What event may cause an electric shock during the delivery of local anesthesia?

• A. Needle touched the nerve sheath
• B. The needle overheated
• C. The patient moved suddenly
• D. The anesthetic expired

Answer: (A)

When using a nerve stimulator to guide local anesthesia, an electric shock is most likely to occur if the needle tip touches or penetrates a nerve sheath. This creates a direct path for the electrical current to reach the nerve fibers, producing a sudden, sharp shock sensation in the distribution of the nerve. This sharp feedback is a warning sign that the needle is intraneural or very close to neural tissue, so the clinician should reposition to achieve a safer, perineural or extra-neural injection. Other scenarios, like the needle overheating, the patient moving, or the anesthetic expiring, do not produce the characteristic electric shock. The key takeaway is that a nerve-contacting needle with a stimulator commonly causes that sensory shock.