History of Anesthesia for Gastrointestinal Endoscopic Procedures
Sedation and analgesia are common components to most upper and lower endoscopic procedures. Although diagnostic upper and lower endoscopy can be performed without sedation, the use of sedative medications improves patient comfort and the quality of the procedure. The use of sedation in part depends on the country and reflects local practices. The decision to include an anesthesiologist in the care of a patient with a gastrointestinal (GI) issue also may depend on the location of the procedure and ready availability of trained anesthesia staff. Anesthesiologists tend to be more involved in sedation when procedures are being performed in an ambulatory surgery center instead of an office-based setting, where resources are limited.
Since the U.S. Preventive Services Task Force mandated screening colonoscopies for all patients between the ages of 50 and 75 years, colonoscopies have become one of the most common medical procedures in the United States. In 2002 it was estimated that more than 14 million colonoscopies were performed. Although diagnostic colonoscopies can be done without sedation, the use of sedative medications improves overall outcomes — patients describe improved comfort, and proceduralists note that sedating the patient improves the diagnostic quality of the procedure. Sedation for endoscopy has traditionally been administered by a nurse or endoscopist; however, as the number and complexity of cases have increased, participation by a trained anesthesiologist has become more commonplace in the endoscopy suite. Anesthesiologists tend to be more involved in sedation when procedures are performed in an ambulatory surgery center as compared with an office based–setting, where there are limited resources.
General Considerations
General Reasons to Request an Anesthesia Provider
Several factors can contribute to the decision to use anesthesiology-based sedation for an endoscopic procedure. Certain patients commonly warrant anesthesiology-based care, including those with multiple or problematic comorbidities or airway concerns and pediatric patients. In addition, highly complex, long, or high-risk procedures are performed most safely under general anesthesia to prevent patient movement interfering with the procedure. Finally, patients with a history of failed gastroenterologist-administered sedation will benefit from the skills of a trained anesthesia provider ( Box 15-1 ).
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The majority of patients can tolerate endoscopic procedures without general anesthesia by titrating the level of sedation to achieve a safe balance between patient comfort and optimal procedure conditions. Most endoscopic procedures are performed with the patient under moderate sedation. Table 15-1 lists the criteria for varying levels of sedation.
| Signs | Minimal Sedation Anxiolysis | Moderate Sedation/ Analgesia | Deep Sedation/ Analgesia | General Anesthesia |
|---|---|---|---|---|
| Responsiveness | Normal response to verbal stimulation | Purposeful response to verbal or tactile stimulation | Purposeful response after repeated or painful stimulation | Unarousable even with painful stimulation |
| Airway | Unaffected | No intervention required | Intervention may be required | Intervention often required |
| Spontaneous ventilation | Unaffected | Adequate | May be inadequate | Frequently inadequate |
| Cardiovascular function | Unaffected | Usually maintained | Usually maintained | May be impaired |
Preoperative Evaluation
Patients must be evaluated for each procedure, with safety a top priority. Empty-stomach status must be confirmed with patients before proceeding with an elective procedure such as a colonoscopy. Preoperatively the anesthesiologist should always perform an airway examination. This includes evaluation for characteristics of difficult mask ventilation ( Box 15-2 ). Discuss with the patient all possible comorbidities associated with the sedation and anesthesia that will be used during the procedure. Ask the patient about previous experience with anesthetics, to identify patients who could be difficult to sedate or who could react poorly to sedation. Discuss what the patient expects from the procedure. Remember that patient comfort is an important factor in patient satisfaction for colonoscopies.
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Communication between the proceduralist and anesthesiologist is key to understanding how long the procedure will take and for ensuring that the patient will be able to tolerate sedation for the entirety of the colonoscopy. Older age in women, body mass index greater than 25 kg/m 2 , diverticular disease in women, and history of constipation in men are predictors of increased time to complete an outpatient colonoscopy. The anesthesia plan should be adjusted accordingly and always contain alternative options in the event the initial plan does not work.
Monitoring
The recent advancements in safety for patients undergoing anesthesia are due in part to improved monitoring. In the past several decades, key monitors have increased anesthesia safety. The basic monitors now mandated by the American Society of Anesthesiologists (ASA) to be used during all procedures requiring anesthesia, are electrocardiogram, blood pressure (noninvasive or invasive), end-tidal capnography, oxygen saturation, and temperature.
Additional monitors might be necessary on a patient-to-patient basis. For example, electroencephalographic (EEG) monitoring can be used to identify the depth of anesthesia to avoid awareness during general anesthesia, although the efficacy of EEG monitors for this indication is still debated. Continuous physical examination is the typical means of monitoring the depth of anesthesia for patients undergoing a colonoscopy. Ideally, patients should be able to verbally communicate with the anesthesia provider if provoked.
