110 Fun Facts About Anesthesia

What are the three broad categories of anesthesia?

General, sedation and regional or local differ in how much of you is switched off. Under regional anesthesia a woman can stay awake through childbirth, while sedation can run from drowsy but talking to deep.

What are the three basic goals or endpoints of anesthesia?

Hypnosis, analgesia and muscle relaxation are produced by drugs acting on different parts of the nervous system, which is why an anesthetist usually combines several agents instead of relying on one.

Roughly what proportion of patients become aware during surgery under general anesthesia?

1 or 2 in 1,000 is the usual estimate, and most of those patients feel no pain. It is likeliest in emergencies such as urgent caesareans and trauma surgery, where a full dose of anesthetic would be unsafe.

About one patient in five reports having done what under general anesthesia?

Dreamed, said 22% of patients in one careful study, and the dreams were mostly pleasant and nothing to do with surgery. They were no sign of too light a dose: they seem to come as the drugs wear off.

The potency of an inhaled anesthetic correlates with its solubility in what?

Oil: around 1900 Meyer and Overton found that the more readily an anesthetic dissolves in olive oil, the more potent it is. For decades that pointed to nerve cells' fatty membranes; the main targets are now thought to be proteins.

A general anesthetic usually begins with a fast-acting injection that puts the patient under; what is this stage called?

Induction. A drug injected into a vein, an approach dating from the 1930s, puts a patient under within about a minute; gas through a mask is now the fallback when a vein is hard to find.

The pulse oximeter clipped to a finger during anesthesia reads the blood's oxygen level using what?

Beams of light. Oxygen-rich and oxygen-poor blood absorb red and infrared light differently, a trick Japanese engineer Takuo Aoyagi turned into a bedside monitor in the 1970s.

What is sedation with benzodiazepines commonly nicknamed?

Twilight anesthesia. The patient stays drowsy but can answer the team and breathe unaided, yet often remembers little afterwards; painkillers are added because the sedatives don't dull pain.

An epidural stops outside the spine's protective membranes; a spinal anesthetic is injected through them into what?

The cerebrospinal fluid. A spinal is a single shot into the fluid of the subarachnoid space and works almost at once; an epidural's thin tube stays in place so the dose can be topped up.

Why does blood pressure commonly drop after a spinal or epidural block?

It causes arterial and venous vasodilation. The drug also numbs the nerves that keep blood vessels tight, so the vessels relax and less blood flows back to the heart.

Anesthetists give every surgical patient an ASA grade from 1 to 6; what does it rate?

Their overall health. Grade 1 is a fit, healthy person and grade 6 a brain-dead organ donor; the scale dates from 1941, when anesthetists wanted one shared yardstick for comparing their results.

What do anesthetists call the final phase of a general anesthetic, when the patient wakes?

Emergence. Waking is more than the drugs wearing off: a 2014 study of anesthetised rodents found the brain steps through a set of activity 'hubs' in order before consciousness returns.

Postoperative cognitive dysfunction, a mental fog that can linger for months after major surgery, mainly threatens which patients?

Adults over 60. Its cause is still unclear: the body's inflammatory response to the operation is a leading suspect, and the anesthetic itself may not be to blame.

Which ancient people are said to have cultivated the opium poppy as early as 3400 BCE?

The Sumerians. They are said to have called the poppy hul gil, the 'joy plant', and to have passed it on to the Assyrians, though some scholars doubt the term meant opium at all.

The 2nd-century Chinese surgeon Hua Tuo reportedly knocked patients out by dissolving his herbal powder mafeisan in what?

Wine. The recipe died with him: the warlord Cao Cao had Hua Tuo executed, his writings were burned, and the formula has been lost ever since.

What are Inca shamans said to have chewed and spat into skull wounds to numb them?

Coca leaves. No record confirms the practice, only later suggestion, but the surgery itself was real and skilled: about four in five Inca-era patients survived having their skulls opened.

What was the medieval soporific sponge soaked in?

Opium, mandragora and hemlock juice. The sponge was dried, then wetted again just before surgery and held to the patient's nose until sleep came.

Which 16th-century physician noted that chickens dosed with ether fell into a long sleep and woke unharmed?

Paracelsus. He wrote that his 'sweet vitriol' quieted suffering and relieved pain, yet never tried it on patients; the jump from chicken to operating table took another 300 years.

Who discovered nitrous oxide in 1772?

