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The book presents general anaesthesia as a combination of distinct effects, unconsciousness, pain relief and immobility, often produced by separate drugs. Because muscle relaxants paralyse the body whether or not the mind is switched off, a patient can be conscious and unable to signal it. This is the gap in which the book's cases of intraoperative awareness occur.
In the isolated forearm technique, a tourniquet keeps paralysing drugs out of one arm, so a supposedly anaesthetised patient can still move that hand. Some patients squeeze on command mid-operation, showing they can hear and respond, yet afterwards remember nothing. This shows that responsiveness during surgery and memory of it are separate questions.
In 1965 Bernard Levinson had an anaesthetist announce, during surgery, that a patient was turning blue and in danger. Weeks later, under hypnosis, several of these patients reproduced the words or became distressed, though none recalled the event consciously. The experiment suggested that anaesthetised patients can register and keep meaningful speech without conscious memory.
If anaesthetised patients may still take in speech, then what surgeons and staff say beside an unconscious body is a possible input, not harmless background noise. Careless remarks could do harm, and deliberate reassurance or positive suggestion could help recovery. This changes bedside talk from a matter of manners to a clinical variable.
Anaesthetists can reliably produce and reverse unconsciousness millions of times a year, yet no one fully understands how these drugs switch consciousness off. Depth monitors estimate brain states indirectly and cannot confirm whether anyone is experiencing anything. Anaesthesia therefore puts the unsolved problem of consciousness into everyday medical practice.