Anesthesia for Colonoscopy

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 ).

Box 15-1

Guidelines for Anesthesiology Assistance During Gastrointestinal Endoscopy

Modified from American Association for Study of Liver Diseases; American College of Gastroenterology; American Gastroenterological Association Institute; American Society for Gastrointestinal Endoscopy; Society for Gastroenterology Nurses and Associates; Vargo JJ, DeLegge MH, Feld AD, et al. Multisociety sedation curriculum for gastrointestinal endoscopy. Gastrointest Endosc. 2012;76:e1-e25.

Prolonged procedure requiring deep sedation or general anesthesia

Anticipated intolerance to standard sedation regimens

Increased risk because of comorbidity (ASA 3 to 5)

Increased risk for airway obstruction (e.g., severe obstructive sleep apnea, stridor)

Dysmorphic facial features (e.g., Pierre-Robin, trisomy 21)

Oral abnormalities (e.g., macroglossia, small mouth opening, trismus)

Neck abnormalities (e.g., cervical stenosis, thick neck, trauma)

Uncooperative or pediatric patient

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.

Table 15-1

Continuum of Depth of Sedation

Modified from Gross J, Bailey PL, Connis R, et al. Practice guidelines for sedation and analgesia by nonanesthesiologists. Anesthesiology. 2002;6(4):1004-1017.

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.

Box 15-2

Predictors of Difficult Mask Ventilation and Difficult Intubation

Modified from El-Orbany M, Woehlck HJ. Difficult mask ventilation. Anesth Analg. 2009;109(6);1870-1880.

Increased body mass index (>30 kg/m ² )

History of snoring or sleep apnea

Presence of beard

Lack of teeth

Age greater than 55 years

Mallampati class III or IV

Limited mandibular protrusion

Male gender

Airway masses or tumors

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.

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