Least MAC is of which inhalational agent?
**Core Concept**
Inhalational anesthetics are a class of volatile liquids that induce and maintain general anesthesia when administered via inhalation. Minimum Alveolar Concentration (MAC) is a measure of anesthetic potency, defined as the concentration of anesthetic in the lungs required to prevent movement in 50% of patients in response to a painful stimulus. A lower MAC value indicates a more potent anesthetic.
**Why the Correct Answer is Right**
The MAC value of an inhalational agent is inversely related to its potency. Agents with lower MAC values are more potent and require lower concentrations to achieve the same level of anesthesia. This is because they have a higher affinity for the target receptor, which is usually the GABA receptor in the central nervous system. The agent with the lowest MAC value among the options is Desflurane, which has a MAC value of 6%. This is because Desflurane has a high blood/gas partition coefficient, which allows it to quickly achieve and maintain a high concentration in the lungs.
**Why Each Wrong Option is Incorrect**
**Option A:** Isoflurane has a MAC value of 1.17%, making it less potent than Desflurane.
**Option B:** Sevoflurane has a MAC value of 2%, making it less potent than Desflurane as well.
**Option C:** This option is missing.
**Clinical Pearl / High-Yield Fact**
Remember that the MAC value of an inhalational agent is not the only factor that determines its potency. Other factors, such as blood/gas partition coefficient and solubility in blood, also play a significant role in determining the anesthetic's potency and onset time.
**Correct Answer: D. Desflurane**