Sherif A. Andrawes, MD, FACG and Jean M. Chalhoub, MD
Generally, patients undergoing endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) are placed in the lateral decubital position as in regular upper and lower endoscopic procedures. However, throughout the procedure, position changes might be helpful for the endoscopist in reaching target lesions and aiding in resection. Ideally, the lesion should be located at a 6 o’clock position relative to the scope to achieve the shortest distance, an optimal stability, and a focused field between the distal tip of the endoscope and the target lesion. This optimal positioning can be difficult with some lesions and patient rotation can be considered to take advantage of gravity’s effect in separating lesions from dependent bowel walls, especially in the rectosigmoid and right colon. Also, in case of perforation, such positioning can minimize the possibility of fluids going through a perforated wall and allow easier endoscopic closure.1
The delicacy of therapeutic endoscopy relies on adequate control of all variables that might affect its success. In addition to the value of endoscopic skills, the importance of patient sedation is not to be underestimated as any movement or spasm resulting from inadequate patient sedation during the procedure might affect its time and success, and lead to serious complications like tissue injury and perforation.
The latest American Society for Gastrointestinal Endoscopy guidelines do not specify preprocedural fasting times for endoscopic procedures, and the literature has mixed data.2 However, the American Society of Anesthesiologists (ASA) guidelines recommend a 2-hour fast period after ingestion of clear liquids and 6 hours after ingestion of light meals prior to sedation.3 Given the prolonged durations of some endoscopic procedures and the probability of delayed gastric emptying in a subset of patients, the endoscopist should make sure enough time is allowed for gastric emptying prior to sedation to minimize aspiration risk and to avoid unnecessary delays. As far as elective resection procedures are concerned, acuity is rarely a concern, and thus procedure rescheduling can always be considered to circumvent unnecessary endotracheal intubations. In patients with achalasia undergoing per-oral endoscopic myotomy (POEM), residual contents can still be present in the esophagus despite an adequate fasting duration. In that case, the reverse Trendelenburg and rapid induction sequence can be considered to decrease the risk of aspiration.4
The depth of sedation is defined by the ASA’s Continuum of Sedation and includes 4 major levels. In minimal sedation or anxiolysis, patients are expected to respond normally to verbal stimuli, while in moderate or conscious sedation, they are expected to purposefully respond to verbal or light, tactile stimuli. Moderate sedation might minimally affect the patient’s airway, spontaneous ventilation, and cardiovascular function; however, those are usually maintained and no intervention is needed. In deep sedation, response is expected following repeated or painful stimulation, cardiovascular function is usually not affected, but airway intervention might be required as spontaneous ventilation can be inadequate. With general anesthesia, patients are unarousable even with painful stimulation, might have an impaired cardiovascular function, and usually require airway intervention as their spontaneous ventilation is often inadequate.3 Practically, patients might not fulfill all criteria pertinent to a certain sedation level as these are reference points on the complex sedation spectrum, and for that reason the ASA recommends that providers be amply trained in managing higher levels of sedation than the intended target sedation.3
Sedation administration can be performed either by endoscopists or by anesthesiologists through monitored anesthesia care (MAC) or general anesthesia. In the United States, endoscopist-administered anesthesia is only limited to moderate sedation usually with benzodiazepines (BZDs) and opiates because propofol use is allowed only under the care of an anesthesiologist. As a result of the growing preference for MAC in the United States, propofol use has been on the rise. Multiple studies show that propofol has an adequate safety profile in therapeutic endoscopies despite fears of its potential cardiopulmonary adverse events. A meta-analysis of 9 randomized controlled trials (RCTs) in 2013 concluded that propofol had a shorter recovery time, better sedation, and amnesia with no increase in adverse events rate when compared to traditional sedative agents.5 Similarly, a more recent meta-analysis that evaluated propofol use in routine and advanced endoscopic procedures in 27 studies including 2518 patients reached the same conclusions. In addition, there was no difference in adverse events rate when propofol was administered by the gastroenterologist (Nonanesthesiologist–administered propofol sedation [NAAP]) compared to an anesthesiologist (MAC).6 Given the complexity of advanced endoscopic resections, experts favor MAC over NAAP as it reduces endoscopist distractions and is thought to increase efficiency.
To achieve cost effectiveness and procedural success, a thorough patient assessment should be performed as part of preprocedural planning. In cases of repeat endoscopy for therapeutic purposes, the nature of the lesion and the planned technique of resection should be taken into consideration while deciding on the type of anesthesia. In addition, adverse events of anesthesia such as hypoxia, apnea, aspiration, and laryngospasm should be kept in mind. For that reason, reversal medications and the appropriate skills and tools for airway management are indispensable in any advanced endoscopy setting.
