Less than 150 years ago, surgery was performed without any anaesthetic. A patient was held down by strong men as he battled to escape from the pain of the surgeon’s knife. Surgeons even resorted to stupefying their patients with alcohol, knocking them unconscious, or freezing the part to be operated on with ice.
The first time an anaesthetic was used was on March 30, 1842, in Jefferson, Georgia, USA, when Dr Crawford Long removed a tumour from the neck of James Venable, who first inhaled ether. But it was only following William Morton’s public demonstration in Boston of the extraction of a tooth under ether, in 1846, that ether became widely adopted as an anaesthetic.
At around the same time in the United States, nitrous oxide, also known as laughing gas and used as a music hail entertainment, was being inhaled as an anaesthetic for dental surgery. In Britain. Research was being done on the uses of chloroform, particularly to relieve the pain of childbirth. Without these early attempts at the use of anaesthetics, many of today’s surgical procedures would not be possible. Now, major operations, such as heart trans; plants, cosmetic surgery and removal,01 cancer, are possible without pain. But just, how do anaesthetics allow people to slip off into a world where pain does not exist?
Anaesthesia derives from the Greek word for ‘lack of feeling’. All anaesthetics induce this condition by blocking the of pain signals to the brain. However, how they actually work is not yet fully understood.
Anaesthetics take two forms — general, which put the patient ‘to sleep’, and local, which affect only part of the body.
Loss of sensation, ox or analgesia may be provided by nitrous oxide, not put the patient to sleep. It may cause mental or physical excitement. Sleep is usually induced by an injected barbiturate. The muscles are then relaxed with a neuroblocker, or muscle relaxant, such as curare.
During surgery, the patient is watched so that any changes in circulation; so that any changes in circulation, breathing or kidney function which may result from the anaesthetic can be regulated.
Local anaesthetics are given as an injection to remove all sensation from and a localised area. The patient is conscious can cooperate with the surgeon.
There are three principal uses of local anaesthetic. Topical anaesthetics remove the sensation from nerve endings in mucous membranes such as those in the eye, the nose and the mouth. They are used, for example, to remove a foreign object from the eye. Nerve-block anaesthetics are injected into a nerve to anaesthetise a small area, for example, to enable a tooth to be extracted. Other anaesthetics are injected into a large nerve group to numb a larger part of the body, such as an arm.
Atoms that transmit pain
A clue to the way general anaesthetics work comes from research into local anaesthetics. These are known to interfere with the way nerve impulses are transmitted a along the nerve fibres. Sodium and potassium atoms play an important pa sending these impulses to the brain. If you stub your toe, for example, the sodium and potassium atoms pass in opposite directions across the membrane of the nerve cell causing the next cell to do the same and so on until the signal reaches the brain, when you feel pain. But local anaesthetics stop the atoms from passing in and out of the nerve cell, so no pain signal reaches the spinal cord.
Scientists think that general anaesthetics may cause unconsciousness by suppressing the activity of certain enzyme in the nerve cells, or changing the prop of the nerve-cell membranes, or even by interacting with water molecules in the brain to form small crystals which affect the path of a signal along a nerve cell. Research. Continues into the exact -mechanism, but what is certain is that without anaesthetics a great deal of surgery could never he performed.
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