How Anesthesia Works

Procedural Sedation, the Twilight Sleep

You may have undergone procedural sedation and not realized that it even qualified as anesthesia. If you've had your wisdom teeth taken out, for example, you've probably had procedural sedation. This type of anesthesia is used for short, relatively minor medical procedures and is also known as conscious sedation or twilight anesthesia. In addition to dental work, procedural sedation is used for things like setting broken bones, LASIK and minor cosmetic surgeries.

Under procedural sedation, you remain fully awake and can respond to questions and instructions. That doesn't necessarily mean that you know what's going on, though -- you'll be sleepy and relaxed. You typically won't remember the procedure or the short period of time following it. Some of the drugs used in procedural sedation can make you feel giddy or euphoric.


Procedural sedation has a lot in common with general anesthesia. That's because the same types of drugs used in general anesthesia are also administered in procedural sedation; they're just given in much smaller amounts. Usually, this means a sedative such as ketamine or nitrous oxide, which depresses the central nervous system. Sometimes a dissociative, which keeps nerve sensations from reaching the brain, is used instead, such as diazepam (more commonly known as Valium) or midazolam.

In high doses, these drugs induce sleep and paralysis and affect the cardiovascular system, but in lower doses, they calm the patient and reduce anxiety. For procedural sedation, one of these types of drugs is used in combination with an analgesic such as fentanyl for pain relief. These anesthetics may be inhaled, given orally, injected or used in a combination of the three methods. For example, nitrous oxide and other sedative gases are inhaled, but ketamine and Valium are injected into an IV line.

How long the procedural sedation lasts depends on the drugs administered -- it may be as few as five or 10 minutes or as long as an hour. Recovery is speedy, and you won't usually have the side effects associated with general anesthesia, such as vomiting, nausea or dizziness (although they can still occur). Patients under conscious sedation still have to be carefully monitored to ensure that they don't slip into deeper sedation.

We'll look at another type of anesthesia next -- the local kind.