Spinal Analgesia in Opioid-Dependent Patients
23. Why would spinal opioid analgesia still be appropriate if M.T. is opioid dependent?
Previous opioid use has minimal influence on epidural doses. Opioid-dependent patients can achieve adequate analgesia from epidural opioids, but their physical opioid dependency will not be satisfied. In fact, despite adequate analgesia, an opioid-dependent patient may exhibit symptoms of opiate withdrawal. These include restlessness, insomnia, nervousness, irritability, sweating, and GI hypermotility (nausea, emesis, and diarrhea). If withdrawal symptoms occur, they can be treated effectively by systemic administration of morphine or other opioids. Without treatment, such symptoms may persist for a few days. The dose of the systemic opioids varies with the patient's previous level of opioid dependence, and doses need to be adjusted accordingly. It would be appropriate to start M.T. on a short-acting opioid, such as meperidine 10 mg IV every 15 to 20 minutes, until the symptoms of withdrawal subside. This may be somewhat hazardous because the incidence of respiratory depression in the first 24 hours may be increased when opioids are administered by simultaneous epidural and systemic routes.93 Therefore, longer-acting opioids, such as methadone or levorphanol, should be avoided. The respiratory depression can be treated with the opioid antagonist naloxone, but the dose must be limited to 0.1 mg increments given IV to avoid precipitation of an acute withdrawal syndrome and reversal of analgesia. The naloxone dose can be repeated and the dose titrated to the desired clinical response.
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