[Secondary effects of opioids administered by the regional route]

The administration of narcotics in the subarachnoid or the epidural space is gaining acceptance for postoperative pain relief. However, the potential side effects of intrathecal and epidural use of opioids are the following: early and late respiratory depression, pruritus, nausea and vomiting, urinary retention. Early respiratory depression is low and may occur 6 or 12 hours after the epidural narcotics injection. Many factors contribute to the delayed phase of breathing disorders and a close respiratory monitoring is needed during at least 24 hours after epidural morphine injection. Naloxone can be used to reverse the depression. Pruritus can occur in 10 to 30% of patients receiving morphine; 10 to 30% nausea and vomiting, and urinary retention occurs in 20 to 50% of patients.