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general anaesthesiaA state of unconsciousness and immobility, brought about by drugs, so as to allow surgical operations or other physical procedures to be performed without pain or awareness. Deep levels of unconsciousness, formerly necessary to achieve the required degree of muscle relaxation, are no longer used. Light anaesthesia, associated with the use of drugs to relax muscles and prevent pain, shock and autonomic disturbance, is now standard.
The action of general anaesthetic drugs is now better understood. Pain responses are suppressed primarily at spinal cord level; hypnosis and amnesia are mediated by the brain. These drugs are now believed to operate on ion channels in nerve cells by binding directly to the protein sites. Different anaesthetic drugs bind specifically to different ion channels.