Morphine neuraxial

Therapeutic doses of the opioid analgesics produce flushing and warming of the skin accompanied sometimes by sweating and itching CNS effects and peripheral histamine release may be responsible for these reactions. Opioid-induced pruritus and occasionally urticaria appear more frequently when opioid analgesics are administered parenterally. In addition, when opioids such as morphine are administered to the neuraxis by the spinal or epidural route, their usefulness may be limited by intense pruritus over the lips and torso. 

Opioids potentiate the analgesic effect of neuraxial local anesthetics, with minimal adverse effects (SEDA-18,141) (SEDA-20, 121) (SEDA-22, 135), as shown in several studies with clonidine, fentanyl, morphine, or pethidine as the systemic or neuraxial analgesic, and bupivacaine, lidocaine, and ropivacaine as the local anesthetic. The benefits have been shown in relief of long-term pain and postoperative pain, in adults and children (SEDA-18, 141) (SEDA-18,146). 

Caranza R, Jeyapalan I, Buggy DJ. Central neuraxial opioid analgesia after caesarean section comparison of epidural diamorphine and intrathecal morphine. Int J Obstet Anesth 1999 8(2) 9(>-3. 

Peptide transmitters Many peptides have been identified in the CNS, and some meet most or all of the criteria for acceptance as neurotransmitters. The best-defined ones are the opioid peptides (beta-endorphin, met- and leu-enkephalin, and dynorphin), which are distributed at all levels of the neuraxis. Some of the important therapeutic actions of opioid analgesics (eg, morphine) are mediated by receptors for these endogenous peptides. Substance P is localized in type C neurons involved in nociceptive sensory pathways in the spinal cord. Peptide transmitters differ from nonpeptide transmitters in that (1) the peptides are synthesized in the cell body and transported to the nerve ending via axonal transport, and (2) no reuptake or specific enzyme mechanisms have been identified for terminating their actions. 

Cesarean delivery morphine is currently the gold-standard neuraxial opioid for post-cesarean analgesia. It provides effective post-operative analgesia for 12-24 h. 

Use in biliary surgery or disorders of the biliary tract as significant morphine is released into the systemic circulation from neuraxial administration, the ensuing smooth muscle hypertonicity may result in biliary colic. 

Use in ambidatory patients patients with reduced circidating blood volume, impaired myocardial function or on sympatholytic drugs should be monitored for the possible occmrence of orthostatic hypotension, a frequent complication in single-dose neuraxial morphine analgesia Epidmal morphine should not be given to outpatient singical patients. 

Use with other central nervous system depressants the depressant effects of morphine are potentiated by the presence of other CNS depressants such as alcohol, sedatives, antihistaminics or psychotropic drugs. Use of neuroleptics in conjimction with neuraxial morphine may increase the risk of respiratory depression. 

Preservative-free Duramorph (morphine sulfate injection, USP) is a sterile, nonpyrogenic, isobaric solution of morphine sulfate, free of antioxidants, preservatives or other potentially neurotoxic additives. Selective blockade of pain sensation is possible by neuraxial application of morphine and duration of analgesia may be much longer by this route compared to systemic administration. 

Intravenous access should he maintained for 24 h after administration of epidural morphine. Whether the addition of parenteral opioids or hypnotics to neuraxial opioids is associated with increased occurrence of respiratory depression or hypoxemia is unclear. 

Common adverse events sedation, respiratory depression, pruritus, nausea/vomiting, constipation, and urinary retention, which are treated with a naloxone 40-80 pg IV bolus followed by an infusion of 50-100 pg/h. However, these adverse events are relatively less commonly observed with epidural hydromorphone than with neuraxial morphine regimens. Pruritus is treated with a naloxone infusion of 50-100 pg/h, diphenhydramine 12.5-50 mg or propofol infusion of 10 mg/h. Nausea and vomiting is best treated with either ondansetron (4-8 mg IV), low-dose droperidol (0.625-1.25 mg IV), metoclopramide (10 mg IV every 4-6 h), or transdermal scopolamine patch during the first 10 hours following administration. 

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