This depends on the type of block performed and the type of numbing medication used. For example, nerve blocks for hand surgery usually last for 6-8 hours, but a nerve block for pain after total knee replacement can last for 12-24 hours. Medication continuously delivered through a tiny plastic tube (nerve catheter) placed next to the nerve can last for 2-3 days.

This usually happens when the body develops drug tolerance. Tolerance is a normal physiological response to narcotics and occurs when the initial dose of a substance loses its effectiveness over time. Changing the dose or the medication often solves the problem. Just because you have become tolerant of a drug does not mean that you are addicted to that drug.

You will need to avoid solid foods for several hours before going under anesthesia, but you can usually drink clear fluids. Make sure you follow your doctor’s instructions about eating and drinking before your procedure very carefully to prevent any problems. Your doctor may also ask you to avoid taking certain medications.