Joseph Priestley. He made the gas by heating iron filings dampened with nitric acid but never tried breathing it himself, so its strange effects went unnoticed for a quarter of a century.

Which chemist experimented on himself with nitrous oxide in 1799 and gave the gas its famous nickname?

Humphry Davy. Breathing the gas dulled the ache of a wisdom tooth, and he wrote that it might be used in surgery, a hint nobody followed up for more than 40 years.

Why did Hanaoka Seishu's 1804 general anesthetic stay unknown in the West for decades?

Japan was closed to foreigners until the 1850s, by which time the West had ether. Hanaoka had spent some 20 years perfecting his herbal brew, and his wife, who volunteered to test it, lost her sight.

The first documented patient under general anesthesia, a 60-year-old Japanese woman in 1804, had which disease?

Breast cancer. Kan Aiya slept through the removal of her tumour and went home, and her surgeon went on to perform more than 150 such operations before his death in 1835.

Which Georgia doctor removed a tumor under ether on 30 March 1842 but did not publish until 1849?

Crawford Long. He held back because he wanted to repeat the result until he was sure, and so lost the credit in his lifetime; National Doctors' Day now falls on 30 March, the date of his operation.

Which dentist's 1845 demonstration of nitrous oxide in Boston failed when the patient cried out?

Horace Wells. A day after watching a showman's volunteer injure his leg without noticing, Wells had his own wisdom tooth pulled painlessly; the Boston failure brought ridicule that hurt him deeply.

Who gave the first successful public demonstration of ether anesthesia on 16 October 1846?

William T. G. Morton. He nearly missed it, arriving late because he was still adjusting his inhaler; he later asked Congress for a $100,000 reward, but rival claimants blocked it.

What did surgeon John Collins Warren reportedly say after the 1846 public demonstration of ether?

Gentlemen, this is no humbug. No eyewitness report from 1846 records the line; it first appeared in an 1859 biography, three years after Warren's death, and historians doubt he ever said it.

Under what invented name was ether patented in 1846 to disguise what it really was?

Letheon. The name borrowed the Greek word for forgetfulness, as in the mythical river Lethe, but the vapour was soon recognised as plain ether, and surgeons used it freely whatever the patent said.

Why are patients told not to eat for hours before a general anesthetic?

Stomach contents can enter the lungs. Anesthesia switches off the gag and cough reflexes that guard the airway; the lung injury that can follow is named after Curtis Mendelson, who described it in 1946 in women anesthetised in labour.

Who proposed the words anesthesia and anesthetic in an 1846 letter?

Oliver Wendell Holmes. 'Everybody wants to have a hand in a great discovery,' the Boston physician and poet wrote, offering only a name; his son and namesake became a Supreme Court justice.

Which Scottish obstetrician first demonstrated the anesthetic properties of chloroform on humans in 1847?

James Young Simpson. He and two assistants inhaled it one evening in the dining room of his Edinburgh home and all passed out; within weeks he had published his account.

Which monarch received chloroform from John Snow in childbirth in 1853?

Queen Victoria. She called the chloroform 'soothing, quieting and delightful beyond measure' at Prince Leopold's birth, and her example helped make pain relief in labour respectable.

John Snow, a pioneer of anesthesia, traced an 1854 cholera outbreak in London's Soho to what?

The Broad Street water pump. Snow mapped the deaths clustered around it and had the handle taken off; brewery workers and workhouse inmates nearby, who drew their water elsewhere, were spared.

A 2004 study found that women with which natural hair colour needed about a fifth more anesthetic gas?

Red. The study covered just 20 women, though; two later studies of hundreds of surgical patients found that redheads needed no more anesthetic than anyone else.

Alice Magaw, the nurse known as the 'Mother of Anesthesia', worked for which famous American brothers?

The Mayo brothers. Magaw refined the art of dripping ether onto a gauze mask at their Minnesota hospital, and her 1906 review covered more than 14,000 anesthetics without one death from the anesthetic.

Which was the first effective local anesthetic?

Cocaine. In 1884 the Viennese eye doctor Karl Koller showed it could numb the eye for surgery, and the '-caine' ending of later numbing drugs was borrowed from its name.

Whose 1884 paper noted a drug's numbing power in passing, leaving a colleague to discover local anesthesia?

Sigmund Freud. His paper praised the drug as a remedy for many ills; his Vienna colleague Karl Koller tried it on the eye months later and took the credit.

The 'novocaine' patients expect at the dentist today is usually which newer drug, first made in Sweden in 1943?

