient lived, he had significant brain impairment. The plaintiff and her spouse were awarded $10,541,808. 1
This instance demonstrates the need of doing research on the usage of LMAs in morbidly obese people.
Anesthesia physicians often meet morbidly obese patients (BMI > 35 kg/m2).
Heart disease, hypertension, diabetes, asthma, obstructive sleep apnea, fatty liver, cancer, osteoarthritis, and gastro-esophageal reflux are all common comorbidities for these people.
Obesity raises the likelihood of airway issues such as difficult mask breathing, laryngoscopy, intubation, and aspiration.
Patients who are morbidly obese are often regarded as having “full stomachs,” and their airways are managed using an endotracheal tube.
The LMA is now a viable option for patients who have a restricted airway.
The LMA has also established a solid foothold in contemporary anesthetic practice, owing to its simplicity of installation and effectiveness, and is now utilized in patients undergoing diagnostic and therapeutic procedures that do not need tracheal intubation. 8
These devices are less stimulating than endotracheal intubation, easier to use for the provider than a face mask, and have a lower risk of problems such as teeth damage than an endotracheal tube.
Despite its popularity, LMA usage may result in potentially catastrophic problems.
In comparison to endotracheal tubes, LMAs may provide less protection against aspiration.
Selecting the safest airway device and method for anesthesia is critical to providing high-quality anesthesia treatment.
Providers of anesthesia have a responsibility to minimize risk and damage to patients. Due to the increased risk of anesthetic-related problems in morbidly obese patients, anesthesia physicians must exercise extreme caution while anesthetizing these individuals. The systematic evaluation of the literature examines the safety and effectiveness of utilizing an LMA in morbidly obese individuals.
Materials and Procedures
• The PICO Conundrum. To discover evidence addressing a clinical issue, the PICO framework is employed (patient or population, intervention, comparison, and outcome). The PICO question that guided the evidence search was as follows: Is an LMA (intervention) a safe and effective (outcome) alternative to endotracheal intubation (comparison) for morbidly obese people (BMI > 35 kg/m2) presenting for surgery (patient)?
• Search Techniques. PubMed and The Cochrane Database of Systematic Reviews were used to perform the evidence search (2005–2015). Intubation, laryngeal mask airway, laryngeal mask airway problems, and airway management in obese, morbidly obese patients undergoing surgery were among the search keywords and phrases used. We included systematic reviews with and without meta-analysis, as well as randomized controlled clinical trials (RCTs) that were not included in systematic reviews that satisfied the search criteria. Observational studies and case reports were eliminated. Additionally, we omitted sources that examined juvenile individuals, people with a history of problematic airway management, or the use of LMA in a resuscitation scenario or as a resuscitation assistance during endotracheal intubation.
Only English-language, full-text, peer-reviewed sources were used as evidence. These publications compared LMAs such as the LMA Classic (Teleflex Inc) and subsequent generations of LMAs with endotracheal intubation in obese persons undergoing general anesthesia.
The outcomes were safety, as measured by the rate of aspiration, and effectiveness, as measured by the facilitation of sufficient breathing. We included articles that examined both obese and morbidly obese people due to a predicted dearth of information investigating just severely obese subjects.
Melnyk and Fineout-technique Overholt’s was used to assess the evidence.
• Description and adequacy of the sources of evidence. The search identified twenty possible sources, but only two (12,13) met the inclusion requirements (Tables 1 and 2). These included a systematic review by the Cochrane Collaboration12 and an RCT13 that met the inclusion criteria but was not included in the Cochrane Collaboration systematic review. Both 12 and 13 were written by writers based outside the United States. Subjects had a BMI more than 30 kg/m2, but no source included entirely severely obese individuals (BMI > 35 kg/m2).
• Systematic Review by the Cochrane Collaboration. The Cochrane Collaboration’s systematic review included two studies. The search approach and evaluation procedure were detailed in detail. Only RCTs were considered, and the overall quality of the evidence was determined using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.
In one experiment, patients received gastric banding, whereas in the other, they had a variety of surgical procedures. Both studies evaluated the ProSeal LMA (PLMA, Teleflex Inc) in comparison to an endotracheal tube.
There were 232 patients with a BMI more than 30 kg/m2.
As expected, no source investigated just extremely obese individuals. Both studies included in the systematic review excluded patients having a suspected or proven history of difficult airway or gastro-esophageal reflux, and one study excluded any subject with stomach ulcers.
