The primary options a patient has for intravenous (IV) sedation during gastroenterological procedures include:  

• Procedural sedation ranging from mild anxiolysis to deep. In IV sedation, breathing takes place independently. The patient also remains responsive to stimuli. This form of sedation can be administered by the endoscopist or anesthesiologist with a nurse to monitor the patient’s state of consciousness and vital signs.
• General anesthesia. General anesthesia is a state of total unconsciousness resulting from general anesthetic drugs. A variety of drugs are given to the patient that have different effects with the overall aim of ensuring one or all of the following: unconsciousness, amnesia, analgesia and paralysis. This type of sedation suppresses the patient’s ability to breathe independently and he or she is unarousable during the procedure. General anesthesia requires the presence of an anesthesiologist.
• Monitored anesthesia care (MAC). This type of anesthesia service can cover the full range of sedation levels including general anesthesia. The service includes all aspects of anesthesia care including preprocedure visit, intraprocedure care, and postprocedure anesthesia management. MAC is indicated for some patients based on the nature of the procedure they are to undergo, their medical condition, or the potential need to covert to general anesthesia during the procedure. MAC differs from moderate sedation in that it is provided by an anesthesiologist who makes an assessment in advance of the actual or potential medical problems that may occur during the procedure. Additionally, the person providing MAC must be qualified to convert to general anesthesia when necessary and to rescue the patient’s airway in the event of complications.

Additional References:
Modified Observer’s Assessment of Alertness/Sedation Scale (MOAAS)
Ramsey Scale

Different levels of sedation may be needed for different patients undergoing the same procedure. Additionally, the same patient may require varying levels of sedation during a single procedure.  For example, a patient undergoing colonoscopy may experience greater pain and require more analgesia/sedation at points in the procedure when the colon wall is being stretched.

In prolonged or complex procedures or other selected circumstances, deeper levels of sedation including deep sedation and general anesthesia may need to be considered. Most general, diagnostic, and uncomplicated gastrointestinal endoscopic procedures, however, can be performed under moderate sedation. 

Targeting moderate sedation is generally considered a safe goal for non-anesthesiologists who have some training and experience in administering IV sedation. However, a critical point of understanding for the non-anesthesiologist is that although patient characteristics (see Patient Factors Involved in Choice of Sedation Regimen above) may help determine the target dosage, the exact dose needed to complete the procedure in a given patient is impossible to accurately predict. It is possible, for example, to see the blood concentration of a drug to be as much as five times different in two patients of the same weight who received the same dose.  In addition, even when the blood levels of a particular drug are similar, one patient’s experience of sedation can be quite different from that of another. Therefore, a successful outcome is dependent on an understanding of incremental dosing, the synergistic effects of drug classes, and the onset of action and peak effects of sedation agents.  In addition, clinicians should always be prepared to rescue patients who move to the next deeper level of sedation.

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American Society of Anesthesiologists. Distinguishing Monitored Anesthesia Care (“MAC”) from Moderate Sedation/Analgesia (Conscious Sedation). (Approved by the ASA House of Delegates on October 27, 2004) http://www.asahq.org/publicationsAndServices/standards/35.pdf  Accessed April 22, 2008.

American Society for Gastrointestinal Endoscopy. Guidelines for conscious sedation and monitoring during gastrointestinal endoscopy. Gastrointestinal Endoscopy. 2003;58(3):317-322.
http://www.asge.org/uploadedFiles/Publications_and_Products/Practice_Guidelines/2003_sedation.pdf Accessed August 24, 2009.

American Society For Gastrointestinal Endoscopy. Guidelines for the use of deep sedation and anesthesia for GI endoscopy. Gastrointestinal Endoscopy. 2002;65(5). http://www.asge.org/searchnew.aspx?searchtext=deep%20sedation

Cohen, LB et al. AGA Institute Review of Endoscopic Sedation, Gastronenterology 2007;133:675-701.

Drossman DA, Shaheen NJ, Grimm IS, eds. Handbook of Gastroenterologic Procedure, 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2005:14

Lightdale CJ, Lightdale JR. Advances in Endoscopy and Endoscopic Sedation. Medscape, 2003. http://www.medscape.com/viewarticle/456991  Accessed April 22, 2008.

Rex DK. Moderate Sedation for Endoscopy: Sedation Regimens for Non-Anesthesiologists, Ailment Pharmacol Ther. 2006;24(2):163-171
http://www.medscape.com/viewarticle/537718  Accessed February 13, 2008.

Van Dam J, Wong RCK. Handbook of Gastrointestinal Endoscopy, Georgetown,Texas: Landes Bioscience; 2004:3.

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Last Updated September 29, 2008