# Anaesthesia > Surgery without pain or awareness - Date: 1846 - Era: Industrial age - Domain: [Medicine & Hygiene](https://lastcodex.org/en/domains/medicine/) - Rebuild stage: IV (Science & industry) - Difficulty: 4/5 - URL: https://lastcodex.org/en/inventions/anaesthesia/ Anaesthesia is the medical practice of taking away pain, and often awareness, so that an operation can be done. Since a public demonstration with ether in Boston in 1846, trained anaesthetists, monitoring and oxygen have made it routine, and together with antisepsis it turned surgery from a last resort into ordinary care. ![Anaesthesia · Surgery without pain or awareness](https://lastcodex.org/_astro/plate.CZq0JV73_WgXEw.webp) ## Legend 1. Glass globe of Morton's ether inhaler 2. Mouthpiece and valve 3. Gas cylinders 4. Glass flowmeters 5. Vaporiser bottle 6. Reservoir bag and face mask ## What it is Anaesthesia removes pain, and in its general form awareness as well, so that a surgeon can operate. General anaesthesia is a controlled, reversible unconsciousness. Regional anaesthesia numbs a large part of the body, such as a limb or everything below the waist, while the patient stays awake. Local anaesthesia numbs a small area, enough to stitch a cut or treat a tooth. The plate sets two machines side by side. On the left is the glass inhaler with which William Morton gave ether in Boston in 1846. On the right is an anaesthetic machine of the early twentieth century: cylinders of compressed gas, glass flowmeters, a bottle where the gas picks up the vapour of a volatile agent, and a bag and mask through which the patient breathes. ## How it works General anaesthetics reach the brain through the blood, breathed in through the lungs or injected into a vein. Many of them strengthen the effect of GABA, the brain's main braking signal, so that nerve cells fire less. Consciousness fades and no memories are laid down. The details are still debated. Depending on the drug and the patient, the depression also reaches the centres that keep the body running. Breathing can become shallow or stop. The throat muscles relax, so the tongue can fall back and block the airway. Coughing and swallowing reflexes weaken, and stomach contents can rise into the lungs. Blood pressure often drops. The anaesthetist therefore keeps the airway open, gives oxygen, often breathes for the patient through a tube or mask, and adjusts the drugs minute by minute. ![A peripheral nerve cut across, showing bundles of fibres in their sheaths](https://lastcodex.org/_astro/v1.BC0uAuQx_Z25hngS.webp) _A nerve is a cable of thousands of fibres; a local anaesthetic silences each one it reaches._ Local anaesthetics act on the nerves themselves. A nerve signal is a wave of electrical change running along a fibre, carried by sodium ions rushing in through tiny channels in its membrane. The drug blocks these channels, so the wave dies where the drug lies and the brain hears nothing from beyond it. Placed around a nerve, it numbs whatever that nerve supplies; in the fluid around the spinal nerve roots, it numbs the lower half of the body. Heart and brain cells use the same kind of channel, so too much local anaesthetic in the blood can cause fits or stop the heart. ## How it is made safe This section describes how hospitals organise anaesthesia, not a procedure to follow outside them. **A trained team.** Depending on the country, the anaesthetic is given by a doctor trained in it for years or by specialist nurses. They stay with the patient from the first drug until breathing and consciousness are safely back. **Assessment beforehand.** The team asks about illnesses, medicines, allergies and earlier anaesthetics, examines the mouth, neck, heart and lungs, and chooses with the patient between general, regional and local anaesthesia. **An empty stomach.** Before a planned operation, patients stop eating some hours ahead, often about six after a light meal, which lowers the risk of stomach contents reaching the lungs. The hospital sets the exact times for each patient. **Equipment checked before each case.