Anesthesia is a type of medication that prevents people from feeling pain during or following surgery. There are four main categories of anesthesia: local, regional, general, and sedation.

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The type of anesthetic a person receives may vary according to the kind of medical procedure they require and their individual health needs.

This article describes what anesthesia is, outlines the four types of anesthesia, including their uses and side effects, and provides information on the safety of anesthesia.

The term anesthesia translates to “loss of sensation.” It is a state that involves a temporary loss of pain or awareness. Medical professionals administer anesthesia so that people do not feel pain during medical procedures.

Doctors use anesthetic drugs to induce anesthesia. There are four main types of anesthetic: general, local, regional, and sedative.

  • General anesthetics put a person into a state of controlled unconsciousness so that they do not experience pain during the procedure and do not know what is happening.
  • Local and regional anesthetics numb the part of the body that requires numbing, allowing the patient to stay awake during the procedure.

Doctors may administer anesthetics via the following, depending on the type of anesthetic and the type of medical procedure:

  • injection
  • inhalation
  • topical application

Until recently, experts knew very little about how anesthetics worked. Most experts now agree that the drugs work by targeting proteins in the membranes surrounding nerve cells. Since intravenous anesthetics produce different effects to inhaled anesthetics, scientists suspect that the two types of drugs target different sets of proteins.

Doctors use local anesthesia to numb a specific area of the body. Although a person cannot feel pain after receiving a local anesthetic, they may still feel some pressure or movement. Unlike general anesthetics, local anesthetics do not cause a person to lose consciousness.

What is it for?

Local anesthetics stop the nerves in a part of a person’s body from sending pain signals to their brain. This prevents the person from feeling pain.

Medical professionals may administer local anesthetics for a variety of reasons, including:

  • Treating pain: A person can take over-the-counter (OTC) sprays and gels that contain a local anesthetic for mild conditions, such as sore throats and mouth ulcers. A doctor may administer an injection of local anesthetic and steroid medication for more serious conditions, such as joint pain.
  • Minor procedures: A doctor may give an anesthesia injection alongside a sedative to help keep a person relaxed and pain-free during a procedure. Health professionals typically use local anesthetics for minor procedures, such as:
  • Major procedures: Occasionally, doctors may use local anesthesia during major surgeries where the person needs to be awake, such as during some types of brain surgery. They may also provide local anesthesia to prevent pain following major surgery.

What does it involve?

Certain medications containing local anesthetic are available OTC or via prescription. Depending on their intended use, local anesthetics are available as:

  • creams, gels, or ointments
  • sprays
  • lozenges
  • injections

How long does it last?

Local anesthesia usually causes numbness within a few minutes. A person should regain full feeling a few hours later, as the medication wears off naturally.

Side effects

Local anesthetics are generally safe. Nonetheless, a person may experience mild side effects. Depending on the method of delivery, these side effects may include:

In rare cases, a person may have an allergic reaction to the anesthesia. This could result in seizures or cardiac arrest.

Regional anesthesia is similar to local anesthesia in that it causes localized numbness. However, doctors may use regional anesthesia to numb a larger area, such as the entire body from the waist down.

What is it for?

Doctors often use regional anesthesia in the form of epidurals or spinal blocks. Both types of anesthesia involve injecting an anesthetic into the spine to block pain signals traveling back to the brain.

  • Epidural: An epidural is the most common form of pain control that doctors use during labor and delivery. This allows the person giving birth to feel less pain and remain awake to push when it is time to deliver the baby.
  • Spinal block: A spinal block is stronger than an epidural and provides more immediate pain relief. Doctors typically use spinal blocks during cesarean deliveries.

What does it involve?

A doctor may inject a regional anesthetic near a particular nerve cluster to prevent pain signals traveling through that nerve cluster to the brain. The person receiving the anesthesia may remain awake, or the doctor may give them a sedative.

For an epidural or spinal block, the doctor injects anesthetic medication into or near the spinal canal, which interrupts sensation from the legs or abdomen. A doctor can also perform blocks on the other limbs or extremities.

