Second gas effect


In theory second gas effect phenomenon should speed the onset of anesthetic induction. Because nitrous oxide is insoluble in blood, its rapid absorption from alveoli results in an abrupt rise in the alveolar concentration of the accompanying volatile anesthetic. However, even at high concentrations (70%) of nitrous oxide, this effect accounts for only a small increase in concentration of volatile anesthetic. Recent studies have had conflicting results as to whether this phenomenon is valid. When nitrous oxide is discontinued abruptly, its rapid diffusion from the blood to the alveolus decreases the oxygen tension in the lung, leading to a brief period of decreased oxygen concentration known as diffusion hypoxia. Administering 100% oxygen at the end of a case can mitigate this.

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