Using a Local Anesthetic

For total or partial knee replacements, the anesthesiologist may offer you a peripheral nerve block. A peripheral nerve block is a blockage of pain signals from a nerve to the brain, creating a numb area. This is accomplished by surrounding the nerve with a local anesthetic.


What are the benefits associated with a peripheral nerve block?

A peripheral nerve block provides superior pain relief to oral or intravenous pain medicines alone. We find that adding a peripheral nerve block to the oral or intravenous pain medicines allows people to participate in physical therapy better and that they need less of the morphine-type pain medicines. Since the morphine-type pain medicines can make you groggy, nauseated, constipated, and itchy, we think needing less of them is better.

How is a peripheral nerve block performed?

The anesthesiologist will identify the nerve using ultrasound. Next they will clean off your skin with sterile solution. A small amount of local anesthetic is injected to numb the skin, and a needle is guided under ultrasound to a location near but not touching the nerve. The local anesthetic is then injected near the nerve.

How long will it take to get numb?

You may notice pain relief within 5-10 minutes. Full effect may take up to 30 minutes or longer.

How Long Does a Peripheral Nerve Block Last?

It is different for each individual. If a single injection of local anesthetic is performed, you will be numb for 12-36 hours. If a nerve catheter is placed, you will be numb for two days.

What's a nerve catheter?

A nerve catheter is a thin piece of flexible plastic tubing that is placed under the skin near the nerve. It is fastened to the skin with a bandage and connected to a plastic pump about the size of a baby bottle. The pump will inject local anesthetic for about two days.

How do I take care of a nerve catheter?

Just don’t pull the bandage off! When it’s time to remove the nerve catheter (you’ll know it’s time because the balloon inside the bottle will be empty), remove the bandage, and the catheter. If the catheter doesn’t come out easily, come back to the hospital and we will remove it for you.

What are the side effects of a peripheral nerve block?

Your leg will be numb and weak. You must follow your anesthesia doctor's instructions regarding walking on your leg while it is numb. Please be aware of where your leg is at all times, as your leg could be injured without your knowledge (by stubbing your toe, for example). If you step on your leg when you have been advised not to, you may fall.

What are the risks associated with a peripheral nerve block?

The three major risks of a nerve block are infection, bleeding, and nerve damage. These are all extremely rare complications. However, if you already have numbness or tingling in your leg or foot, please let the anesthesiologist know. A nerve block may be more likely to cause nerve damage if you already have these symptoms.

Do I still need to go to sleep for my surgery?

Typically, you will either go to sleep with a general anesthesia or have a spinal anesthesia with makes you numb from your chest to your feet. However, if there is an important reason not to use a spinal or a general anesthesia, some surgeries can be performed with a nerve block. You will have the opportunity to discuss this with your anesthesiologist.