**Core Concept**
Intravenous regional anesthesia (IVRA), also known as Bier block, involves injecting a local anesthetic into a limb while it is isolated from the rest of the body. The choice of local anesthetic is crucial to ensure patient safety and effective anesthesia.

**Why the Correct Answer is Right**
Bupivacaine should not be used for IVRA due to its high potential for toxicity, particularly cardiovascular toxicity. Bupivacaine has a high lipid solubility, which allows it to easily cross the blood-brain barrier and cause central nervous system toxicity. Additionally, bupivacaine has a long duration of action, which increases the risk of toxicity if the tourniquet is released prematurely. This makes bupivacaine a high-risk choice for IVRA.

**Why Each Wrong Option is Incorrect**
**Option A:** Lignocaine is a commonly used local anesthetic for IVRA due to its moderate potency, rapid onset, and relatively low toxicity profile.
**Option C:** Prilocaine is another suitable option for IVRA, with a lower potential for toxicity compared to bupivacaine and a relatively fast onset of action.
**Option D:** Lignocaine + ketorolac is a combination that can be used for IVRA, as ketorolac is an NSAID that can provide analgesia without adding to the risk of local anesthetic toxicity.

**Clinical Pearl / High-Yield Fact**
When choosing a local anesthetic for IVRA, it's essential to consider the patient's overall health, the type of surgery, and the potential risks and benefits of each anesthetic. Always use a local anesthetic with a moderate to low potential for toxicity, and never use bupivacaine for IVRA.

**✓ Correct Answer: B. Bupivacaine**