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Knocked Out, Put Under, Anesthetized and Sedated: Different Types of Anesthesia

Whether you call it being "put under" or "knocked out", anesthesia conjures up mental images of deeply sedated patients unable to speak, move or even breathe on their own. However, not all kinds of anesthesia are made equal, and not all kinds carry the same risks.

If you’ve read the article I wrote about why patients are allowed to drink clear fluids but not eat before surgery you’ll know that I recently had surgery to repair the ACL and meniscus in my left knee. I was given instructions to stop eating at midnight the evening before surgery so that my stomach would be empty come the morning. This was to reduce the risk that I would regurgitate food from my stomach into my trachea and choke once I was “put to sleep”. However, as it turns out, because I was not put under general anesthesia for my surgery, the risks that I would aspirate were negligible. What did I have, if not general anesthesia? Let me explain.

There are four main categories of anesthesia: general, regional, sedation and local.

General anesthesia is likely what you’re thinking of when you picture surgical anesthesia. It is technically a medically induced coma, with the drugs being administered through an IV or a mask. During general anesthesia, you usually require some form of a breathing tube, as spontaneous breathing often does not occur. Because your breathing reflexes, like coughing, are inhibited, you’re at an increased risk of aspiration. It takes about an hour to wake up from this type of anesthesia once the drugs stop being delivered to your bloodstream.

Regional anesthesia is commonly used for cesarean sections and orthopedic surgeries. It involves injecting local anesthetic into the nerves that provide sensation to a part of the body but leaves you fully conscious. Commonly the injections are done in the spine (like with an epidural) or near the top of a limb (like with a femoral block) and take hours to wear off. This type of anesthesia is often combined with the next type, sedation.

Sedation, often referred to as “twilight sedation”, involves administering drugs that make a patient sleepy, relaxed and unfocused. While you are not forced unconscious like with general anesthesia, you may naturally fall asleep due to drowsiness. Sedation does not inhibit your breathing or reflexes and thus doesn’t carry the aspiration risks general anesthesia does. It wears off fairly quickly and thus allows recovery times to be faster.

Local anesthesia is what you get at the dentist. It involves administering a small amount of a drug like lidocaine to a specific area, usually via injection. Beyond dental fillings, it can be used for simple procedures like stitching up a cut. Local anesthetics may also be injected after surgery to help a patient avoid feeling pain as they wake up.

I was given a femoral block (or an injection of anesthetic directly into my femur) so that my entire leg from the thigh down was numb for over 12 hours. I was also given a spinal injection so that everything below my waist was numb for quite a while, and some sedatives, so that I was able to doze through the procedure. Interestingly, the surgeon knew I was interested in science, so offered to show me some of the procedure with the laparoscopic camera! I’m told I was very engaged and asking questions about what he was doing. Unfortunately, either due to the sedation or my own history of sleepwalking and talking, I don’t remember any of it!


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