** Oxygen with a reserve cylinder, suction, devices to hold the airway open, a way to ventilate by hand if the machine fails, and resuscitation drugs. A field hospital uses simpler equipment, but cannot leave any of these out. ![A pulse oximeter clipped to a fingertip, with red light passing through it](https://lastcodex.org/_astro/v2.Bw1UplRP_10vbPA.webp) _The probe shines red and infrared light through the finger and estimates what share of the haemoglobin is carrying oxygen._ **Monitoring throughout.** A pulse oximeter shows the oxygen saturation of the blood. Other instruments track heart rhythm, blood pressure and the carbon dioxide in each breath out, which shows that air is really reaching the lungs. None of them replaces an anaesthetist watching the patient. **The checklist.** In 2008 the World Health Organization introduced a surgical safety checklist. The team pauses before the anaesthetic, to confirm the patient, the operation, allergies, a difficult airway and a working pulse oximeter, then again before the incision and before the patient leaves the theatre. In a study of eight hospitals, deaths after major surgery fell from 1.5% to 0.8%. **Recovery.** Patients wake in a recovery room where nurses watch breathing, oxygen, pain and nausea. After a general anaesthetic, someone must take them home, and they should not drive for at least a day. > **Safety.** Anaesthetic gases and drugs must never be used outside trained medical care. With many of these drugs, the dose that removes awareness is not far from one that stops breathing or abolishes the protective reflexes, and the gap varies between people and from minute to minute. Without someone trained to keep the airway open and give oxygen, and without monitoring and resuscitation equipment, an unconscious person can die within minutes. Breathing gases or solvents for their effect has killed many people, and ether is highly flammable. A person in severe pain or needing an operation should be taken to a hospital. ## History and evolution Before anaesthesia, surgeons relied on alcohol, opium and speed. On 13 October 1804, in Japan, Hanaoka Seishū removed a breast tumour from a woman who had swallowed his herbal mixture, but Japan was closed to the world and his work stayed unknown abroad. In 1800 Humphry Davy suggested that nitrous oxide might be used in surgery. In December 1844 the dentist Horace Wells had a tooth pulled under the gas, but his demonstration in Boston in January 1845 failed when the patient cried out. In Georgia, Crawford Long had operated under ether on 30 March 1842, but published only in 1849. ![An empty nineteenth-century surgical amphitheatre with tiered wooden rows under a domed skylight](https://lastcodex.org/_astro/v3.39NIJtIs_naaiU.webp) _Surgery was taught in steep amphitheatres like the one in Boston now called the Ether Dome._ The plate takes 16 October 1846 as its date. At Massachusetts General Hospital, Morton gave ether to Gilbert Abbott while the surgeon John Collins Warren removed a tumour from his neck. The news spread fast, and within months ether was in use in Europe. In Edinburgh, James Young Simpson tried chloroform on 4 November 1847; it acted faster and did not burn, but the margin between enough and too much was narrow. John Snow studied its doses and in 1853 gave it to Queen Victoria for the birth of Prince Leopold. Anaesthesia allowed longer operations, but wounds still festered until antisepsis arrived in the late 1860s. In 1884 Carl Koller showed that cocaine numbed the eye, and in 1898 August Bier gave the first spinal anaesthetic in Kiel. Cocaine was toxic and addictive, so safer synthetic drugs followed: procaine in 1905, lidocaine in the 1940s. In the twentieth century intravenous drugs and muscle relaxants arrived and breathing tubes came into routine use, and pulse oximetry, described by Takuo Aoyagi in 1974, spread through operating theatres in the 1980s. ## Key