One RCT included data on patients’ sleep apnea scores, type 2 diabetes, hypertension, and depression, as well as whether they were using -blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, or antidepressants.
In one experiment, the same two anesthesia practitioners inserted the PLMA precisely, and they had expertise inserting more than 5,000 PLMAs.
In the other trial, the anesthesiology providers and their expertise were not explicitly identified.
Each source reported on subject randomization.
Anesthesia practitioners were not blinded to the airway devices, and there was no mention of an uniform insertion technique or LMA size.
Both the time required and the simplicity with which the airway device was inserted were noted.
According to the authors of the systematic review, three participants were eliminated from one of the RCTs due to device placement failure and laryngospasm, while four subjects were excluded from the other RCT due to device placement failure and one laryngospasm.
In the RCT, measurements of insufflation, end-tidal carbon dioxide capnography, peripheral oxygen saturation as measured by pulse oximetry (Spo2), heart rate, mean arterial blood pressure, and peak inspiratory pressures were taken at baseline, 1 minute, and 5 minutes after the airway device was removed, as well as in the postanesthesia care unit. In the other RCT, oxygen saturations were measured during surgery and in the postanesthesia care unit. Pulse oximetry was used to determine ventilation effectiveness, with hypoxemia defined as less than 92 percent Spo2.
Unsatisfactory placement of PLMA; oxygen desaturation intraoperatively, immediately postoperatively, and 30 minutes, 2 hours, and 24 hours later; pulmonary aspiration of stomach contents; laryngospasm; and bronchospasm were also reported as sequelae.
The other RCT included the following outcomes: change of airway device; hypoxemia intraoperatively, during insufflation, and in the postanesthesia care unit; pulmonary aspiration of gastric contents; laryngospasm on emergence; sore throat; hoarseness between surgery and discharge; and device placement time and success on the first attempt. According to the authors of the systematic review, the quality of evidence supporting these outcomes was poor to moderate. The RCT was omitted from the Cochrane Collaboration’s systematic review. The second source of evidence was an RCT that met the criteria for inclusion but was not included in the systematic review. These scientists compared the LMA-Unique (Intavent Orthofix Ltd) and i-gel LMA using a crossover design with 50 participants (Intersurgical Inc). Subjects were classified as slightly obese (BMI between 25 and 30 kg/m2) or moderately obese (BMI between 30 and 35 kg/m2). These participants were put in the supine position after undergoing surgery that lasted less than two hours. Exclusion criteria included a subject’s mouth opening being less than 2.5 cm, the presence of acute or chronic lung illness or neck pathology, and a risk of aspiration (gastro-esophageal reflux disease, hiatal hernia, full stomach, and pregnancy). Each airway device was inserted by the same two anesthetic practitioners, who were not blind to the device. The PLMA was inserted using a specified digital method and standard size (size 5), with time and ease of insertion noted.
Pulse oximetry was used to assess ventilation effectiveness, with hypoxemia defined as less than 92 percent Spo2 during and after operation. Before induction, after induction (during mask ventilation), after placement of the first airway device, and before and after insertion of the second airway device, heart rate, blood pressure, and Spo2 were recorded.
To evaluate leakage pressure, an audible leak test was performed using a stethoscope near the thyroid cartilage. Additionally, a pressure controlled ventilation test was performed. Ventilation began with a modest peak inspiratory pressure of 8 cm H2O and was gradually raised by 1 cm H2O every ten breaths until a maximum tidal volume of 10 mL/kg/min was obtained.
Following these tests, the second airway was installed and utilized throughout the procedure. Additionally, hypoxemia in the operating room or postanesthesia care unit, cough, sore throat, vomiting, laryngospasm, bronchospasm, and aspiration of stomach contents were outcomes of the RCT.
Both types of data analyzed clinically relevant results demonstrating the safety and effectiveness of the PLMA, LMA-Unique, and i-gel airways in obese individuals. Hypoxemia, effective placement, capacity to ventilate, presence of laryngospasm/bronchospasm, and aspiration were all considered adverse outcomes. Researchers concluded that the time needed for insertion and the ease with which an LMA was inserted in an obese patient had no therapeutic value. Although the risk of aspiration is increased for obese individuals having general anesthesia, no occurrences of aspiration were observed in the 282 participants. This might be because the studies were not powered to find between-group differences for this very uncommon incident. One of the studies included in The Cochrane Collaboration systematic review had sufficient power to identify changes in blood pressure, plasma norepinephrine levels, and oxygen saturation, while the RCT had sufficient power to detect variations in airway pressure in the presence of a leak.
