anaesthesia

   Also written as anesthesia. The term anaesthesia comes from the Greek noun anaisthèsia,which means numbness. In a broad sense, it refers to a loss or impairment of sensitivity to stimuli in any of the sensory modalities. As a rule, however, the term is used in a more restricted sense, to denote a loss or impairment of sensitivity to stimuli in the somatosensory modality. These stimuli can be of a tactile, thermal, chemical, or any other origin. Some examples of anaesthesia are insen-sitivity to needle pricks or cuts, to hot or cold stimuli, and indifference to ammonia held under the nose. Etiologically, the mediation of anaesthesia is associated with either peripheral or central nervous tissue damage (or tissue manipulation, as in acupuncture), with the administration of anaesthetics or other chemical substances, or with psychological mechanisms. Some examples of psychological mechanisms capable of inducing anaesthesia are stress, suggestion, "ecstasy, "trance, rapture, hypnotic states, "dissociation, somnambulism, conversion, and "psychosis. It has long been debated whether psychologically induced anaesthesia is comparable to 'true' (i.e. measurable, physiological) anaesthesia, or to a kind of role-playing behaviour, where the subject acts as if the stimulus in question has not been perceived. However, measurements of physiological reactions as well as functional imaging studies would seem to indicate that psychologically induced anaesthesia leads to actual, though reversible organic changes. The term anaesthesia is used in opposition to the term " hyperaesthesia. The specific loss or impairment of sensitivity to painful stimuli is usually referred to as " analgesia. For the specific loss or impairment of sensitivity to temperature, the term thermoanaesthesia is used. The terms " total anaesthesia, generalized anaesthesia, and systematized anaesthesia are reserved for psychologically induced states of total body numbness, such as those described in classical studies on hypnotism and hysteria. Total anaesthesia should not be confused with " acenesthesia, which is conceptualized as a condition characterized by a total loss of awareness of physical existence, and with Cotard's syndrome, a condition in which the affected individual can have the delusional conviction (rather than the perceptual experience) that his or her body has ceased to exist.

   References

   Janet, P. (1911). L'état mental des hystériques. Deuxième édition. Paris: Félix Alcan. Wolberg, L.R. (1948). Medical hypnosis. Volume I. The principles of hypnotherapy. New York, NY: Grune & Stratton.

   Wobst, A.H.K. (2007). Hypnosis and surgery: Past, present, and future. Anesthesia and Analgesia, 104, 1199-1208.