Lidocaine. Swedish chemists Nils Löfgren and Bengt Lundqvist made it in 1943, and it proved such an advance on procaine, the real Novocain, that it has been the dentist's standard ever since.

Which arrow poison became a surgical muscle relaxant after a Montreal team used it in a 1942 appendectomy?

Curare. It only paralyses muscle, leaving pain and awareness untouched, so Harold Griffith's team gave it on top of an ordinary anesthetic, and it transformed operating conditions for surgeons.

Which milky-white IV anesthetic, first sold as Diprivan, is an emulsion of soybean oil and lecithin?

Propofol. Making it injectable took years and nearly sank the project; developer John Glen kept it alive, and patients wake from it so fast and clear-headed that it became the most used drug for starting anesthesia.

Which musician's 2009 death from an anesthetic plus benzodiazepines drew attention to the drug's off-label use?

Michael Jackson. His doctor, Conrad Murray, had been giving him the surgical anesthetic at home as a nightly sleep aid, and was convicted of involuntary manslaughter in 2011.

Which anesthetic induces a dissociative trance while preserving breathing and airway reflexes?

Ketamine. Patients can look awake yet register nothing around them; because breathing carries on unaided, the drug is a mainstay of emergency and trauma care.

Before anesthesia, London surgeon Robert Liston was celebrated above all for which quality at the operating table?

Speed. With patients awake and strapped down, he is said to have taken off a leg in two and a half minutes; in December 1846 he tried ether for an amputation and declared that the 'Yankee dodge' beat mesmerism hollow.

Why do dentists' local anesthetic injections often contain a small dose of adrenaline?

To make the numbness last longer. Adrenaline narrows the blood vessels around the injection, so the drug is carried away more slowly and the gum bleeds less while the dentist works.

Which drug is the specific treatment for malignant hyperthermia, a rare reaction to volatile anesthetics?

Dantrolene. It blocks the runaway release of calcium inside muscle cells that makes them burn energy and overheat; a reaction that once killed most patients now kills about one in twenty.

Which famous 19th-century anesthetic remained in wide clinical use into the 21st century?

Laughing gas. Nitrous oxide is still breathed in dental chairs and delivery rooms, while chloroform's habit of upsetting the heart's rhythm drove it from the operating room.

Which US president had a tumour secretly cut from his jaw under ether aboard a friend's yacht in 1893?

Grover Cleveland. Fearing the news would deepen a financial panic, he vanished for four days; surgeons worked through his mouth so no scar would show, and a reporter's account was denied until a surgeon confirmed it 24 years later.

What kept August Bier in bed for days after trying spinal anesthesia in 1898?

Headache. He had let his assistant try the needle on him; Bier traced the pain to the puncture it leaves behind, and today's much finer needles make such headaches far less likely.

What did the FDA warn in 2016 about repeated or lengthy anesthesia in children under three?

It may affect brain development. The warning rested largely on animal studies; a later international trial found that about an hour of anesthesia in infancy made no difference to children's development at age five.

The word 'anesthesia' was built from Greek roots that literally mean what?

No sensation. It joins an-, 'without', to aisthesis, 'feeling', the root that also gave us 'aesthetic'; the word sat in medical dictionaries for over a century before surgeons had the means to earn it.

A dentist who numbs one whole side of the lower jaw at once is using which technique?

A nerve block. The drug is placed beside the nerve trunk before it enters the jawbone, so every tooth it supplies goes numb at once; infiltration, by contrast, soaks through the bone around a single tooth.

Which naturalist abandoned his medical studies in the 1820s after fleeing operations performed without anesthesia?

Charles Darwin. At Edinburgh he rushed out of two operations, one on a child, and never went back, writing later that this was 'long before the blessed days of chloroform'.

Which injected drug, first given in 1934, became the standard way to put surgical patients to sleep for decades?

Sodium Pentothal. Chemists at Abbott made the drug, properly called thiopental, and it worked in well under a minute; popular culture later made it famous as a 'truth serum', a power experts doubt it has.

Where did anesthetist Arthur Guedel put his sleeping dog to show his cuffed breathing tube worked?

Water tank. The inflated cuff sealed the windpipe, so the anesthetised dog could be kept breathing through the tube while fully submerged, and it came out unharmed.

What does an anesthetist use a Macintosh blade for?

Inserting a breathing tube. Designed in 1943 and still the most widely used of its kind, the blade never cuts: its curved tip lifts the epiglottis clear to show the vocal cords.