Positioning
Patient position is a particularly important consideration because many endoscopic procedures require the patient to be in the lateral or prone position, making it difficult if not impossible to access the airway if airway management techniques must be implemented. Therefore careful preoperative airway evaluation is paramount. If concern exists about airway management, the safest plan is to proceed with general anesthesia with endotracheal intubation, depending on the patient’s associated comorbidities.
Once the patient has been positioned for the procedure, all monitors should be checked to ensure they are working properly. In addition, functional intravenous access should be confirmed before the patient is handed over to the proceduralist.
Anesthetic Choices
Anesthesia providers have the ability to vary the amount of sedation necessary to ensure the patient gets through the procedure safely and comfortably. In devising the anesthetic plan, focus should be on the level of sedation necessary to achieve this goal (see Table 15-1 ). Monitored anesthesia care can be provided with the myriad medications listed in Table 15-2 .
| Effect | Midazolam | Fentanyl | Propofol | Ketamine | Dexmedetomidine |
|---|---|---|---|---|---|
| Amnesia | + | + >30mcg/kg/m | + dissociative | ||
| Analgesia | + | + | + | ||
| Anxiolysis | + | +/− | + |
In the outpatient setting, which is where most diagnostic colonoscopies are performed, the goal of care is to provide a safe and effective anesthetic, with minimal side effects and quick recovery. Combinations of anesthetic agents are often the best means of achieving this goal. For example, medications such as propofol, when used in addition to a short-acting opiate such as fentanyl, provide the ideal level of amnesia, anxiolysis, and analgesia. Combining propofol with other sedative medications can help reduce the amount of any one administered medication, thereby preventing propofol’s negative cardiovascular effects. In the preoperative period, take note of a patient’s anesthetic history to identify patients at risk for bad reactions or side effects with these medications. One effect of note is the patient who becomes extremely nauseous with opiates. In patients with a history of difficult sedation, ketamine has shown to be an effective adjunct in moderate sedation. In the inpatient setting, in which colonoscopies are in contrast to the outpatient setting, anesthesiologists are not limited by the expectation that the patient will be going home that day, so medications that have a longer-lasting effect, such as ketamine, are more readily used.
It is essential to maintain the airway of patients identified preoperatively as presenting with a potentially problematic airway. For these patients, the safest way to do the procedure might be general anesthesia with a protected airway. It is important to have this discussion preoperatively with the proceduralist and the patient.
Level of Sedation
The necessary levels of sedation to achieve safe and successful endoscopic procedures, ranging from no sedation to general anesthesia, are determined by patient-related and procedure-related factors. Patient-related factors include comorbidities, airway concerns, medication tolerance, and amount of pain or anxiety. Important procedure-related factors include patient position, type of procedure, duration, and complexity of procedure.
Patient position is a particularly important consideration, because many endoscopic procedures require the patient to be in the lateral or prone position, in which access to the airway becomes difficult, if not impossible, if airway management techniques must be implemented. Airway accessibility consideration increases during upper endoscopic procedures when the endoscope is advanced through the oral cavity. When concern for airway management exists, the safest plan is to proceed with general anesthesia with endotracheal intubation, often with a rapid sequence induction.
The majority of patients can tolerate endoscopic procedures without general anesthesia by titrating the level of sedation to achieve a safe balance between patient comfort and optimal procedure conditions. Most endoscopic procedures are performed with the patient under moderate sedation. Table 15-1 lists the criteria for varying levels of sedation. In the United States; interest is growing on the part of the insurers to have clear indications for the use of an anesthesiologist.
Pharmacology: Common Sedative Medications
The choice of sedative medication depends on the provider and should be based on a combination of the procedure being performed and the individual patient. Traditional sedation for endoscopies typically entails a combination of opioids and benzodiazepines, usually midazolam and fentanyl, respectively, administered under the supervision of the endoscopist. The diverse array of sedative medications can allow sedation to be tailored according to each individual patient’s needs based on the side effect profile of each medication (see Table 15-2 ).
Midazolam
Benzodiazepines have historically been the sedative agents favored by gastroenterologists. Along with their sedative effects, benzodiazepines have the added benefit of providing anxiolysis. Midazolam (Versed), in particular, is preferred because of its amnesic effects, fast onset, and short duration of action. When used alone, benzodiazepines have only modest hemodynamic effects. Initial dosing of 1 to 2 mg is standard for young, healthy adults and provides significant anxiolysis. Additional doses of 1 mg every 2 to 5 minutes can then be administered as needed throughout the procedure to achieve adequate levels of sedation. When midazolam is given in conjunction with an opioid, such as fentanyl, synergism reduces the amount of midazolam needed for sedation. Patients older than 60 years of age or classified as having ASA 3 or greater status often require smaller doses of midazolam for the same effect. Because the liver metabolizes midazolam, dose adjustments are also indicated in patients with significant liver disease.
