[The spontaneous and evoked EEG in anesthesia].
Clear differentiation between nociception and pain, or, better, between anti-nociception and pain relief, is essential for understanding the analgesic mechanisms in anaesthesia. Nociception is a neuronal activity in the pain-mediating and pain-processing nervous system, i.e. in the peripheral axons, in the spinal short cord and in certain brain structures. The nociceptive system has been well documented by experiments, especially in animals. If this system is specifically blocked, there will be no transmission and hence no sensation of pain if we leave aside the rare and complicated instances of "psychogenic pain". Nociceptive activity is blocked or at least attenuated by anti-nociceptive drugs, such as surface anaesthetics acting in the periphery by blocking the sodium channels in the conductive nerve membrane. Opiates are another example of drugs which develop an effect on specific nociceptive neurons in the spinal cord and in the brain, thus suppressing pain transmission. An ideally effective anaesthetic should act similarly, that is by specifically and selectively suppressing nociceptive activity induced by surgery. However, general anaesthesia is based on entirely different mechanisms. It lowers the arousal level, or the vigilance of the patient. Since pain is the conscious processing of nociceptive information, attenuating the vigilance also alleviates pain; there is no pain without consciousness. Most of the centrally acting analgesics will also reduce vigilance; e.g. driving is not permitted under analgesia with opiates. Alcohol is another example, although it minimally affects the nociceptive system, it substantially lowers the vigilance, thereby alleviating pain.(ABSTRACT TRUNCATED AT 250 WORDS)
Bromm
B
B
Physiologisches Institut, Universität Hamburg.
D000777:Anesthetics / Q000494:pharmacology*; D016208:Databases, Factual; D004569:Electroencephalography / Q000187:drug effects*; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects* / Q000502:physiology; D005858:Germany; D006801:Humans; D010146:Pain / Q000188:drug therapy / Q000503:physiopathology*
D000777:Anesthetics