Second Gas Effect Clinical — FRCA Primary MCQ

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ModeratePharmacology - Inhalational AgentsSecond Gas Effect ClinicalFRCA Primary

The second gas effect explains why adding 70% N2O to a volatile agent:

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Correct answer: E — Accelerates the rise of the volatile agent's alveolar concentration

The rapid uptake of large volumes of N2O from the alveoli concentrates the remaining gases (concentration effect on the second agent) and draws additional gas into the alveolus (augmented inflow). Both mechanisms accelerate the rise of FA/FI of the second volatile agent during co-administration with N2O.

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care