Second gas effect

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title: "Second gas effect" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["anesthesia"] description: "Effect occurring during general anesthesia" topic_path: "general/anesthesia" source: "https://en.wikipedia.org/wiki/Second_gas_effect" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Effect occurring during general anesthesia ::

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 |last=Epstein |first=R.M. |author2=Rackow,H. |author3=Salanitre,E. |author4=Wolf,G.L. |title=Influence of the Concentration Effect on the Uptake of Anesthetic Mixtures: The Second Gas Effect |journal=Anesthesiology |date=1964 |volume=25 |issue=3 |pages=364–371 |doi=10.1097/00000542-196405000-00015 |pmid=14156577 |doi-access=free}} 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. |last=Stoelting |first=R.K. |author2=Eger,E.I. |title=An Additional Explanation for the Second Gas Effect: A Concentrating Effect |journal=Anesthesiology |date=1969 |volume=30 |issue=3 |pages=273–277 |doi=10.1097/00000542-196903000-00007 |pmid=5778096 |doi-access=free}}

There are two extreme breathing patterns and the extra-inspired tidal volume is an artificial construct associated with one of these patterns.

• Errata British Journal of Anaesthesia 1997;79:268 Thus it is the volume change that actually causes the effects.

Examples

An applicable example from Stedman's medical dictionary is 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.

References

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::