Catheters are fine plastic tubes that are used to help anesthesiologists administer anesthesia and pain medications as a continuous infusion. These catheters are inserted near bundles of nerves to provide medications that can be used to treat post-operative pain. Local anesthetics are the usual medications that are used for catheter-treated post-operative pain. Ropivicaine is the most common local anesthetic administered through catheters. Catheters are usually placed in the pre-operative area before the start of surgery.