Theories Of General Anaesthetic Action
A general anaesthetic (or anesthetic) is a drug that brings about a reversible loss of consciousness. These drugs are generally administered by an anaesthetist/anaesthesiologist in order to induce or maintain general anaesthesia to facilitate surgery.
General anaesthetics have been widely used in surgery since 1842 when Crawford Long for the first time administered diethyl ether to a patient and performed a painless operation. It has always been believed that general anaesthetics exert their effects (analgesia, amnesia, immobility) by modulating the activity of membrane proteins in the neuronal membrane. However, the exact location and mechanism of this action are still largely unknown although much research has been done in this area. There are a number of outdated and modern theories that attempt to explain anaesthetic action.
The concept of specific interactions between receptors and drugs first introduced by Paul Ehrlich states that drugs act only when they are bound to their targets (receptors). However, this concept is not working well in case of general anaesthetics because:
- Molecular structures of general anaesthetics widely used in medicine are very simple and diverse so that there is no obvious structure–activity relationship (see structures of general anaesthetics widely used in medicine: 1-ethanol, 2- chloroform, 3-diethylether, 4-fluroxene, 5-halothane, 6-metheoxyflurane, 7- enflurane, 8-isoflurane, 9-desflurane, 10-sevoflurane)
- Most general anaesthetics have remarkably weak affinity for their targets acting at much higher concentrations than most other drugs so that diverse side effects are inevitable .
All these common features of general anaesthetics made it hard for early researchers to believe that general anaesthetics act in a specific manner and their action on neuronal membrane was thought to be global (through nonspecific perturbation of lipid membrane of CNS neurons) rather than through specific sites.
Read more about Theories Of General Anaesthetic Action: Lipid Solubility-anaesthetic Potency Correlation (the Meyer-Overton Correlation), Outdated Lipid Hypotheses of General Anaesthetic Action, Modern Lipid Hypothesis, Membrane Protein Hypothesis of General Anaesthetic Action
Famous quotes containing the words theories of, theories, general and/or action:
“Our books of science, as they improve in accuracy, are in danger of losing the freshness and vigor and readiness to appreciate the real laws of Nature, which is a marked merit in the ofttimes false theories of the ancients.”
—Henry David Thoreau (1817–1862)
“The egoism which enters into our theories does not affect their sincerity; rather, the more our egoism is satisfied, the more robust is our belief.”
—George Eliot [Mary Ann (or Marian)
“I have never looked at foreign countries or gone there but with the purpose of getting to know the general human qualities that are spread all over the earth in very different forms, and then to find these qualities again in my own country and to recognize and to further them.”
—Johann Wolfgang Von Goethe (1749–1832)
“Virtue is the adherence in action to the nature of things, and the nature of things makes it prevalent. It consists in a perpetual substitution of being for seeming, and with sublime propriety God is described as saying, I A—.”
—Ralph Waldo Emerson (1803–1882)