Bariatric Times

MAY 2018

A peer-reviewed, evidence-based journal that promotes clinical development and metabolic insights in total bariatric patient care for the healthcare professional

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8 Opinion Review Bariatric Times • May 2018 Patients with Obesity Need Not Routinely Undergo Rapid Sequence Anesthetic Induction BY JAY B. BRODSKY, MD Bariatric Times. 2018;15(5):8–10. ABSTRACT A "rapid sequence induction" (RSI) has been a routine part of the anesthetic management of patients with morbid obesity for over 40 years. A RSI consists of the rapid administration of a quick acting anesthetic induction agent and a paralytic in order to intubate the trachea as quickly as possible. Cricoid pressure is also applied in an attempt to reduce the risk of gastric aspiration. Recent evidence suggests that not only is RSI not needed for most patients with obesity, but it is probably ineffective in preventing aspiration and might also distort the airway making tracheal intubation more difficult. KEYWORDS Rapid sequence induction, morbid obesity, pulmonary aspiration, safe apnea period, cricoid pressure INTRODUCTION A "rapid sequence induction" (RSI) is a technique used by anesthesiologists to produce the rapid onset of general anesthesia and paralysis immediately prior to tracheal intubation in order to reduce the risk of pulmonary aspiration. The goal of RSI is to minimize the time between apnea with loss of protective airway reflexes and successful placement of a cuffed endotracheal tube. RSI consists of the intravenous administration in rapid succession of both a quick-onset anesthetic induction agent and a fast-acting muscle relaxant. Cricoid pressure is applied, and bag-mask ventilation is avoided. Many anesthesiologists continue to perform RSI as part of their routine management of all patients with obesity. There is increasing evidence that this practice is not only unnecessary but might actually be harmful. RSI IN CURRENT PRACTICE RSI is usually used before emergency procedures on non- fasted patients and for elective surgical patients who are believed to be at increased risk for pulmonary aspiration. Pulmonary aspiration is defined as the presence of bilious secretions or particulate matter in the tracheobronchial tree and/or the presence of an infiltrate on the postoperative chest roentgenogram that was not present preoperatively. The incidence of clinically significant aspiration for all surgical patients is extremely low, occurring in less than 3 in 10,000 general anesthetics. It is controversial as to whether RSI actually protects the airways from contamination. 1 Aspiration, when it occurs, is usually associated with emergency surgery, and almost all of these patients underwent RSI. A large meta-analysis concluded that there is no evidence to support or refute the efficacy of RSI in reducing aspiration. 2 Despite these findings, RSI is considered the "standard of care" for induction of anesthesia and tracheal intubation in patients believed to be at risk for aspiration. Aspiration risk factors include the presence of significant gastro- esophageal reflux disease (GERD), ileus, acute abdomen, term pregnancy, diabetes mellitus with autonomic neuropathy, impaired levels of consciousness, and patients with neurologic conditions causing loss of gag reflexes. These patients routinely undergo RSI. RSI AND PATIENTS WITH OBESITY RSI has been a part of the anesthetic management of patients with obesity for many years. 3 This practice was based on a study from 1975 that reported that fasting patients with obesity had larger volumes (>25mL) of more acidotic (pH<2.5) gastric fluid than similar patients who are lean. 4 Since the severity of the pneumonitis following aspiration depends on the volume and acidity of the material aspirated, obesity by itself was considered a risk factor. More recent studies have challenged these findings. The volume and pH of gastric fluid is identical in both subjects with obesity and normal weight. 5 The gastric contents of unpremedicated, non-diabetic fasting patients with obesity (body mass index [BMI] >30kg/m 2 ) without significant gastro-esophageal pathology are not different than other surgical patients. 6 A subset of patients with obesity and severe GERD or Type 2 diabetes mellitus with autonomic neuropathy (gastroparesis) might be at increased risk, but evidence of significant aspiration events for even these patients does not exist. Although some authors continue to recommend RSI for all surgical patients with morbid obesity, 7 there is increasing recognition that it is unnecessary in fasted patients with obesity without other risk factors. The European Society of Anaesthesiology and the American Society of Anesthesiologists have each published guidelines on reducing the risk of perioperative aspiration. 8,9 Both do not consider obesity to be a risk factor and recommend that patients with obesity who are without gastroparesis or symptomatic GERD follow the same fasting guidelines as patients of normal weight and be allowed to drink clear liquids up until two hours before elective surgery. The 4th National Audit Project (NAP4) reviewed airway management complications in the United Kingdom. Mortality from all causes was extremely rare—approximately one death in 180,000 general anesthetics. Gastric aspiration, the most frequent cause of anesthesia-related mortality, was reported to occur in a "disproportionate" number of patients with obesity. 10 However, NAP4 did not identify obesity as the aspiration risk, but rather found that complications occurred because of unfamiliarity by some anesthesiologists with the appropriate airway management of obese patients, including poor clinical judgment, failure to protect the airway by the inappropriate use of supraglottic airways, and not being properly prepared when difficulty with tracheal intubation occurred. Should RSI be performed on patients with obesity who have previously undergone bariatric procedures? There have been no reports of aspiration in patients who have had a gastric bypass or sleeve gastrectomy. Some studies do report development of new symptoms of GERD after sleeve gastrectomy, 14 while others report resolution of pre-existing reflux symptoms after the same operation. 15 Gastric bypass consistently results in long- lasting improvement in GERD, 16 and presumably a decrease in the risk of aspiration during subsequent anesthetics. There have been isolated case reports and one small series of patients who had a gastric banding who, despite preoperative fasting and an RSI, aspirated on induction of general anesthesia before subsequent operations. 11–13 This suggests that only those former bariatric patients who have had a gastric banding should undergo RSI. RISKS OF RSI AMONG GENERAL POPULATION Since pulmonary aspiration during general anesthesia is extremely rare, concerns have been raised as to whether the potential risks of RSI are greater than its presumed benefits. The 5th National Audit Project (NAP5) in the United Kingdom found that awareness under anesthesia occurred most often during the induction of anesthesia, Image originally published in case report/commentary by Drs. Jay B. Brodsky and Michael Margarson. Article can be accessed at https://psnet.ahrq.gov/webmm/case/221. Image used with permission from author.

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