Obesity as a Focus in Anesthesiology Research Between 2000 and 2014: An Unmet Need?

| March 1, 2016

This ongoing column is written by members of the International Society for the Perioperative Care of the Obese Patient (ISPCOP), an organization dedicated to the bariatric patient.

Column Editor: Stephanie B. Jones, MD

Dr. Jones is Associate Professor, Harvard Medical School and Vice Chair for Education, Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel, Deaconess Medical Center, Boston, Massachusetts.

This month:

by Ingrid Moreno-Duarte, MD, and Roman Schumann, MD

Ingrid Moreno-Duarte, MD, and Roman Schumann, MD, are from Tufts Medical Center in Boston, Massachusetts

Bariatric Times. 2016;13(3):19–21.

Objective: We aimed to document and quantify the number of abstracts and published citations regarding anesthesia studies of patients with obesity. We also sought to identify areas for future studies of patients with obesity undergoing anesthesia.
Design: Observational study.
Setting: Abstracts from scientific meetings of the International Anesthesia Research Society (IARS) and the American Society of Anesthesiologists (ASA) and publications referenced in PubMed from 2000 to 2014.
Measurements: We searched the annual meeting abstract databases of the IARS and the ASA from 2000 to 2014 using the following search terms: “anesthesia” and “obesity,” “obese,” “overweight,” “bariatric,” “sleep apnea,” and “BMI.” Data collected included the number of abstracts per year, the country of origin, the type of research, and topic areas of study.
Results: From 2000 to 2014, the IARS and the ASA accepted 4,315 and 23,566 abstract submissions, respectively. Of these, 94 (2.2 %) from the IARS and 537 (2.3 %) from the ASA were obesity-specific abstracts. We discovered a noticeable single annual increase in 2007 for the ASA that preceded a publication spike in 2009 as reported in PubMed. Most of the studies were either retrospective in nature (ASA: 153/537; 28%, IARS: 27/94; 28%) or prospective observational (ASA: 235/537; 44%, IARS: 37/94; 39%) with fewer prospective randomized studies or basic-science studies.
Conclusion: This study shows a relatively constant obesity abstract publication rate close to two percent for the ASA and the IARS from 2000 to 2014, with a spike in 2007 for the ASA, and a relatively stable course for the IARS. Gold standard, prospective, randomized trials have a low frequency, and the specialty of anesthesiology should address this shortcoming in future years.

The prevalence of obesity is increasing worldwide, posing a special challenge for anesthesiologists, surgeons, and the entire perioperative care team as an increasing number of surgical patients with obesity will require anesthesia and surgical services.

Patients with obesity often have multiple comorbid conditions, including sleep disordered breathing and metabolic syndrome, complicating the clinical presentation and management. Physiologic changes secondary to obesity, such as decreased functional residual capacity and expiratory reserve volume that lead to increased work of breathing, oxygen consumption, CO2 production, and ventilation-perfusion mismatching, must be taken into account when preparing the perioperative plan. Patients with obesity have a potential for difficult mask ventilation and intubation complicated by rapid desaturation during periods of apnea. It is controversial whether obesity per se is predictive of difficult intubation as two large prospective, observational studies reported similar rates of difficulty with intubation, with body mass index (BMI) above 35 kg/m2 only as a weak predictor.[1,2]

Obesity has become a common condition in patients presenting for surgery and anesthesia with a prevalence of approximately 30 percent in the general surgical population.[3,4] The complex physiology and growing perioperative prevalence of obesity has led to increasing concern within the perioperative clinician community; as a result, several societies within anesthesiology were formed to address this problem. They include the following: The International Society for the Perioperative Care of Obese Patients (ISPCOP), The Society for Anesthesia and Sleep Medicine (SASM), European Society for the Perioperative Care of the Obese Patient (ESPCOP); and Society of Bariatric Anaesthetists (SOBA) in the United Kingdom.

ISPCOP, initially formed in 2005, was reconvened in 2010 and is dedicated to the perioperative care for adults and children with obesity across the entire spectrum of anesthesia services, including general surgery, offsite procedures, obstetrics and gynecology, and critical care. SASM formed in 2011, explores the challenge of sleep-disordered breathing that is often associated with obesity. ESPCOP and SOBA are also dedicated to clinical care, education, and research of the surgical patient with obesity.
Additionally, the Accreditation Council for Graduate Medical Education (ACGME) now offers a fellowship in sleep medicine for anesthesiologists and specialists interested in this field.

It is unclear whether the ongoing obesity epidemic and its resulting concerns have received a parallel increase of attention in anesthesiology research, either in the form of original research or abstract submissions to scientific meetings. Therefore, we aimed to determine the impact of obesity on anesthesiology research over the past 14 years, and describe the type of research interest prompted by this condition.