The major disadvantage of midazolam is its respiratory depression, especially when given in combination with an opioid. The respiratory depressant effect can last up to 2 hours. However, benzodiazepines can be reversed with flumazenil, which competitively antagonizes the central effects on gamma-aminobutyric acid (GABA) receptors. In addition, paradoxical reactions to midazolam, including disinhibition and aggression, have been reported.
Fentanyl
Fentanyl is a short-acting synthetic opioid that is frequently given as an analgesic during endoscopic procedures. Its fast onset and short duration of action make it a better choice than other opioid analgesics, such as morphine or meperidine . Fentanyl in combination with midazolam is considered part of the “traditional” sedation approach used by endoscopists without the supervision of an anesthesiologist. Initial doses of 50 to 100 mcg can be supplemented with boluses of 25 to 100 mcg, based on the individual patient. As with benzodiazepines, the dose should be reduced for elderly and critically ill patients and with hepatic impairment. Fentanyl is also safe to use in the pediatric population, with an initial dose of 0.5 mcg/kg, up to a maximum initial dose of 50 mcg.
Common side effects of fentanyl are similar to the side effects of all opioid narcotics and include bradycardia and respiratory depression. The respiratory depressant effects can be reversed with naloxone if needed.
Propofol
Propofol has come into favor for use by endoscopists as a replacement for traditional sedation because it increases patient comfort and decreases recovery times. It also improves the diagnostic quality of the procedure. Propofol can be administered as an infusion or as intermittent boluses to achieve the desired sedation levels. Continuous infusions allow for easy titration to the desired level of sedation with relatively fast recovery after the infusion is terminated. Propofol may have significant advantages during more complex procedures, such as endoscopic retrograde cholangiopancreatography (ERCP), in which deep sedation is needed. Infusion rates for moderate sedation are 25 to 75 mcg/kg/min, but may be considerably less in elderly or critically ill patients. Propofol infusions for sedation may also cause some degree of amnesia, which can be beneficial to patient satisfaction. Finally, the antiemetic properties of propofol may be especially useful when providing sedation for upper endoscopic procedures. In the pediatric population, propofol is an effective regimen alone or in combination with other sedative agents.
The common side effects of propofol include hypoventilation, decreased muscle tone, cardiac depression, and hypotension. Therefore caution must be used when administering propofol as a sole means of sedation in patients who have significant cardiopulmonary disease or airway abnormalities.
Dexmedetomidine
Dexmedetomidine has more recently gained favor among anesthesiologists as an agent for inducing mild to moderate levels of sedation. As a nonselective alpha-2 receptor agonist, dexmedetomidine provides sedation, anxiolysis, and analgesia. Although its high cost can make it prohibitively expensive, it still may be a favorable sedative in patients with hypoventilation concerns because it has minimal effect on respiratory drive. It is not very effective as a sole agent for colonoscopy, but can be very effective when supplemented with fentanyl or other agents Dexmedetomidine is given as an optional initial bolus of 0.5 to 1 mg/kg over 10 minutes, followed by an infusion of 0.2 to 0.7 mcg/kg/hr.
The main concern with dexmedetomidine is that its sympatholytic effects can trigger significant hypotension and bradycardia. However, for endoscopic procedures, it can be used in conjunction with ketamine to blunt some of the hemodynamic consequences of sympatholysis.
Ketamine
Ketamine is unique in that is has both sedative and analgesic properties without impairing respiratory drive or cardiovascular tone. It is a useful sedation adjunct for complex procedures, such as ERCP or endoscopic ultrasound (EUS), or for difficult-to-sedate patients undergoing colonoscopy. Ketamine is frequently administered in combination with low-dose midazolam to prevent some of the hallucinogenic effects associated with ketamine administration. Ketamine boluses are also useful adjuncts to propofol or dexmedetomidine infusions because its stimulant effect on the respiratory and cardiovascular systems can counteract the cardiac and respiratory depressant effects of these agents. Bolus dosing of 0.1 to 0.3 mg/kg every 2 to 5 minutes, titrating to the desired effect, is a reasonable dose in a healthy adult, with a maximum dose of 1 mg/kg. Intramuscular or intravenous ketamine also can be useful in the pediatric population for sedation during endoscopic procedures.
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Anesthesia for Upper Gastrointestinal Endoscopy
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