Epidural catheter analgesia for the management of postoperative pain.

Since its introduction to North America in 1942, the use of epidural catheter analgesia has increased dramatically. Improved equipment, methods and medications have broadened its application to include among others, surgical anesthesia, chronic pain relief and the management of postoperative pain. Numerous techniques for epidural puncture and insertion of the catheter have been described. Although complications have been associated with placement of an epidural catheter, these are rare when performed by an experienced anesthesiologist. Epidural analgesia was first accomplished by blockade with local anesthetics. Bupivacaine has been called the local anesthetic of choice for epidural infusion. Bolus administration of epidural local anesthetics gives effective analgesia; however, its use is limited by brief duration and occasionally severe hypotension. Epidural local anesthetics have been administered by continuous infusion in an attempt to minimize side effects. Nevertheless, hypotension, as well as motor block, numbness, nausea and urinary retention have occurred. Epidural analgesia with local anesthetics is effective in relieving postoperative pain, but its safety and feasibility have been questioned because of the frequent, potentially serious side effects. These problems led to trials of epidural narcotics for postoperative pain management. The exact site of action of epidural narcotic analgesics is debatable; however, the bulk of evidence supports a direct spinal action. Epidural narcotics appear to specifically inhibit nociceptive stimuli. The prolonged and profound analgesia that occurs with epidural narcotics relative to parenteral administration is due to a higher concentration of drug reaching the CSF through the epidural route. Since nervous transmission is not completely blocked this technique cannot provide anesthesia during operation. Morphine has been the most frequently used narcotic for epidural analgesia. Results of several recent, randomized double-blind studies have shown that epidural narcotics give adequate analgesia comparable with that observed with epidural bupivacaine. Epidural morphine provides a greater duration of analgesia and may cause fewer side effects. Improved analgesia has been reported when epidural narcotics are used in combination with local anesthetics. Continuous administration of low dosage epidural narcotics has been shown to have less frequent side effects than bolus administration. Nevertheless, pruritus, urinary retention, hypotension and severe respiratory depression have been reported with both methods.(ABSTRACT TRUNCATED AT 400 WORDS)