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An anesthetic is a drug that causes anesthesia, which is the loss of some or all feeling or awareness. Anesthetics are a safe and effective way to manage pain and keep someone calm during surgery or other painful tests or treatments.

Types of anesthesia

There are 3 types of anesthesia. The type and amount of anesthetic you are given depends on your age, weight, the type of test or procedure, the area of the body where the test or procedure will be done, any allergies you have, previous experience with anesthesia and your overall health.

Local anesthesia causes numbness or a temporary loss of feeling in one small area of the body, such as your elbow or one toe. You stay awake during the procedure but have no feeling in the part of the body treated with the anesthetic. A local anesthetic can be given as an injection, a spray or a cream. Local anesthetics may be used to numb the skin before a needle or surgical cut (incision).

Regional anesthesia causes numbness or a temporary loss of feeling in one large area of the body. Regional anesthetics are injected near a cluster of nerves to numb an entire part of the body, such as an arm or leg. On their own, regional anesthetics do not cause a loss of consciousness. In some cases, you may also be given other medicines that make you lose consciousness or change how awake you feel during the procedure.

Neuraxial anesthesia is a specific type of regional anesthesia where the anesthestic is injected into the area around the spine. It numbs an even larger part of the body, usually your entire body below your waist. An epidural and a spinal are examples of neuraxial anesthesia.

General anesthesia causes a loss of consciousness. It may be described as being asleep. But unlike regular sleep, you will not wake up during the procedure. While under general anesthesia, you do not feel the procedure or pain, are not aware of the procedure and will not remember the procedure after you wake up. A general anesthetic is given through a needle into a vein (intravenously or IV) or by breathing it in (inhalation).

Having general anesthesia

General anesthetics are given by an anesthesiologist. This is a doctor who specializes in giving anesthetics.

During inhalation anesthesia, the anesthesiologist holds a plastic mask over your nose and mouth and you breathe in the anesthetic medicine. The mask is attached to a machine that delivers oxygen and the anesthetic drug as a gas.

During IV anesthesia, the anesthetic medicine goes directly into your bloodstream through an IV line. A small IV needle is inserted in your hand or arm and anesthetic medicine is given through it. If you already have an IV in place (for example, to receive IV fluids during a hospital stay), this will be used to give you the anesthetic.

During your procedure, the anesthesiologist will also monitor your heart rate and rhythm, temperature, breathing, blood pressure and the amount of oxygen in your blood. To help you breathe while you are under the anesthetic, you will have oxygen delivered either through a tube (cannula) in your nose or a breathing tube placed into your throat through your mouth.

Preparing for anesthesia

Before having local anesthesia, you probably won't need to do anything to prepare.

Before regional or general anesthesia, you usually need to prepare. Your healthcare team will give you specific instructions about what to do or not do. You will need to stop eating and drinking a certain number of hours before your procedure and you may be told not to take certain medicines for a period of time.

Many people find it helpful to have a friend or family member go with them to the procedure. It is often necessary to have someone drive you home after a procedure that has involved an anesthetic. Ask your doctor what you should expect and plan for.

Side effects

After anesthesia, the healthcare team monitors you closely for possible side effects. Most side effects of anesthesia will go away as the anesthetic wears off. Some side effects may last longer, although they typically go away within a few hours or days.

Some side effects of general anesthesia include:

  • fatigue

  • dizziness

  • headache

  • irritability, disorientation and confusion

  • sore throat

  • dry mouth

  • cough

  • nausea

  • vomiting

  • chills or shaking

  • pain, tenderness, redness, or bruising at the spot where the IV was

  • difficulty urinating (peeing)

Side effects of local and regional anesthetics may include:

  • dizziness

  • headache
  • pain, tenderness, redness or bruising at the spot where the anesthetic was injected
  • muscle weakness
  • itching or tingling
  • difficulty urinating or incontinence (primarily following neuraxial anesthesia)

Serious side effects of general anesthesia such as an allergic reaction, brain injury or cardiac arrest are very rare, but they are possible. Serious side effects of regional anesthesia such as infection, nerve damage or bleeding around the spinal cord are also rare but possible. Your healthcare team is trained to deal with these problems if they happen.

Special considerations for children

Preparing a child for anesthesia can help lower their anxiety, make them more cooperative and help them develop coping skills. Parents and caregivers can help prepare children by explaining to them what will happen, including what they will see, smell, feel, hear or taste during anesthesia.

A child’s age and development can affect their fears about anesthesia. Most kids are concerned about getting a needle. Sometimes, a local anesthetic can be applied as a cream to numb the skin before an injection or incision. Depending on the type of procedure, children may be given medicine to help them relax and feel sleepy before going into the operating room where the anesthetic is given. Children are also often given an inhaled anesthetic before any IV is placed.

Younger kids may be afraid of being separated from their parents, so it may help if you can be with them in the room until they fall asleep under general anesthesia. If you child has a favourite stuffed animal, toy or blanket, it may also help them to bring this along for comfort if possible. Talk to your child's anesthesiologist about what might be possible.

Older children may be afraid of pain, cutting or scarring of the body or waking up during surgery.

To help prepare children for general anesthesia:

  • Let your child know where you will be during the surgery or test. For example, you will be nearby in the waiting room or in the recovery room when they wake up.
  • Explain to them in a way they can understand that the doctor will give them medicine to make them nap or sleep so that they won’t feel anything during the test or surgery.
  • Reassure your child that they will not wake up during the surgery or test. They will wake up after.
  • Explain that they may feel a little weird after surgery and that is normal. They may have some pain after the surgery, but the doctor will give them medicine to help.
  • Try to create a calm, supportive and soothing environment for your child before and after the surgery or test.
Preparing a child for general anesthesia depends on the age and experience of the child. Find out more about helping your child cope with tests and treatments.

Expert review and references

  • Layla Baghirzada, MD, FRCPC, MPH

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