The first person who operated under anaesthesia was William Thomas Morton, the 16th October 1846, to remove a tumour from the neck to a patient.
ANAESTHESIA ALONG HISTORY
Before anaesthesia ( it means "without pain") was discovered, there were many ways to relieve pain in patients suffering operations such as to remove a tooth, to draw an arrow or draw a member with gangrene. Alcohol, marijuana, opium, to knock the patient or grab him were the ways which were used to operate.
Along history, people have used different inhalation anaesthetics, but they are very dangerous to humans because they can die in the operation, so this type of general anaesthesia is only used if the operation is more important and advanced. In general, it's used local intravenous anaesthesia, which blocks the nerves of the area that we want to operate.
STAGES OF GENERAL ANAESTHESIA
When the anaesthesia is injected, there are four stages which the person experiences:
*Stage analgesia --> Muscle relaxation is minimal. In this stage, the person becomes unconscious.
*Stage delirium --> Breathing is irregular
*Stage surgical anaesthesia --> Irregular breathing stops and this stage lasts until spontaneous breathing stops.
*Stage marrow depression --> Spontaneous breathing stops and the patient may end up in respiratory failure.
Another type of anaesthesia is the epidural, which is applied in the air surrounding the lower spinal cord, which eliminates the sensation of pain in the abdomen and legs. It started to be used in childbirth to prevent pain to pregnant women, but today it's used in many different operations.
You can see more information about the anesthesia here