Which Belgian pharmacologist's team synthesised fentanyl around 1960?

Paul Janssen. Fentanyl turned out roughly 100 times as potent as morphine and became one of the world's most widely used opioids, first in operating rooms and later, disastrously, on the street.

Halothane, introduced in 1956, had what major safety advantage over ether and cyclopropane?

It was not flammable. Ether and cyclopropane vapour could catch fire or explode in the operating room; halothane ended that risk, until rare cases of severe liver damage saw newer agents take its place.

Which effect did Harvard anesthetist Henry K. Beecher bring to wide attention with a famous 1955 paper?

The placebo effect. His paper claimed that about a third of patients improved on dummy treatment, and medicine took the effect as fact; a 1997 re-analysis found no real placebo effect in his data.

In Copenhagen's 1952 polio epidemic, what did hundreds of medical students do around the clock to keep paralysed patients alive?

Squeeze air bags by hand. Anesthetist Bjørn Ibsen had the air pushed in through a tube in the windpipe; deaths fell from nearly nine in ten to well under half, and the wards set up for the patients grew into intensive care.

Which non-greenhouse noble gas won approval as an anesthetic in Europe in the 2000s?

Xenon was approved in Germany in 2005 and more widely in Europe in 2007. The 21st century also brought video laryngoscopes such as the Glidescope, which use digital sensors to view the glottis.

Veronal, a sleeping pill Bayer sold from the early 1900s, was the first of which drug family?

Barbiturates. They were the mainstay sleeping pills and sedatives until about 1960, when benzodiazepines, far less deadly in overdose, began to replace them; a few survive in anesthesia and epilepsy.

Which anesthesiologist devised the ten-point score, introduced in 1952, for assessing newborn babies?

Virginia Apgar gave the score her name, and about ten years later its five checks were fitted to the letters of that name as a memory aid: Appearance, Pulse, Grimace, Activity, Respiration.

Which English architect gave the first successful injection into a bloodstream, to a dog in the 1650s?

Christopher Wren ran ale into a dog's vein until it was thoroughly drunk, two centuries before injected drugs reached the operating room. The dog survived, grew fat and was later stolen.

Which street drug, nicknamed angel dust, did Parke-Davis develop in the 1950s as a surgical anesthetic?

PCP caused such high rates of side effects that its use in humans was barred in the United States in 1965, though vets went on using it on animals until 1978.

John Bonica, the anesthesiologist who founded pain medicine, paid for his studies through which sport?

Wrestling at carnivals as the Masked Marvel paid for his degree; a chronic pain sufferer himself, Bonica went on to champion clinics where several specialties treat pain together.

Which medical technique did Austrian-born anesthesiologist Peter Safar pioneer in 1950s Baltimore?

CPR owes its rescue-breathing step to Safar's experiments on paralysed volunteers, and he persuaded a Norwegian doll maker to build the Resusci Anne training mannequin.

Besides calming dental patients, nitrous oxide propels which dessert topping out of aerosol cans?

Whipped cream suits the gas because nitrous oxide dissolves readily in fat: it stays hidden in the cream under pressure, then bubbles out as foam the moment it exits the can.

Morphine, first isolated from poppies in 1804, is named after Morpheus, the Greek god of what?

Dreams were the realm of Morpheus, and chemist Friedrich Sertürner chose the name because the drug made his test animals drowsy. He later tried it on himself and three boys, and all four nearly died.

Why can a patient stay awake and chatting while a neurosurgeon cuts into the brain's own tissue?

It has no pain receptors, which lets surgeons use the patient's speech and movement as a live map of which tissue is safe to remove.

When Ronald Reagan had colon surgery under general anesthesia in 1985, who served as acting president?

George Bush, then vice president, held the powers of the office from 11:28 a.m. until 7:22 p.m., when Reagan signed a letter declaring himself able to resume his duties.

The 'dural' in epidural comes from the dura mater, a Latin name that literally means what?

Tough mother is a medieval translation of an Arabic phrase for the thick outer membrane of the brain and spinal cord, the layer an epidural needle stops just short of.

Which now-standard hospital unit did anaesthetist Bjørn Ibsen first set up in Copenhagen in 1953?

Intensive care began in a converted student nurses' classroom, a year after a polio epidemic taught Ibsen that round-the-clock breathing support could keep paralysed patients alive.

In which 1999 film does Michael Caine play an orphanage doctor addicted to inhaling ether?

