Anesthesia: Stages, Side Effects & Risks

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Anesthesia is medicine used to control a person's consciousness or pain perception during surgery or another medical procedure. This lesson will explain the different types of anesthesia, the side effects, and the risks involved.

What Is Anesthesia?

I had my appendix removed when I was a kid, and I had to be unconscious during the surgery. The doctor gave me some medicine that allowed me to 'sleep' my way through the procedure without feeling the pain of the incision or appendix removal. This medicine is called anesthesia.

Anesthesia can refer to a variety of medicine used to subdue a patient during a medical procedure. The type of anesthesia used depends on what function it's intended to have. For example, there are five general uses:

  1. to block pain
  2. to keep someone from moving
  3. to induce amnesia (memory loss)
  4. to weaken the body's autonomic response to a stimulus
  5. to make someone unconscious.

When anesthesia is administered to a patient, the dose and the patient's response is closely monitored by an anesthesiologist, a doctor who specializes in anesthesia.

An anesthesiologist specializes in the use of anesthesia.

Types of Anesthesia

There are different types of anesthesia based on the type of procedure being performed and the amount of body affected. Let's take a look at the three basic types.

  • Local anesthesia: this numbs an isolated part of the body while the patient usually remains awake and alert. For example, a dentist might numb half of your mouth when you have a cavity filled. It isn't necessary to render you unconscious (though some of us might prefer that over being awake with someone digging in your mouth), but it's enough to limit the amount of pain you feel during the procedure.
  • Regional anesthesia: this numbs a larger portion of the body than local anesthesia does. It may be administered with another medication to help you relax or sleep. One example of regional anesthesia you may have heard of is an epidural, which many women have during birth to reduce the pain involved, especially if it's a long labor.
  • General anesthesia: this type affects the entire body and results in the person being unconscious and the brain is unresponsive to reflex response or pain signals. It can be administered through inhalation or intravenously (commonly called an IV) and is commonly used in major surgeries like organ transplants or other internal repair or alteration.

Stages of General Anesthesia

General anesthesia affects the entire body, so there are different stages a person goes through.

Stage 1 - the patient is given the anesthesia and they fall asleep; however, they can still feel pain at this point.

Stage 2 - the patient enters what's called the REM stage. A person isn't kept in this stage very long because they can be prone to involuntary movements and vomiting (neither of which are good if you're about to have surgery).

Stage 3 - where a patient is kept for the duration of the procedure. At this point they are still, breathe regularly, and have a steady heart rate.

Stage 4 - most patients never experience this stage, which is good, because this stage signals an overdose. Blood pressure plummets and circulation can stop completely, killing the patient. An anesthesiologist is trained to monitor a patient's vital signs to keep them in stage 3 and avoid an overdose leading to stage 4.

Once the procedure is completed, the anesthesiologist will adjust the medication to slowly bring the patient back to consciousness.

Side Effects and Risks

Local and Regional Anesthesia

Local and regional anesthesia can have some lingering side effects after the procedure is finished. For example, the patient may feel numbness or have limited muscle control while the anesthesia wears off. They may also feel chilled or cold.

If a dose of local anesthesia is too high, it can unintentionally travel to another part of the body and affect a non-target area. When choosing an anesthesia, an anesthesiologist will consider a patient's medical history.

General Anesthesia

General anesthesia carries the most serious risks. Typically, a patient will be instructed to avoid eating or drinking anything for a period of time leading up to surgery. If you recall, vomiting is common during stage 2, so an empty stomach reduces the likelihood of anything coming up. It's also common for a person to feel nauseated once they wake up after the surgery, and this feeling may last a few days.

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