In this observational study, we searched the annual meeting abstract online databases of the International Anesthesia Research Society (IARS) and the American Society of Anesthesiologists (ASA) from 2000 to 2014 using the following search terms: “anesthesia and obesity;” “anesthesia and obese;” “anesthesia and overweight;” “anesthesia and bariatric,” “anesthesia and sleep apnea,” and “anesthesia and BMI.” Each abstract underwent review for inclusion. We excluded clinically challenging case abstracts and case reports. Data collected include the number of abstracts per year, country of origin, research design, and clinical outcomes reported. In addition, we searched the number of annual publications in PubMed with the terms “anesthesia obesity,” “perioperative obesity,” and “surgery bariatric obesity.” We used descriptive statistics to summarize our findings.

ASA and IARS abstracts were available as of 2000 and 2003, respectively. Between 2000 and 2014, the IARS and the ASA accepted a total of 4,315 and 2,3566 abstracts, respectively, with 94 (2.3%) and 537 (2.2%) of those abstracts specific to obesity (Figure 1). Since 2000, the relative annual number of abstracts steadily increased from 0.66 percent in 2000 to 3.5 percent in 2014 in the ASA database (Figure 2), whereas the IARS experienced greater fluctuation without a discernible trend. The majority of abstracts originated from North America followed by Europe and Australasia (Figure 3).

Clinical outcomes were explored in 28 percent (IARS) and 33 percent (ASA) of the abstracts, and topics included difficult airway and ventilation, difficult extubation, obstructive sleep apnea, pain control, surgical times, hospital length of stay, morbidity and mortality, and functional outcomes on discharge (Figure 4). Only six studies (IARS:2; ASA:4) explored the economic burden of obesity. The distribution of the study design categories was similar between societies (Figure 5).

In the PubMed repository, bariatric surgery publications had an exponential increase (from 60 annually to 1,100 annually in 2014), whereas anesthesiology related articles (34 annually to 140 annually) and perioperative obesity articles (21 annually to 182 annually) had a modest growth (Figure 5).

Every year, an increasing number of patients with morbid obesity undergo surgery and anesthesia. Patients with obesity often present a higher perioperative risk compared to their non-obese counterparts,[5] and pose a special challenge for the anesthesiologist as well as the perioperative care team. These patients require a detailed evaluation of their airway, cardiopulmonary, and endocrine status. Considering the complexity and increasing prevalence of these patients within the surgical population, our study surprisingly shows modest growth in research interest within the anesthesiology community over the past 14 years. This is in contrast to bariatric surgery publications tracked in PubMed, which had an exponential growth during the same period. Evidence-based perioperative anesthesia care recommendations for patients with obesity and morbid obesity are nascent and better developed for standardized surgical environments, such as bariatric surgery. Our exploration demonstrated an unmet need for anesthesiology to embrace perioperative care research for patients with obesity. In addition, thoughtful, prospective, high-quality studies are needed to further understand and improve care to these patients.

Despite a prevalence of perioperative obesity of approximately 30 percent, an average of just above two percent of scientific abstracts at the IARS and ASA were obesity related in the last 14 years. The relative number has increased annually for the ASA meeting only. The clinical outcomes studied reflect clinicians’ concerns with obesity. More prospective, randomized, controlled and basic science studies are needed. Obesity-related articles concerning perioperative and anesthesia care in PubMed have increased modestly compared to surgical obesity-related literature, indicating that obesity focused research in anesthesiology is an unmet need. The exponential rise in bariatric surgical manuscripts alone during the same period likely mirrors bariatric surgical growth and evolution in techniques, possibly providing more attractive research targets for the surgical specialty within this population compared to anesthesiology concerns. Further studies should address the disparity between the high perioperative obesity prevalence and the limited number of obesity-related research in anesthesiology as evidenced by scientific abstracts at the ASA and IARS. We conclude that a call to action is warranted.

1.    Heinrich S, Birkholz T, Irouschek A, Ackermann A, Schmidt J. Incidences and predictors of difficult laryngoscopy in adult patients undergoing general anesthesia : a single-center analysis of 102,305 cases. J Anesth. 2013;27(6):815–821.
2.    Lundstrom LH, Moller AM, Rosenstock C, Astrup G, Wetterslev J. High body mass index is a weak predictor for difficult and failed tracheal intubation: a cohort study of 91,332 consecutive patients scheduled for direct laryngoscopy registered in the Danish Anesthesia Database. Anesthesiology. 2009;110(2):266–274.
3.    Dindo D, Muller MK, Weber M, Clavien PA. Obesity in general elective surgery. Lancet. 2003;361(9374):2032–2035.
4.    Halvorson EE, Irby MB, Skelton JA. Pediatric obesity and safety in inpatient settings: a systematic literature review. Clin Pediatr (Phila). 2014;53(10):975–987.
5.    Glance LG, Wissler R, Mukamel DB, LI Y, Diachun CAB, Salloum R, Fleming FJ, Dick AW. Perioperative outcomes among patients with the modified metabolic syndrome who are undergoing non-cardiac surgery. Anesthesiology. 2010;113:859–872.

Funding: No funding was provided.

Disclosures: This study was financially supported by the Department of Anesthesiology, Tufts Medical Center, Boston, Massachusetts.

Category: Anesthetic Aspects of Bariatric Surgery, Past Articles

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