The Cider House Rules won Caine his second Oscar for playing Dr Wilbur Larch, who runs a Maine orphanage during the Second World War.

Which drug, sold as Narcan, reverses the breathing depression caused by an overdose of opioid painkillers?

Naloxone blocks opioids at the sites where they act; given into a vein it starts to work within two minutes, against about ten for the nasal spray.

Ondansetron (Zofran) is given during surgery to prevent which common after-effect of anesthesia?

Nausea and vomiting strike about 30% of untreated patients after a general anesthetic, with women, non-smokers and people prone to motion sickness at higher risk.

Hospital fasting orders before surgery use the abbreviation NPO, short for a Latin phrase meaning what?

Nothing by mouth translates the Latin nil per os, and the same order is written for patients with a blocked intestine or acute pancreatitis.

Atropine, which anesthetists inject to quicken a slow heartbeat, occurs naturally in which poisonous plant?

Deadly nightshade carries the drug in its Latin name, Atropa belladonna; 'beautiful woman' recalls the plant's Renaissance use as a cosmetic for widening the pupils.

Capnography, a routine monitor during general anesthesia, tracks which gas in each breath a patient exhales?

Carbon dioxide on the trace proves that air is moving in and out of the chest, so the monitor catches a tube placed in the gullet by mistake sooner than clinical judgement alone.

Before ether arrived, London physician John Elliotson promoted which practice for operating without pain?

Mesmerism cost Elliotson his post at University College Hospital in 1838, but his journal The Zoist kept reporting amputations carried out on entranced patients.

Which arteries take their name from a Greek verb meaning to plunge into deep sleep?

Carotid arteries carry blood up the neck to the brain, and the name records what happens when that flow is interrupted: the victim loses consciousness.

In the United States, about half of all anesthesia providers hold which nursing credential?

CRNA stands for Certified Registered Nurse Anesthetist; nurses have been putting American patients to sleep since the Civil War and are the main providers in rural areas.

Which American gun maker earned his living as a young man by touring with nitrous oxide shows?

Samuel Colt took a portable laboratory across the United States and Canada, starting on street corners and working up to lecture halls, years before his revolver made him rich.

Etorphine, an opioid far too strong for human medicine, is used by vets mainly to immobilise which animals?

Elephants and other large mammals can be immobilised with it, but veterinary-strength etorphine is fatal to humans and its side effects have pushed it out of general practice.

The Trendelenburg position, named after a German surgeon, tilts a patient on the operating table in which way?

Feet above the head, on a slope of 15 to 30 degrees, lets gravity pull the abdominal organs away from the pelvis so that a surgeon has room to work there.

Which American writer's wife Fanny received the first obstetric anesthetic in the United States, in 1847?

Henry Longfellow's wife was given ether by Nathan Cooley Keep, a dentist who went on to become the founding dean of Harvard's dental school.

Which pre-surgery drug, also worn as a motion-sickness patch, was tested as a truth serum in the early 20th century?

Scopolamine dries up secretions before an operation, and interrogators dropped it because of its side effects; in powdered form it goes by the nickname devil's breath.

Heavy, repeated use of nitrous oxide can damage nerves by inactivating which nutrient?

Vitamin B12 is switched from its active form to an inactive one by the gas, which is why chronic abuse can lead to neurological damage.

Succinylcholine, nicknamed 'sux', is injected at the start of many operations to do what within a minute?

Paralyse the body, briefly: the drug works within a minute and wears off in about ten, just long enough to pass a tube into the windpipe.

Which benzodiazepine, sold as Versed, is given before surgery to calm patients and blur their memory of it?

Midazolam stops new memories forming for a while, and patients are generally unaware that anything is missing unless they were told about the side effect beforehand.

Who plays the patient who is conscious but paralysed during heart surgery in the 2007 thriller Awake?

Hayden Christensen starred opposite Jessica Alba as a man who overhears a plot to kill him on the operating table; the pair were nominated for a Razzie as Worst Screen Couple.

What name did Arthur Guedel give stage two of ether anesthesia, the phase just after consciousness is lost?

Excitement, also called delirium, can bring coughing, struggling and breath-holding. Guedel defined the stages while teaching nurses and orderlies at the army hospitals he toured by motorcycle.

Most volatile anesthetics have been found to activate which receptor in the brain?

GABA-A receptors are chloride channels that quieten nerve cells when they open, yet the exact site where the gases act on them remains unknown.

Which antidote, first marketed in 1987 as Anexate, reverses an overdose of benzodiazepine sedatives?

