Gastrointestinal Endoscopy in the Office-Based Setting
Kai Matthes
Endoscopic procedures are typically performed in an office or ambulatory surgical center and rarely in a hospital operating room. A total of 2.8 million sigmoidoscopies and 14.2 million colonoscopies were performed in the United States in 2002 (1). This number has continued to rise exponentially along with the increased number of diagnostic and interventional procedures being performed.
An integral part of the practice of gastrointestinal (GI) endoscopy is adequate sedation and analgesia. The level of sedation required depends on the type of endoscopic procedure being performed. Most endoscopies are performed with patients under “conscious sedation.” At this level of consciousness, the patient is able to make a purposeful response to verbal or tactile stimulation, and both ventilatory and cardiovascular function are maintained. There are instances that require a greater depth of sedation that can lead to general anesthesia.
To clarify this point, the American Society of Anesthesiologists (ASA) has classified four “levels” of sedation (see Table 13.1). By comparison, patient responsiveness during “deep sedation” involves purposeful responses to painful stimuli only. Airway support is sometimes required to maintain sufficient oxygenation (2). At the level of general anesthesia, the patient is not arousable, even to painful stimuli. Airway support is frequently required and cardiovascular function may be impaired (2, 3, 4).
Sedation for upper GI endoscopy is considered safe, with only minimal risk for the patient. However, cardiopulmonary complications may account for more than 50% of all reported complications. Most of these incidents are based on the following:
Vasovagal episodes
Oversedation
Hypoventilation
Aspiration
A prospective survey of 14,149 upper endoscopies indicated that the rate of immediate cardiopulmonary incidents was 2 per 1,000 cases with a 30-day mortality rate of 1 per 2,000 cases (7). A retrospective review of 21,011 procedures found the rate of cardiovascular complications was 5.4 per 1,000 procedures (8). The reported complications varied from mild transient hypoxemia to severe cardiorespiratory compromise and death.
To ensure patient safety, regardless of where the procedure is performed, if any anesthesia is utilized strict adherence to ASA standards for the anesthetic preparation, patient monitoring, and technique is recommended (see Chapter 5). In addition to the details mentioned in the preceding text, the American Gastroenterological Association (AGA) also established a standard that an anesthesia risk class should be documented for each patient receiving intravenous sedation, using the ASA score (30). Simply stated:
Table 13.1. Continuum of depth of sedation—definition of general anesthesia and levels of sedation/analgesiaa | ||||||||||||||||||||||||||||||
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CHOICE OF ANESTHETIC REGIMEN
Anesthetic Technique
Sedation and anxiolysis have in the past been administered by the endoscopist; however, it has become increasingly more common to have an anesthesiologist present during these procedures.
Sedation for GI endoscopy is particularly challenging because of the variability in long nonstimulating periods with intermitted peak stimulating events. Some endoscopic procedures may be undertaken without sedation. Most of the cases are performed under a monitored anesthesia care (MAC) anesthetic but occasionally general anesthesia is required for patients who are unable to tolerate these procedures under sedation alone.
The following patient characteristics were associated with tolerance of upper endoscopy or colonoscopy, with little or no sedation in a number of clinical trials:
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Less well studied are the factors that predict which patients are prone to experience great difficulty with sedation. The characteristics of “difficult to sedate” patients are recognized by most experienced endoscopists (see Box 13.1).
Box 13.1 • Increased Anesthetic Requirement
A history of prior difficulty with conscious sedation
Prescribed or illicit benzodiazepine or opiates use
Heavy alcohol use
Monitored Anesthesia Care
MAC requires intensive monitoring by trained individuals. Related risk factors, the depth of sedation, and the urgency of the endoscopic procedure play important roles in determining whether or not an anesthesiologist is consulted. The choice of medication for deep sedation during endoscopic retrograde cholangiopancreatography (ERCP) is largely operator dependent, but generally consists of sedatives such as propofol or a benzodiazepine used either alone or in combination with an opiate. The most commonly used benzodiazepines are midazolam and diazepam, favoring midazolam because of its fast onset, short duration, and high amnestic properties. Doses are titrated to patient tolerance depending on age, other illnesses, use of additional medications, and the sedation requirements of the particular procedure. For prolonged therapeutic procedures, such as ERCP, propofol
has been demonstrated to be advantageous when compared with standard benzodiazepine/narcotic sedation in terms of faster onset, deeper sedation, and faster recovery (2,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20). Deep sedation requires intensive monitoring by individuals trained in emergency resuscitation and airway management. (see Chapter 5)
has been demonstrated to be advantageous when compared with standard benzodiazepine/narcotic sedation in terms of faster onset, deeper sedation, and faster recovery (2,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20). Deep sedation requires intensive monitoring by individuals trained in emergency resuscitation and airway management. (see Chapter 5)
Table 13.2. Anesthetics | |||||||||||||||||||||
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