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Pain Team Department of Anaesthesia and Intensive Care Prince of Wales Hospital Protocol of Epidural Morphine Infusion Epidural morphine infusion is recommended as an alternative to conventional epidural mixture of local anaesthetic (bupivacaine or ropivacaine) and fentanyl in acute postoperative analgesia in surgical wards if conventional epidural local anaesthetic and fentanyl infusion fails to provide adequate analgesia and either one of the following criteria is met: 1. Conventional epidural local anaesthetic and fentanyl infusion fails to provide adequate analgesia because of incomplete segment of neural blockade in relation to surgical wound. 2. Conventional epidural local anaesthetic and fentanyl infusion causes significant motor or sympathetic blockade and side effect, e.g. hypotension. Steps of Setting up Epidural Morphine: 1. Stop conventional epidural local anaesthetic and fentanyl infusion. 2. No parenteral opioid or other CNS depressant to be given except as ordered by APS. 3. Maintain iv access for 24 hr after last dose of epidural morphine. 4. Give morphine bolus 2mg (for age>=80 yrs) or 3mg (for age<80yrs) morphine in 5ml NS via epidural catheter. 5. Consider giving analgesic adjunct via other routes for the interim period before epidural morphine onset (about 30min-1hr). 6. Set up epidural morphine infusion w/ Abott APM-II pump or Graseby 9300 as indicated in supplement (A) 7. Start epidural morphine (0.009% morphine) infusion at 4-6ml/hr for thoracic or lumbar epidural catheters. Start at slower rate for thoracic epidural catheter. 8. In case of inadequate analgesia after 2 hrs, reassess patient and consider increasing epidural infusion rate 1-2ml/hr. For the interim period, consider giving adjunct analgesia. 9. Metoclopramide 10mg iv Q8h prn and piriton 10mg Q8hr prn as standing order if there is no contraindication. 10.In case of significant side effects (e.g. nausea, vomiting, pruritis, urinary retention), consider decrease rate of epidural morphine infusion by 50% and refer to supplement for details of management. 11.In case of respiratory depression, stop epidural morphine infusion and refer to supplement for emergency management. 12.Routine Acute Pain Service monitoring protocol in surgical ward. Pain observation (including RR and sedation score) q1h for 1st 24 hours. Pain observation should continue for 24hr after last dose of epidural morphine. 13.Case will be reviewed by APS team twice daily. Supplement (A) Regime of epidural morphine infusion using Abott APM-II pump or Graseby 9300: 1. Mix 45mg morphine (3 ampoules of 15mg morphine each) into the 500ml NS to obtain 0.009% morphine. 2. Final concentration: Morphine 0.009% Final volume 503ml (Please set the reservoir/ cassette volume to 495ml. This is to make sure that the pump will alarm before the medication bag runs out) 3. Label the medication bag using the green additive gum label. 4. Prescribe “epidural morphine protocol: 45mg morphine to a total NS 503ml” in prn drug chart. 5. Put down “on epidural morphine, no opioid/sedative unless prescribed by pain team” on drug charts. Supplement (B) Management of side effect of epidural morphine: 1. Nausea and vomiting: - incidence 12-50% - usually subsides with metoclopramide 10mg Q6-8h prn or ondansetron 4mg q8h prn. - Reduce epidural morphine infusion rate 2. Itchiness: - incidence: 30% - Treatment: - i. Diphenhydramine 10mg iv/ 3mg po q6-8h prn. Other alternatives include naloxone bolus 40ug and propofol bolus. - ii. Reduce epidural morphine infusion rate 3. Urinary retention: - incidence: 67% - usually not problematic since most acute postoperative patients on epidural morphine are on foley for monitoring in surgical ward. - Treatment: reduce epidural morphine infusion rate. May consider naloxone 40mcg bolus. 4. Somnolence: - Treatment: reduce epidural morphine infusion rate. 5. Respiratory depression: - early depression reflects systemic absorption - late depression reflects rostral migration of CSF - gradual in onset - usually within first 12 hrs - clinically significant respiratory depression 0.1%-0.4% - risk factors: large dose, large injectate volume, intermittent boluses, age over 60, coexisting respiratory diseases, debilitated, raised intrathoracic pressure, concommitent parenteral opioid, opioid naïve patients - Treatment: - i. ABC. - ii. Stop epidural infusion - iii naloxone 40mcg then infusion 5mcg/kg/hr (may precipitate acute opioid withdrawal) For further enquiry, please call pain nurse (6172) or pain MO (1067).
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