What is Continuous Epidural Infusion?
In Continuous Epidural Infusion a small tube is placed in the back. This tube is positioned in the epidural space, outside the layer of tissue that protects the spinal cord. Attached to the tube is a computer-controlled pump which delivers a steady amount of medication. The medication contains a local anesthetic and a narcotic. These medications "bathe" the nerves that pass through the epidural space. Because these are nerves that transmit sensation, the drugs block pain as well as heat, cold and pressure. Epidurals are most commonly associated with childbirth, and are utilized to lessen the pain associated with labor.
For pain after hip, abdominal, or thoracic surgery, a continuous epidural infusion is often selected, especially for medically high-risk patients. Infusion of bupivacaine 0.0625% to 0.125% with fentanyl 2 to 4 µg/mL at 8 to 10 mL/hour usually relieves pain, but upward titration may be needed. Ropivacaine, a relatively new local anesthetic, has less cardiovascular toxicity and is used in the same concentrations as bupivacaine.
Insertion of an epidural catheter at the site of perceived discomfort can reduce the amount of local anesthetic and opioid needed, minimizing the possibility of toxicity. For hip surgery, the catheter is inserted in the lumbar region; for abdominal surgery, the lower thoracic region; and for thoracotomy, the midthoracic region. Fentanyl is lipophilic and does not spread widely in the epidural space, so the catheter must be placed near the nerve source of the pain. Epidural morphine spreads more readily; however, the forward spread of morphine may cause late respiratory depression.