Second gas effect
During induction of general anesthesia, when a large volume of a gas (e.g. nitrous oxide) is taken up from alveoli into pulmonary capillary blood, the concentration of gases remaining in the alveoli is increased. This results in effects known as the second gas effect[1] and the "concentration effect". These effects occur because of the contraction of alveolar volume associated with the uptake of the nitrous oxide. Previous explanations by Edmond I. Eger and Robert K. Stoelting have appealed to an extra-inspired tidal volume due to a potential negative intrapulmonary pressure associated with the uptake of the nitrous oxide.[2]
There are two extreme breathing patterns and the extra-inspired tidal volume is an artificial construct associated with one of these patterns.[3] Thus it is the volume change that actually causes the effects.[citation needed]
An applicable example from Stedman's medical dictionary
[edit]When a constant concentration of an anesthetic such as halothane is inspired, the increase in alveolar concentration is accelerated by concomitant administration of nitrous oxide, because alveolar uptake of the latter creates a potential subatmospheric intrapulmonary pressure that leads to increased tracheal inflow.
See also
[edit]References
[edit]- ^ Epstein, R.M.; Rackow,H.; Salanitre,E.; Wolf,G.L. (1964). "Influence of the Concentration Effect on the Uptake of Anesthetic Mixtures: The Second Gas Effect". Anesthesiology. 25 (3): 364–371. doi:10.1097/00000542-196405000-00015. PMID 14156577.
- ^ Stoelting, R.K.; Eger,E.I. (1969). "An Additional Explanation for the Second Gas Effect: A Concentrating Effect". Anesthesiology. 30 (3): 273–277. doi:10.1097/00000542-196903000-00007. PMID 5778096.
- ^ Korman, B.; Mapleson, W. W. (May 1997). "Concentration and second gas effects: can the accepted explanation be improved?". British Journal of Anaesthesia. 78 (5): 618–625. doi:10.1093/bja/78.5.618. PMID 9175984.
- Mapleson, W. W.; Korman, B. (Dec 1998). "Concentration and second-gas effects in the water analogue". British Journal of Anaesthesia. 81 (6): 837–843. doi:10.1093/bja/81.6.837. PMID 10211005.
- Errata British Journal of Anaesthesia 1997;79:268
