Action of toxic doses of Local anesthesia on CNS can be described as
**Core Concept**
Toxic doses of local anesthetics can cause central nervous system (CNS) effects due to their ability to block sodium channels in the nervous system, leading to an accumulation of local anesthetic molecules in the brain.
**Why the Correct Answer is Right**
When local anesthetics reach toxic concentrations, they can penetrate the blood-brain barrier and bind to sodium channels in the CNS, leading to a blockade of sodium influx and subsequent hyperpolarization of neurons. This can result in symptoms such as confusion, seizures, and even coma. The most common local anesthetic associated with CNS toxicity is lidocaine, which binds to the sodium channel at the site of the inactivation gate, preventing the channel from returning to its resting state.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the mechanism of CNS toxicity caused by toxic doses of local anesthetics.
* **Option B:** This option is incorrect because it does not specify the sodium channel as the target of local anesthetic toxicity.
* **Option C:** This option is incorrect because it implies that the mechanism of CNS toxicity is due to the local anesthetic's effect on the blood-brain barrier, rather than its interaction with sodium channels.
**Clinical Pearl / High-Yield Fact**
To remember the mechanism of local anesthetic toxicity, use the mnemonic "SIDS": Sodium channel blockade, Inhibition of sodium influx, Depolarization, and Seizures.
**Correct Answer: C. Sodium channel blockade, Inhibition of sodium influx, Depolarization, and Seizures.**