Flumazenil competes with the sedative for the same recognition site, and it is also given simply to help bring a drowsy patient round after a procedure.

Sellick's manoeuvre, used as emergency patients go under, presses on which ring of cartilage?

Cricoid pressure squeezes shut the gullet lying directly behind the ring; anaesthetist Brian Sellick described the technique in a 1961 paper.

Which drug, the first of its class, reverses the muscle relaxant rocuronium by encapsulating its molecules?

Sugammadex is a modified cyclodextrin, a ring of sugar units with a fat-loving core, and its grip on rocuronium is among the strongest known for such molecules.

Which injected anesthetic from 1964 is favoured for unstable patients because it barely lowers blood pressure?

Etomidate keeps the circulation steady, but it also directly blocks the adrenal gland's production of steroid hormones, a drawback linked to deaths when it was run as a long infusion.

The 1846 ether demonstration that launched surgical anesthesia took place at which American hospital?

Massachusetts General used the room for operations until 1868; later a storeroom, a dormitory and a nurses' dining room, it survives as a teaching space called the Ether Dome.

Which British king's coronation was postponed in 1902 for an emergency appendix operation under anesthesia?

Edward VII fell ill two days before the ceremony; surgeon Frederick Treves drained the abscess, and the king's recovery brought appendix surgery into the medical mainstream.

Which volunteer lost her sight testing the herbal anesthetic that surgeon Hanaoka Seishu first used in 1804?

His wife's sacrifice inspired Sawako Ariyoshi's novel The Doctor's Wife, later filmed, which imagines her competing with Hanaoka's mother over who should be tested.

At which university did Ralph Waters set up America's first academic department of anesthesia, in 1927?

Wisconsin recruited Waters on the strength of his reputation, and alongside the new department he established a training programme for resident doctors in the specialty.

The Latin motto of Britain's Royal College of Anaesthetists declares that it is divine to do what?

Alleviate pain renders the Latin sedare dolorem; on the college's coat of arms the shield is held up by two Victorian pioneers of the specialty, John Snow and Joseph Clover.

Which anaesthetist gave his name to the continuous-flow anesthesia machine he built in London in 1917?

Henry Boyle built his own after finding the American Gwathmey machines he had imported unreliable; his design carried the gas cylinders and a 'Boyle's Bottle' for vaporising ether.

The pin index safety system on an anesthesia machine's gas yokes exists to prevent which mistake?

Fitting the wrong cylinder is blocked because each gas has its own pattern: two pins on the yoke must line up with two holes drilled in matching positions on the cylinder valve.

Which volatile anesthetic needs its own heated, pressurised vaporizer because it boils at about room temperature?

Desflurane boils at 23.5 °C, so on a warm day an ordinary vaporizer could release a potentially lethal dose. Its special unit heats the liquid to 39 °C and stops working if mains power is lost.

What is the job of the scavenging system connected to an anesthesia machine in the operating room?

Removing waste gases protects the staff rather than the patient: most jurisdictions set a legal limit on how much anesthetic vapour may build up in the operating room air.

The Bain circuit, often used with anesthesia machines, is a coaxial form of which of William Mapleson's 1954 categories?

Type D circuits are efficient when a ventilator or a squeezing hand does the breathing, but need far more fresh gas when patients breathe for themselves.

Which granular chemical in an anesthesia machine's canister cleans exhaled gas and changes colour when used up?

Soda lime lets the machine recirculate a patient's breath, and the same granules do the job in submarines and divers' rebreathers. A standard machine holds up to 2 kg.

Which German company, founded in Lübeck in 1889, developed an early anesthesia apparatus in 1902?

Dräger named the 1902 apparatus jointly after a Lübeck doctor, Otto Roth, and it stayed in use in Germany until the end of the Second World War.

Interlocks between the vaporizers on an anesthesia machine stop the anesthetist from making which mistake?

Giving two agents at once is ruled out because each vaporizer is calibrated for a single liquid, and a mixture of two would make its output unpredictable.

The rotameters on an anesthesia machine, tapered glass tubes with a float inside, measure what?

Gas flow rate is read from how high the float sits: the stream pushes it up the tube while gravity pulls it down, a design Karl Kueppers invented in Aachen in 1908.

The APL valve in an anesthesia machine's breathing circuit lets excess gas escape; what does APL stand for?

Adjustable pressure-limiting describes the job: the anesthetist sets how much pressure may build before gas spills out, while the valve keeps room air from leaking in.