Risk Assessment, Patient Stratification, and Endotracheal Intubation
Preprocedural planning should include a thorough patient history and physical examination to risk-stratify patients and their risks of developing sedation-associated adverse events. As far as patient history is concerned, a detailed medication list is crucial while arranging for a procedure, particularly for managing antithrombotic agents according to current guidelines. A history of any illicit drug use, alcohol use, and smoking status should be obtained as those can affect patient response to sedatives. Additionally, patients should be evaluated for any previous reaction to sedatives or anesthesia, any previous difficulties with positive-pressure ventilation or endotracheal intubation, any organ dysfunction with a focus on cardiopulmonary diseases (including obstructive sleep apnea [OSA], coronary artery disease, congestive heart failure, and valvular pathologies), and advanced rheumatologic or osteoarthritic spine disease as all these factors can increase the likelihood of adverse events.7 In women of childbearing age, a pregnancy test should be performed as some sedatives might be teratogenic.8
Similarly, physical exam features like obesity, dysmorphic facial features, oral abnormalities (such as in edentulous patients), neck and jaw abnormalities, and a long beard can make airway management challenging. The Mallampati classification predicts airway difficulty and is also a helpful tool along with the STOP-BANG score to predict OSA.
One of the commonly used patient stratification tools is the ASA Physical Status Classification System. Patients with any degree of severe disease (ASA ≥ 3) have been shown to be at increased risk of sedation-related adverse events, including increased probability of unplanned cardiopulmonary events.9–11 Of note, a recent double-blinded RCT examined premedication with glycopyrrolate prior to ESD and showed that it significantly improved the ease of the procedure and decreased the incidence of cough and secretion-induced hypoxemia.12 The results are promising but more trials are needed to assess the effectiveness of this premedication in higher-risk patients and those undergoing other advanced procedures.
Unlike general endoscopic procedures, endoscopies involving endoscopic resection are more likely to require endotracheal intubation. Criteria for endotracheal intubation should be based on the patient’s risk factors and the type and duration of the procedure to be performed. Patients more likely to require intubation include those with multiple risk factors mentioned above, mainly those with OSA, Mallampati classification ≥ 3, body mass index > 35, active gastroesophageal reflux disease or a history of aspiration, and those with an unstable cardiopulmonary status.
As far as procedures are concerned, EMR requires deep sedation to allow passage of its special endoscope through the laryngopharynx and for the retrieval of the resected specimen. In its early phases, ESD was performed only under general anesthesia with endotracheal intubation especially in cases of upper gastrointestinal (GI) lesions; however, technical advances and procedure familiarity have made it possible under moderate to deep sedation.13 If no patient risk factors are present, both EMR and ESD can be performed without the need for general anesthesia and endotracheal intubation; however, if an upper GI procedural duration of > 60 minutes is expected, some endoscopists prefer endotracheal intubation. A recent retrospective study of 297 patients suggested that performance of ESD in an operating room setting resulted in a shorter recovery period and a lower rate of desaturation but had no difference regarding adverse events rate compared to an endoscopy room setting.14
Alternatively, POEM involves delicate submucosal tunneling followed by myotomy and as result is expected to require a longer duration. Subsequently, general anesthesia and endotracheal intubation remain the standard of care to date.
