Endogenous anesthetics are analogs of anesthetics the body makes that have the properties and similar mode of action of general anesthetics.[1]

Types of endogenous anesthetics

Carbon dioxide

Carbon dioxide (CO2) is an abundant gas produced as the final product of glucose metabolism in animals. CO2 anesthesia is most frequently used for anesthetizing flies.[2] But it has also been considered as a fast acting anesthetic in small laboratory animals.[3]

In the 1900s, CO2 anesthesia, known as CO2 therapy was used by psychiatrists for the treatment of anxiety. The patients would receive 70% CO2 in combination with 30% oxygen causing rapid and reversible loss of continuousness.[4]

Ammonia

Ammonia has also been shown to have anesthetic properties.[5]

Mechanism of action

The most abundant endogenous anesthetics are small hydrophobic gaseous metabolites of catabolism and likely work through a membrane-mediated mechanism of general anesthesia.

In the 1800s anoxia was considered the mechanism of CO2 anesthesia.[6] However, studies in humans showed the opposite, oxygenation of the brain tissue increases with increase CO2 in the lung.[7] More recent studies have shown in bees that anoxia is also not the mechanism.[8]

In humans, CO2 raises the threshold of stimulation of the nerve cell, decreases the speed of conduction of impulses along the nerve, and increases the height and prolonged duration of the action potential.[9]

While the endogenous anesthetics appear to have a similar mechanism of action to inhaled anesthetics, their rapid endogenous metabolism complicates their use in humans. Apart from flies, exogenous compounds have proven more useful for maintaining general anesthesia.

History

The first private demonstration of an anesthetic was carbon dioxide by Henry Hill Hickman in a dog cerca 1823.

References

  1. ↑ Lerner, Richard A. (9 December 1997). "A hypothesis about the endogenous analogue of general anesthesia". Proceedings of the National Academy of Sciences. 94 (25): 13375–13377. doi:10.1073/pnas.94.25.13375. PMC 33784.
  2. ↑ Nilson, Theresa L.; Sinclair, Brent J.; Roberts, Stephen P. (October 2006). "The effects of carbon dioxide anesthesia and anoxia on rapid cold-hardening and chill coma recovery in Drosophila melanogaster". Journal of Insect Physiology. 52 (10): 1027–1033. doi:10.1016/j.jinsphys.2006.07.001. PMC 2048540.
  3. ↑ Kohler, I.; Meier, R.; Busato, A; Neiger-Aeschbacher, G.; Schatzmann, U. (1 April 1999). "Is carbon dioxide (CO2) a useful short acting anaesthetic for small laboratory animals?". Laboratory Animals. 33 (2): 155–161. doi:10.1258/002367799780578390.
  4. ↑ LAVERNE, AA (May 1953). "Rapid coma technique of carbon dioxide inhalation therapy". Diseases of the nervous system. 14 (5): 141–4. PMID 13052042.
  5. ↑ Brosnan, Robert J.; Yang, Liya; Milutinovic, Pavle S.; Zhao, Jing; Laster, Michael J.; Eger, Edmond I.; Sonner, James M. (June 2007). "Ammonia Has Anesthetic Properties". Anesthesia & Analgesia. 104 (6): 1430–1433. doi:10.1213/01.ane.0000264072.97705.0f.
  6. ↑ Antiquack (1826). "Surgical Humbug". The Lancet. 5 (127): 646.
  7. ↑ Moriarty, John D. (April 1954). "EVALUATION OF CARBON DIOXIDE INHALATION THERAPY". American Journal of Psychiatry. 110 (10): 765–769. doi:10.1176/ajp.110.10.765.
  8. ↑ Cressman, Anna; Amsalem, Etya (1 January 2023). "Impacts and mechanisms of CO2 narcosis in bumble bees: narcosis depends on dose, caste and mating status and is not induced by anoxia". Journal of Experimental Biology. 226 (1). doi:10.1242/jeb.244746.
  9. ↑ Moriarty, John D. (April 1954). "EVALUATION OF CARBON DIOXIDE INHALATION THERAPY". American Journal of Psychiatry. 110 (10): 765–769. doi:10.1176/ajp.110.10.765.
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