A person will receive an epidural or spinal block injection while lying down or sitting up. Before the doctor injects the regional anesthetic, they will use a local anesthetic to numb the back area.

How long does it last?

A single injection of a regional anesthetic can cause numbness for 4-24 hours, depending on the regional anesthetic used.

Side effects

Regional anesthesia can cause the same side effects as local anesthesia. When a doctor inserts a needle or catheter under the skin, a person may experience bleeding, infection, or bruising.

Weakness and numbness may last for a short period after the medication has worn off.

Medical professionals use general anesthesia to induce a state of controlled unconsciousness. This ensures that the person undergoing the operation is unaware of the surgery, does not feel pain, and does not move during the procedure.

What is it for?

Doctors use general anesthesia for surgical procedures when it is safer and more comfortable for the person to be unconscious.

What does it involve?

Doctors administer general anesthesia as a gas that the person inhales through a mask or a liquid that the person receives directly into a vein.

General anesthesia typically takes effect very quickly. A person will generally feel lightheaded before becoming unconscious within about a minute.

An anesthetist will remain with the person throughout the surgery to ensure that they remain unconscious. They will also provide medication to prevent pain when the person wakes up after the surgery.

How long does it last?

Once the surgery is complete, the anesthetist will stop providing the anesthesia. This causes the person to wake up gradually.

Some people may have to remain in the hospital for a few hours to a few days. General anesthesia can affect a person’s memory, reflexes, and concentration for a day or two.

Side effects

There are some common side effects associated with general anesthesia. These include:

Doctors use sedation to relax a person. This can sometimes result in the person becoming drowsy or sleepy. Other terms for sedation include:

  • twilight sedation
  • conscious sedation
  • monitored anesthesia care

What is it for?

Doctors typically use sedation for minor surgeries or for short, uncomplicated procedures where a local anesthetic is insufficient, but the procedure does not require a general anesthetic.

What does it involve?

Doctors usually provide sedation and painkillers intravenously. The level of sedation may range from minimal, where a person feels drowsy but can still talk, to deep, where the person probably will not remember the procedure.

Doctors may sometimes provide oxygen, as sedation can slow breathing.

Unlike general anesthesia, sedation does not cause unconsciousness.

How long does it last?

People typically wake up very soon after the procedure, once the anesthetist stops administering the sedative.

Side effects

Compared to general anesthesia, sedation is associated with fewer side effects, and a person will likely recover more quickly and go home sooner. Some possible side effects include:

  • drowsiness
  • nausea
  • headache

Experts generally consider anesthesia very safe, owing to advances in training, medication, and equipment. Serious problems are rare for people who undergo anesthesia. However, there are potential complications. These include:

  • Allergic reaction: about 1 in 10,000 people experience serious, life-threatening allergic reactions to anesthetic. More than 95% of these people survive and recover well. Treatment is on hand during surgery to effectively handle this occurrence.
  • Delirium: Some people may experience confusion following anesthesia. People over the age of 60 may experience delirium for several days following surgery.
  • Awareness during surgery: Although rare, a person may hear sounds and feel pain while they are supposed to be unconscious under general anesthesia.
  • Death: Around 1 in 100,000 people who are healthy and receiving non-emergency surgery die under general anesthesia.

Anesthesia refers to a group of medications that doctors use to prevent pain during surgery or procedures. There are four main types of anesthesia: local, regional, general, and sedation.

General anesthesia induces a state of controlled unconsciousness in which a person cannot feel pain and has no awareness of the procedure. Local and general anesthetics prevent pain without inducing a state of unconsciousness.

Sedation relaxes a person, and doctors usually combine it with analgesics to calm and keep the person free of pain. Doctors may choose this option when a local anesthetic would not suffice, but general anesthesia is unnecessary.

Anesthesia is generally safe, and complications are rare but possible. Depending on the type of anesthesia used, these complications may include allergic reactions, permanent nerve damage, and, rarely, death.