Monitored Anesthesia Care
Compared to endoscopist-administered sedation, MAC has been associated with a greater risk of sedation-induced adverse events, including aspiration pneumonia in patients with ASA I to III, and higher rates of perforation in colonoscopies regardless of ASA class.15–18 Nonetheless, MAC is preferred in therapeutic endoscopic procedures for its ability to achieve higher levels of sedation leading to decreased patient mobility and consequently decreased endoscopist distractions, improving patient and endoscopist satisfaction, and increasing overall efficiency in the endoscopy suite.19,20 In concordance with the European Society of Gastrointestinal Endoscopy guidelines, for elderly patients and patients with any of the previously mentioned risk factors (ASA ≥ III, Mallampati classification ≥ 3), MAC is preferred given the higher risk of adverse events in prolonged advanced endoscopic procedures.21 In addition, in procedures requiring prone positioning like endoscopic retrograde cholangiopancreatography and POEM, airway as well as cardiopulmonary compromise might be minimized with MAC and airway intubation. The latest American Society for Gastrointestinal Endoscopy guidelines have recommended MAC for patients undergoing complex endoscopic procedures based on moderate quality evidence.2
Endoscopist-administered sedation in the United States is limited to moderate sedation usually with BZDs (commonly diazepam and midazolam) and opiates (usually meperidine and fentanyl). Almost all United States hospital protocols require a dedicated nurse for endoscopist-administered moderate sedation protocols. In case of inadequate sedation induction, antihistamines, dexmedetomidine, and droperidol, among others, can be used. In addition to amnesia and prolonged analgesia for hours after the procedure, one main advantage of sedation with BZDs and opiates is the availability of reversal agents in cases of any adverse events. Those agents are generally considered safe for moderate sedation in patients with ASA classes of III and below. On the other hand, these agents have a slower onset of action compared to propofol-based regimens, are difficult to titrate during long procedures, and might have limited efficacy in certain patient populations. Additionally, given the long procedure times in therapeutic endoscopies and the shorter effects of antidotes compared to that of BZDs and opiates, postprocedural monitoring should be extended to avoid sedation adverse events.22
As an alternative to BZDs and opiates, dexmedetomidine has been the subject of recent studies for its conscious sedation effects as well as its low rate of cardiopulmonary adverse events and short recovery period. A 2015 meta-analysis of 9 studies that compared dexmedetomidine and midazolam in GI endoscopy concluded that dexmedetomidine was safe and effective because it was associated with better sedation and fewer episodes of restlessness.23 A recent study by Nonaka et al24 showed that a gastroenterologist-administered combination of dexmedetomidine and propofol provided a safe and stable sedation. Patients receiving the combination regimen required a lower propofol maintenance dose and smaller number of propofol boluses compared to those receiving propofol alone for sedation.
Nonanesthesiologist-Administered Propofol Sedation
Another common method of sedation is NAAP, which is usually performed with aims of reaching moderate sedation. The sedation administrator’s only responsibilities are delivering sedation and monitoring the patient. Sedation can be given by a registered nurse (nurse-administered propofol sedation or NAPS) under the supervision of the endoscopist, or by a nonanesthesiologist physician. Balanced propofol for moderate sedation (BPS) is another effective option that involves the administration of a single dose of an opiate and BZD followed by propofol doses as needed to achieve target sedation. In addition to the quick induction (30 to 45 seconds) and short duration effects (4 to 8 minutes) of propofol, advantages of NAAP include cost effectiveness if performed by trained personnel.25 In addition, NAPS regimens have shown a low rate of anesthesia-induced adverse events and higher patient satisfaction rates compared to regimens of midazolam and narcotics.26–28 In addition to the advantages of NAPS, BPS has also been shown to decrease the risk of oversedation given the ability to delicately achieve the desired sedation depth with small doses of intermittent propofol boluses.29,30 However, the lack of a reversal agent for propofol in addition to its potency, which can rapidly deepen patient sedation, were the main reasons for its restricted use among anesthesiologists only in the United States. Nevertheless, this can be partially overcome in BPS, during which naloxone and flumanezil can be used.2
Moreover, increased vigilance regarding additional sedative use (like BZD and opiates) is required in prolonged therapeutic procedures as it can increase patient recovery times.
Main Equipment and Setup
The endoscope should be in place with an air valve, a suction valve and a biopsy channel cap. For large-polyp EMR and ESD, a distal attachment device commonly known as a cap is placed routinely on the tip of the scope. The cap is a transparent, plastic device of different sizes and shapes that is helpful in EMR and ESD to provide endoscope stability, a fixated working space, and a focused field from the distal tip of the endoscope and the resection site of the mucosa. It is also helpful for localization of bleeding vessels under water irrigation (Figures 9-1 and 9-2).31,32 Caps are size specific for a particular scope and that can be found on the labeling material. It is placed according to manufacture specification. The endoscopist can select the individual cap based on personal preference.
The ergonomics and the room setup are very critical for advanced procedures like EMR and ESD. Figure 9-3 illustrates the ideal room setup for an endoscopy suite.
For upper GI procedures, the standard gastroscope is routinely used. Some experts recommend the use of a double- or single-channel therapeutic scope. The additional channel and/or the larger channel diameter may provide certain advantages, including the use of an additional device, and more efficient irrigation and suction of liquid.33 For lower GI procedures, the standard colonoscope is commonly used; however, some endoscopists prefer the pediatric size colonoscope, especially for lesions in the right colon and hepatic flexure, as retroflexion is commonly needed. Some experts recommend the use of a standard size gastroscope or a double-channel scope for rectal and left-sided lesions, as it is more flexible to use because resection of those lesions can be performed in a retroflexed position. The double-channel gastroscope has been used for difficult colonic EMR as it may provide the benefit of simultaneous use of forceps to grab a polyp and facilitate snare polypectomy, or to reduce the total procedure time by making use of both channels to inject and cut concurrently.33,34