There was a time when all the pain alleviation involved in surgery was a little cotton wool in the surgeon's ears to keep the screams of the patient from hurting them. Fortunately, things have changed.
How did we get from biting down on a stick, to today's modern, anesthetized operating rooms? Here's the often weird history of humans' efforts to end pain.
Most historical military films have at least on scene in which someone screams in pain, fully conscious, as a surgeon hacks off a limb with a saw. Those scenes happened, it's true, but most often under conditions of extreme deprivation, like wars in which the many injuries make supplies scarce. As long as people have been performing medical procedures on each other, they've had something on hand to kill the pain. The effectiveness of that 'something' varies. Some people were lucky enough to get their hands on hard stuff, like opium, cocaine, or marijuana. The Incas managed to drill holes in the heads of patients with relatviely little pain by chewing coca leaves and spitting into the wounds. Most patients, however, were not so lucky. Alcohol was sometimes used, but the really unlucky people had to make due with folk-anesthetics like mulberry and lettuce. Imagine that. "I'm going to have to saw off your foot - have some lettuce."
Doctors, before around 1800, also used techniques to numb a limb, like compressing it to cut off blood flow and sensation, or numbing it with cold. Some preferred the direct approach and straight up knocked people unconscious with a hit to the head. For the more delicate types, good surgeons offered unconsciousness by strangulation. That's better than lettuce, but it's less than ideal. Still, when faced with the prospect of unanesthetized dental surgery or being held down while a wound was cauterized, the prospect of a quick death by concussion was welcomed. Medical care might not have been worth getting before the 1800s. Until then the most commonly used anesthetics in industrialized nations were alcohol and opium, and neither numbed completely.
Going Ethereal
Ether, as a substance, was first discovered all the way back in 1275. It was synthesized in the fifteen hundreds, but the gas wasn't officially used in surgeries until the 1800s. March 30, 1842 was a very good day for everyone awaiting surgery. Crawford Long publicly administered ether to a man undergoing surgery for a tumor. Though notes were made about how the man moved and 'made extraordinary expressions', he didn't scream like someone whose body was being cut into, and that's what the doctors were looking for.
Diethyl ether is now used as a laboratory solvent. Even then it has to be used carefully. Long exposure to it can cause vomiting and drowsiness, and ether is heavier than air, so if someone exposed to leaked ether passes out, they can be smothered. Just as an added bonus, it's highly flammable, so it can cause fires or explosions. Still, when making a choice between surgery with ether or surgery without, there are few who choose the former.
Chloroformer
It was ether's flammability that finally stopped the widespread use of ether, especially when chloroform appeared on the horizon. Although chloroform wasn't invented until the 1830s, it quickly overtook the medicinal use of ether. Few doctors liked their offices catching fire or blowing up, of course, but they also found it easier to administer chloroform to their patients. Ether has a strong, unpleasant smell, but chloroform smells sweet. It also works a great deal faster than ether, although its extreme effectiveness resulted in more overdoses.
The correct dosing of chloroform was especially difficult because the body metabolizes it differently depending on how much has been inhaled. A low dose may kill someone while a higher dose may let them live. Extremely low doses, however, would take away pain while keeping a patient conscious, and was administered to women during childbirth. The drug even got a kick of fame for having been given to Queen Victoria during the birth of two of her children.
Laughing Through Surgery
Invented in 1775, nitrous oxide wasn't used in surgeries until Humphry Davy sniffed out its uses in the 1800s. Now that painless surgeries were on everyone's mind, the gas became popular because it didn't have to knock people out to relieve pain. Unlike chloroform and ether, this gas had legs. It's still used in dental surgery and obstetrics, and it's still abused by people who can get their hands on it. A little laugh is a bad bargain, though. Chronic inhalation of nitrous oxide leads to brain and spinal cord damage.
Into the Spine and Into the Veins
By the early twentieth century, huffing went out of fashion. Drugs could be administered more precisely through the injections. The first spinal anesthetic was performed in 1899 by August Bier using cocaine. After some horrifying experimentation they found that their volunteer went completely numb, even when being hit in the shin with a small hammer or rigorous pulling on his testicles. The next fifty years were mostly about making spinal anesthesia more effective and perfecting techniques that could make it continuous, as well as experimentation with intravenous anesthesia.
A real breakthrough came with muscle relaxants. The original muscle relaxant was curare, a plant derivative used in South America as a poison. One of the major dangers of anesthesia was the suppression the human body's reflexive breathing. Muscle relaxants allowed doctors to intubate patients and keep getting oxygen to them during surgery. They also suppressed the body's natural muscle responses, which kept the patient immobilized and allowed doctors to perform a wider variety of surgeries.
Intravenous anesthesia got its first viable option in the 1930s with pentathol, and was refined extensively in World War II. In the 1960s ketamine was introduced - though its now used extensively on animals. Since then, intravenous anesthetics have undergone a slow, steady refining process.
The Ultimate Nightmare
One of the most disturbing - and infamous - problems with modern general anesthesia is its compartmentalization of the drugs. One set of drugs is used to paralyze the body. Another set of drugs is used to render the person unconscious. A trained doctor administers both sets, but it is possible for the drug that paralyzes a patient to work, but the drug that knocks them out to not do its job. Medical horror stories have emerged of people being conscious during surgeries, but completely immobile and unable to signal their pain.
The news on that front is not what most people want to hear - it is possible. But it is unlikely. There are security measures in place. For high-risk surgeries, doctors monitor a patient's brain activity to check for signs of distress. Even for minor procedures, the drugs that immobilize a person are generally only given at the beginning of a procedure. Over time those wear off, and even the least competent surgeon does re-check the patient's level of anesthesia if the patient wakes up screaming.
If that doesn't work - try some lettuce.
Via Disoveries in Medicine, How Stuff Works, eHow, General Anesthesia.com, General Anesthesia.com, Nitrous Oxide, and AAGBI.