Which among the following anaesthetic increases the cerebral oxygen consumption?
**Core Concept**
The cerebral metabolic rate for oxygen (CMRO2) is a critical factor in determining the adequacy of cerebral oxygen supply during anesthesia. Factors that increase CMRO2 can lead to increased cerebral oxygen consumption, which may be detrimental in certain clinical scenarios.
**Why the Correct Answer is Right**
Isoflurane is a volatile anesthetic agent that increases CMRO2 by stimulating the mitochondrial electron transport chain, thereby increasing the production of adenosine triphosphate (ATP). This effect is thought to be mediated by the activation of the sodium-potassium ATPase pump, which increases the energy demand of brain cells. As a result, isoflurane increases cerebral oxygen consumption, which may be a concern in patients with compromised cerebral oxygen delivery.
**Why Each Wrong Option is Incorrect**
* **Option A:** Halothane is a volatile anesthetic agent that decreases CMRO2 by reducing the activity of the mitochondrial electron transport chain. This effect is thought to be mediated by the activation of potassium channels, which decreases the energy demand of brain cells.
* **Option B:** Propofol is a non-volatile anesthetic agent that decreases CMRO2 by reducing the activity of the sodium-potassium ATPase pump. This effect is thought to be mediated by the activation of GABA receptors, which decreases the energy demand of brain cells.
* **Option D:** Ketamine is a non-volatile anesthetic agent that has a complex effect on CMRO2. While it may increase CMRO2 in some scenarios, its overall effect is thought to be neutral or even decreasing in many clinical situations.
**Clinical Pearl / High-Yield Fact**
When choosing an anesthetic agent, it's essential to consider the potential effects on cerebral oxygen consumption, particularly in patients with compromised cerebral oxygen delivery. Isoflurane and other volatile anesthetic agents may increase CMRO2, while non-volatile agents like propofol may decrease it.
**Correct Answer:** C. Isoflurane