figures - Ether Day: 16 October 1846, Massachusetts General Hospital, Boston - Hanaoka's operation: 13 October 1804, Japan, under an anaesthetic taken by mouth - Cocaine on the eye: Koller's paper read at Heidelberg on 15 September 1884 - Pulse oximetry: Principle described by Takuo Aoyagi in 1974 - WHO surgical safety checklist: 19 items; in eight trial hospitals deaths fell from 1.5% to 0.8% (2009) ## Requires - [Hygiene & Antisepsis](https://lastcodex.org/en/inventions/antisepsis/): Stopping the spread of germs (1847) - [Glass](https://lastcodex.org/en/inventions/glass/): Melted sand you can see through (c. 2,500 BCE) ## Sources - [Ether & Ether Dome History](https://libguides.massgeneral.org/mghhistory/ether), Massachusetts General Hospital, Treadwell Virtual Library - [Crawford Long (Scientist of the Day)](https://www.lindahall.org/about/news/scientist-of-the-day/crawford-long), Linda Hall Library - [The surprising and long story of the first use of ether in surgery](https://theconversation.com/the-surprising-and-long-story-of-the-first-use-of-ether-in-surgery-113340), The Conversation - [Horace Wells (1815–1848) and William TG Morton (1819–1868): pioneers in anaesthesiology](https://scielo.org.za/pdf/sadj/v75n2/11.pdf), South African Dental Journal, vol. 75 no. 2 (2020) - [Davy, Researches, chemical and philosophical, chiefly concerning nitrous oxide (1800)](https://heirs.lib.uiowa.edu/record.php?id=1338.5), Heirs of Hippocrates, University of Iowa Libraries - [History of the Japanese Society of Anesthesiologists](https://anesth.or.jp/users/english/about_jsa/history), Japanese Society of Anesthesiologists - [A great leap forward: James Young Simpson](https://archiveandlibrary.rcsed.ac.uk/special-collections/the-battle-for-midwifery/a-great-leap-forward-james-young-simpson), Royal College of Surgeons of Edinburgh - [John Snow: anesthesia](https://epi-snow.ph.ucla.edu/Stream4_Snowlife_d.html), UCLA Fielding School of Public Health - [Cocaine: what is the crack? A brief history of the use of cocaine as an anesthetic](https://pmc.ncbi.nlm.nih.gov/articles/PMC4335732/), PubMed Central - [Cocaine and self-experimentation](https://anaesthetists.org/Home/Heritage-centre/Learning/Heritage-Centre-blog-celebrating-75-years-of-Anaesthesia/Cocaine-and-Self-experimentation-a-blog-post-from-the-Heritage-Centre), Association of Anaesthetists, Heritage Centre - [Sodium channels and local anesthetics: old friends with new perspectives (Körner et al., 2022)](https://www.frontiersin.org/articles/10.3389/fphar.2022.837088/full), Frontiers in Pharmacology - [How general anesthetics work (Hibbs lab, Nature 2020)](https://www.utsouthwestern.edu/ctplus/stories/2020/general-anesthetics-benzos.html), UT Southwestern Medical Center - [General anaesthesia](https://www.nhs.uk/conditions/general-anaesthesia/), NHS - [Local anaesthesia](https://www.nhs.uk/conditions/local-anaesthesia/), NHS - [Pulse oximetry, Takuo Aoyagi memorial issue (Journal of Anesthesia, 2021)](https://pmc.ncbi.nlm.nih.gov/articles/PMC8327306/), PubMed Central - [Safe surgery: tools and resources](https://www.who.int/teams/integrated-health-services/patient-safety/research/safe-surgery/tool-and-resources), World Health Organization - [RCSI endorses the World Health Organisation's second Global Patient Safety Challenge (June 2008)](https://www.rcsi.com/dublin/news-and-events/news/news-article/2008/06/rcsi-endorses-the-world-health-organisations-second-global-patient-safety-challenge), RCSI University of Medicine and Health Sciences - [Implementation manual: WHO surgical safety checklist 2009](https://www.who.int/publications/i/item/9789241598590), World Health Organization - [Simple surgical checklist cuts deaths 40 percent](https://hms.harvard.edu/news/simple-surgical-checklist-cuts-deaths-40-percent), Harvard Medical School Fact-checked on 2026-10-14. --- The Last Codex · https://lastcodex.org/en/inventions/anaesthesia/ · © The Last Codex. 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