Which one of the following is the fastest acting inhalational agent:
**Core Concept**
Inhalational anesthetics are a class of volatile compounds used for inducing and maintaining general anesthesia. Their potency and onset of action are influenced by their solubility in blood and tissues, as well as their mechanism of action on the central nervous system.
**Why the Correct Answer is Right**
The fastest acting inhalational agent is Sevoflurane. This is due to its low blood/gas partition coefficient (0.69), which allows for rapid uptake and distribution to the brain, resulting in a quick onset of anesthesia. Sevoflurane also has a pleasant odor and is well-tolerated by patients.
**Why Each Wrong Option is Incorrect**
**Option A:** Isoflurane has a higher blood/gas partition coefficient (1.46) compared to Sevoflurane, making it slower acting.
**Option B:** Desflurane has a low blood/gas partition coefficient (0.42), but its pungent odor and potential for airway irritation make it less suitable for rapid induction.
**Option C:** Halothane is an older inhalational agent with a higher blood/gas partition coefficient (2.4) and a slower onset of action compared to Sevoflurane.
**Clinical Pearl / High-Yield Fact**
Sevoflurane is often used for inhalational induction in pediatric patients due to its mild odor and non-irritating properties.
**Correct Answer: C. Sevoflurane**