A patient receives a toxic dose of lignocaine i.v., the patient is likely to exhibit:
## **Core Concept**
Lignocaine (lidocaine) is a local anesthetic and antiarrhythmic drug that can cause systemic toxicity when administered in high doses, particularly intravenously. This toxicity primarily affects the central nervous system (CNS) and cardiovascular system. The CNS effects range from excitatory (e.g., agitation, seizures) to depressive (e.g., coma) manifestations.
## **Why the Correct Answer is Right**
The correct answer, , is associated with seizures or convulsions. Lignocaine toxicity initially causes CNS excitation, which can manifest as agitation, tremors, and eventually seizures. This occurs because lignocaine blocks sodium channels in the brain, leading to an initial phase of excitation. As toxicity worsens, it can progress to CNS depression. The mechanism involves the blockade of voltage-gated sodium channels, which are crucial for the initiation and propagation of action potentials in neurons.
## **Why Each Wrong Option is Incorrect**
- **Option A:** - This option does not directly relate to a common manifestation of lignocaine toxicity.
- **Option B:** - While lignocaine can affect the cardiovascular system by depressing myocardial contractility and causing vasodilation, leading to hypotension, this is not the most direct or commonly emphasized effect of acute toxicity.
- **Option C:** - Although lignocaine can cause respiratory depression or arrest in severe toxicity, this option does not specifically highlight a unique or initial presentation of lignocaine toxicity.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that early signs of lignocaine toxicity can include circumoral numbness, tongue paresthesia, and light-headedness. Severe toxicity can lead to seizures, which are a medical emergency. Treatment involves stopping the infusion, supportive care, and in severe cases, administration of lipid emulsion.
## **Correct Answer: D. seizures.**