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Why twilight sleep?



For a routine colonoscopy, my doctor is letting me decide between twilight and total anesthesia. But she says that total anesthesia is safer (anesthesiologist present) and has fewer after effects. I forgot to ask her why, in that case, any one doctor offers twilight sleep or any patient chooses it. What are the tradeoffs?


Twilight anesthesia and total anesthesia are not standard terms, so I can't really tell you exactly what your doctor means. The official classification of "levels of sedation" goes as follows:

1. Minimal sedation (anxiolysis) is a drug-induced state during which patients respond normally to verbal commands.

2. Moderate sedation/analgesia (conscious sedation) is a drug-induced depression of consciousness during which patients respond purposefully to verbal commands, either alone or accompanied by light tactile stimulation.

3. Deep sedation/analgesia is a drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulation.

4. Anesthesia consists of general anesthesia and spinal or major regional anesthesia. It does not include local anesthesia. General anesthesia is a drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation.

 My guess is that your doctor is offering you either a Level 1-2 experience in which you are given small amounts of intravenous sedation, administered by a nurse, or a Level 3-4 experience involving an anesthesiologist. With the latter you have the benefit of greater comfort for you during the procedure, and possibly better conditions for the doctor doing the colonoscopy. This usually comes at a higher cost, (although you may not be the one paying) but with perhaps a slightly longer recovery time. An intravenous infusion of a drug called propofol is very often used for deeper sedation, however propofol is not the only drug that can be used for this.

The key question is safety. There is probably no significant difference between the two approaches as far as safety (the risk of harm) is concerned, assuming you've got competent professionals doing the work. Anyone permitted to administer lower levels of sedation must have the ability to "rescue" the patient from deeper levels that may occur unintentionally. In the United States anyone providing general anesthesia or deep sedation is likely to be an anesthesiologist or nurse anesthetist, although some gastroenterologists are seeking special permission, through legislation, to allow them to administer propofol for colonoscopies without an anesthesia provider.

For more information:

Go to the Anesthesia health topic, where you can:

Response by:

Gareth S Kantor, MD Gareth S Kantor, MD
Assistant Professor of Anesthesiology
School of Medicine
Case Western Reserve University