How Does Anesthesia Work?

Anaesthesia is one of the most important discoveries in medicine and healthcare. How does it work?

Table of Contents

Opium poppy, a common anaesthetic
Opium poppy, a common anaesthetic, Credit: Wikimedia/ Mark Nesbitt and Delwen Samuel

What is anesthesia?

Anesthesia is the use of medicines to prevent patients from feeling pain during surgeries and other medical procedures. The medicines used are known as anesthetics. The first surgical procedure using this method was done by William T.G. Morton In 1846. He was a dentist from Boston. He used sulfuric ether, a chemical compound, as an anesthetic on his patient. The surgery was a success, and soon large crowds gathered around his clinic to have their teeth pulled out without any pain.

William T. G. Morton
William T. G. Morton Credit: Wikimedia/Wellcome Images
Regional anaesthesia being given at the spine
Regional anesthesia being given at the spine, Credit: Wikimedia/ Paul Anthony Stewart

How does it work?

The way by which anaesthesia works has been studied for years, and is still not fully understood. So far, it is understood that anaesthetics target the central nervous system.


Our body feels pain by sending signals to the brain and central nervous system. Local anaesthetics block these signals, and that prevents the feeling of pain. They do this by binding to an ion channel called the sodium channel. This ion channel is found on the nerve cells. The sodium ions released from these channels are messengers between the central nervous system and the rest of the body. When this communication is shut off, the body does not feel pain.

Procaine is a local anaesthetic commonly used in dental procedures
Procaine is a local anaesthetic commonly used in dental procedures, Credit: Wikimedia/Techelf

General anesthetics put the patient to sleep. While they are unconscious they are still breathing and maintaining blood pressure . General anesthetics block communication with the central nervous system but act differently from local anaesthetics. They disrupt ion channels called potassium channels. General anaesthetics also act on the neurotransmitter , GABA . GABA is essential for passing messages from one nerve cell to another. This makes the patient pass out. How they do this is not fully understood yet.

Types of anesthesia

Anesthesia is of four types.


  • General anesthesia: General anesthesia causes the patient to lose consciousness. The patient does not feel any pain during the surgery, nor has any memory of the surgery afterwards. It is given continuously through an intravenous line, or by gas through a mask. A tube is inserted through the patient’s mouth, which helps the patient breathe while unconscious. The patient wakes up once the anesthetic is no longer being given. General anesthesia is used in major surgeries involving internal organs, like the liver, or transplants. This anesthesia works by numbing the brain so that it stops responding to pain signals.


  • Sedation: Sedation is a type of anesthesia in which the patient is half-awake, but not fully unconscious. This type of anesthesia is given to make the patient more comfortable before minor procedures like biopsies or root canals.


  • Local anesthesia: Local anesthesia is given for a short amount of time to stop the feeling of pain in a certain location on the body. The patient may be awake during the surgery. Local anesthesia can be given through an injection or absorbed through the skin. This is used in minor surgeries, such as filling a cavity in a tooth or removing a mole on the skin.


  • Regional anesthesia: Regional anesthesia numbs the part of the body undergoing surgery, for example, a leg. The anesthetic is injected at that part.
Halothane is a commonly used general anaesthetic
Halothane is a commonly used general anesthetic Credit: Wikimedia

Who performs anesthesia?

The doctors who perform surgery are usually not also in charge of anesthesia. Before the surgery, an anesthesiologist either injects the anesthetic or transfers it through an IV line. In other cases, the patient might have to breathe in an anesthetic gas. The patient should fall asleep within a couple of minutes.


The dosage is monitored and applied by an anesthesiologist. An anesthesiologist is a medical professional who has studied anesthetic procedures.

Benefits of anesthesia

Anesthesia has many benefits. It has helped medicine and healthcare progress at a very high rate. The major benefit of anaesthesia is that it reduces pain during surgeries. When the patient does not feel pain, the doctor can work more carefully and thoroughly. Many parts of the body can be looked at more closely and understood more thoroughly.

Doctors performing complex surgeries thanks to anaesthesia
Doctors performing complex surgeries thanks to anaesthesia Credit: Wikimedia/Pfree2014

Surgery is very stressful for a patient, and stress makes the body react negatively. When a patient is calm during surgery, it goes smoothly and there are fewer risks. Calmness comes from relaxed breathing and normal blood pressure. When the breathing is abnormal and the blood pressure is high,  hormones are released that cause additional distress. Anaesthesia rules out all these risks by making sure the patient is relaxed.


Anaesthesia is especially helpful during emergencies. In situations where a patient needs surgery urgently, anaesthesia can be given easily. It does not take a long time to show its effects. Anaesthesia can also be given for a longer time without risks. So, if the surgery is long, the patient can stay under for as long as required. The effects can be easily reversed once the surgery is over.


Anesthesia is one of the most important scientific discoveries. It is used in many medical procedures. It has very few risks and is one of the safest medical procedures. It has helped save millions of lives.


Science has come a long way, from using plant chemicals as painkillers to manufacturing chemicals that prevent pain during surgery. There is a lot to learn about anaesthesia, but we hope to understand it better in the coming years.


Biopsy: The procedure of removing a small amount of tissue or cells for diagnosis of disease


Blood pressure: The pressure with which blood flows through arteries


GABA: Gamma-aminobutyric acid


Hormones: The body’s chemical messengers


Ion channels: Protein molecules found on cell membranes that help in the movement of ions


Neurotransmitters: Molecules that pass on signals from one nerve cell to the other

Flesch Kincaid Grade Level: 8


Flesch Kincaid Reading Ease: 58.6

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  • Sanjana Kadur
    : Author
    Sanjana is doing her masters in biochemistry. She loves all things biology and truly believes that dogs make the world a better place. She enjoys playing basketball and spends most of her evenings on the court. Writing for Smore Science gives her the creative freedom to write about science in a fun and relatable way.

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