According to Journal of Anesthesia (1994, 1995, 1996), Journal of Japan Society for Clinical anesthesia (1993, 1994, 1995) and Journal of Japan Society of Pain Clinicians (1994, 1995, 1996), there were 125 postoperative pain control reports following thoracotomy and intraabdominal surgery. Epidural analgesia was applied to 115 reports (92%) of 125 reports. Continuous epidural infusion of local anesthetics and opioids by balloon type infuser were commonly used. Bupivacaine 0.25-0.5% solution was a main local anesthetics for postoperative use. Common continuous epidural infusion rates were 1-2ml/h. Morphine (4.7±0.5mg/day), fentanyl (0.45±0.15mg/day) and buprenorphine (0.35±0.15mg/day) were 3 main opioids administered epidurally. There was few reports associated with respiratory depression in these reports.
However, respiratory depression following epidural opioids is unpredictable and may be associated with any opioid. It is clear that there is no opioid that is unequivocally safer than morphine for epidural use. Slow infusion should be safer than large intermittent epidural injections. Monitoring of the level of consciousness and counting of the respiratory rate are important. Other complications from administration of epidural opioid include pruritus, nausea, and urinary retention. Because of slow onset of epidural morphine analgesia, it is recommended that primary dose of epidural morphine is administered before surgery and then start continuous epidural infusion during surgery. That is useful to shorten the time of respiratory monitoring.
