More Risk Factors for Supraglottic Airways in Obese Patients

Author: Michael Vlessides

Anesthesiology News

Severely obese patients who receive supraglottic airways are presenting with markedly more risk factors than their lower weight counterparts. Still, the choice to use these airway devices may be the correct one.

A study found that patients with a body mass index (BMI) of 35 kg/m² have a higher comorbidity composite, airway abnormality score and aspiration risk index than those with a BMI of less than 35 kg/m²—factors that ultimately may limit the elective use of supraglottic airways during general anesthesia in these individuals.

“As we know, obese patients often present with multiple comorbidities and the potential for difficult airway,” said Wejdan Battarjee, MD, an anesthesiology resident at Tufts Medical Center, in Boston. “As such, the decision to perform a supraglottic airway during general anesthesia in these individuals may be influenced by their comorbidities, airway abnormalities and aspiration risk. So, in our study, we hypothesized that severely obese patients receiving a supraglottic airway would score higher in all three of these domains than would patients with a lower BMI, and therefore present at greater risk of complications.”

Dr. Battarjee and her colleagues reviewed the records of 1,915 patients who electively received a supraglottic airway during general anesthesia at their institution. A variety of data were collected, including patient demographics, prevalence of obstructive sleep apnea and procedure duration.

Patient records were evaluated using three assessment scales: an 8-point comorbidity composite (excluding ASA physical status classification), a 4-point aspiration risk index and an 8-point airway abnormality score. The study population was then classified according to BMI: less than 35 kg/m², or 35 kg/m² or greater.

Of note, there were significantly more women in the high-BMI group than the low-BMI group (63.8% vs. 50.5%; P<0.005). Patient age was comparable between the groups, as was procedure duration.

The researchers also determined intraoperative complications; postoperative complications; and the incidence of airway interventions, such as change of supraglottic airway size or change to endotracheal intubation. Unpaired t-test and Pearson’s chi-squared test were used, as appropriate, for comparisons between groups.

As Dr. Battarjee reported at the 2018 annual meeting of the American Society of Anesthesiologists (abstract A2269), patients with a BMI of 35 kg/m² or greater had a significantly higher prevalence of obstructive sleep apnea and higher comorbidity composite, aspiration risk index and airway abnormality score (Table).

Although uncommon, airway interventions were also significantly more frequent in the higher BMI group. A change in supraglottic airway size was required in 3.02% of patients with a BMI of 35 kg/m² or greater, compared with 2.62% of those with a BMI less than 35 kg/m². Similarly, changes to endotracheal intubation were required in 2.01% of high-BMI patients and 0.35% of low-BMI patients (P=0.008).

Defining Safety Limits

Despite these differences, no intraoperative or postoperative airway complications were reported in either group.

“Comorbidity composite, airway abnormality score and aspiration risk index comprise clinical parameters that may influence or limit the use of supraglottic airways in general anesthesia,” Dr. Battarjee said. “In our study, use of the supraglottic airway occurred across a wide range of body mass indices, comorbidity composites and airway abnormality scores, and aspiration risk indices.”

She added, “We also believe that further research is needed to determine the limits of safety for supraglottic airways.”

As Dr. Schumann explained, the study offers insights into practice patterns that ultimately may improve patient care. “Many of us have concerns when we’re presented with a sick patient with certain risk factors,” he said. “In these cases, are we still going to use supraglottic airways or not?

“We used BMI to determine if obese patients present with different risk burdens, which they do,” Dr. Schumann continued. “Nevertheless, we need to remember that the decision to use the device doesn’t level the playing field for comorbidity burden between heavier and lighter patients; they are clearly higher in the obese group.”

The research highlights the fact that anesthesiologists, perioperative physicians and surgical intensivists are all faced with unique challenges when dealing with obese patients undergoing surgical procedures, according to session co-moderator Ashish K. Khanna, MD, an associate professor of anesthesiology at Wake Forest School of Medicine, in Winston-Salem, N.C. “Though there has been traditional hesitation with respect to using supraglottic airway devices for obese patients in view of the composite problems described, there has been a trend toward increased clinical use in the recent past,” Dr. Khanna said.

“This is very elegantly described by the work of the group from Tufts, where they show that the supraglottic airway was, in fact, used across a variety of BMI thresholds,” Dr. Khanna continued. “Though they report significantly more interventions in the heavier patient population, these numbers were overall very small in both groups, and are not unexpected at all. Moreover, there were no intraoperative or postoperative airway complications.

“Looking at this work reassures me that if I were to choose an LMA [laryngeal mask airway] or other supraglottic airway device for my obese patient in the operating room, I would not be making a wrong choice at all,” Dr. Khanna added. “This pilot study should prompt and encourage these investigators to conduct a large randomized trial—many thousands of patients would be needed—that would explore complications and outcomes associated with these devices.”