• Hypoxemia postoperatively. According to the authors of a systematic study published by The Cochrane Collaboration, the mean oxygen saturation of peripheral blood in the postanesthesia care unit for the endotracheal tube group was between 90.3 and 94.7 percent. The PLMA group showed a 2.54 percent greater oxygen saturation than the control group. However, the evidence was graded as being of poor quality (low quality being defined as “additional research is extremely likely to have a significant influence on our confidence in the effect estimate and is likely to affect the estimate”). Significant improvements in oxygenation during and after surgery in the PLMA group compared to the endotracheal tube group suggested improved overall performance and less postoperative coughing, implying a faster recovery for patients.
• Success with Subjects With Difficult Airways. Five of 118 participants in The Cochrane Collaboration systematic study had their PLMA replaced with an endotracheal tube after the PLMA was unsuccessfully placed.
However, the quality of evidence was graded as poor in this systematic review conducted by the Cochrane Collaboration.
In the RCT, the i-gel LMA had considerably shorter insertion times and was easier to implant than the LMA-Unique.
Subjects with a Mallampati score of 3 or above had an increase in the difficulty and frequency of attempted insertions.
In the RCT, one occurrence of blood on the airway device was seen when the LMA-Unique was put first, followed by the i-gel airway.
Although none of the studies defined aspiration, neither the RCT nor the systematic review by The Cochrane Collaboration identified any instances of pulmonary aspiration in either of the study groups.
• Bronchospasm/Laryngospasm. The Cochrane Collaboration comprehensive review found that laryngospasm/bronchospasm occurred in two of 118 participants in the PLMA group and four of 114 subjects in the endotracheal tube group, although no major respiratory problems or fatality occurred within 30 days.
• Capacity for Ventilation The RCT compared leakage pressure by recording the tidal volume when an audible leak was detected up to a maximum of 10 mL/kg, with individuals in the i-gel group experiencing considerably greater leakage pressure. 13 In the i-gel group, 46% of patients attained the tidal volume; in the LMA-Unique group, 28% reached the tidal volume.
The authors of the RCT stated that “the i-gel may be utilized with greater airway pressures than the LMA-Unique and so may be used as a successful LMA in patients with mild to moderate obesity who have mouth openings smaller than 4 cm during elective short-term supine surgery.”
Both evidence sources included methodological problems and contradictions. No researcher included participants who were morbidly obese solely. The researchers evaluated three distinct classes of second-generation LMAs. This precludes broad generalizations regarding the safety and effectiveness of any LMAs or other supraglottic airways. Although neither evidence source’s authors mentioned aspiration as an issue, the evidence sources were likely underpowered to find differences in aspiration.
According to reports, the risk of aspiration associated with LMA usage is around 2 in 10,000.
15 Another group observed a greater rate of aspiration in participants receiving positive pressure ventilation through an endotracheal tube (1 in 4,394) than in persons receiving positive pressure ventilation via an LMA (1 in 4,394). (1 in 11,877). 15 It is unknown if any of these studies included participants who were obese or severely obese. The Cochrane Collaboration systematic study was the only one identified that compared the use of a PLMA to an endotracheal tube in obese people. These authors discovered that the difference in insertion time between a PLMA and an endotracheal tube was clinically insignificant in obese people.
Additionally, they said that an LMA would have a failure rate of between 3% and 5%. Once correctly positioned, this review concluded that a PLMA delivers at least as excellent oxygenation as an endotracheal tube and decreases postoperative coughing. The authors reported in the RCT that the i-gel was capable of much greater leakage pressures than the LMA-Unique.
The LMA is now included in the difficult airway protocol and is commonly utilized effectively in patients without significant comorbidities or aspiration risk, particularly in outpatient surgical settings.
New generations of LMAs are being developed or existing models are being changed to overcome LMA shortcomings.
The use of an LMA in obese and severely obese individuals for general anesthesia remains contentious due to safety concerns, including aspiration. In the United States, there is now case law establishing that an aspiration after LMA implantation in a morbidly obese patient in the outpatient environment resulted in a substantial compensation.
Additional big, high-quality trials must be done before LMA therapy in any obese patient is recommended.