Epidural morphine: a clinical double-blind study of dosage

Anesth Analg. 1985 Aug;64(8):786-91.


The purpose of this randomized double-blind study was to determine the optimal dose of epidural morphine by establishing a dose-effect relationship. The 139 patients, who had orthopedic operations on the lower extremities, received continuous lumbar epidural anesthesia with bupivacaine, 0.75%, with or without the addition of 1, 2, 3, 4, or 5 mg of morphine hydrochloride. Analgesia and side effects were determined during the first 24 hr postoperatively. In the 12-hr period after epidural anesthesia, arterial blood gas tensions were compared between those patients who received 5 mg morphine (n = 13) and those who received no morphine (n = 14). Patients who received 2 or more mg of morphine were less likely to require the administration of postoperative systemic analgesics (P less than 0.05). The addition of 2 or more mg of morphine to bupivacaine, 0.75%, reduced postoperative pain intensity (P less than 0.05); 5 mg of morphine reduced pain intensity for the longest time. Frequency of catheterization and pruritus increased dose-dependently. The mean PaCO2 after 5 mg of epidural morphine averaged 5 mm Hg higher than in the control group, indicating minor respiratory depression, better analgesia, or both. The dose of 3 mg of epidural morphine added to the local anesthetic is recommended for postoperative analgesia after surgery of the lower extremity; it is a compromise that provides adequate analgesia with an acceptably low frequency and intensity of side effects.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Analgesics / administration & dosage
  • Anesthesia, Epidural
  • Blood Gas Analysis
  • Bupivacaine / administration & dosage
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Female
  • Humans
  • Leg / surgery
  • Male
  • Middle Aged
  • Morphine / administration & dosage*
  • Morphine / adverse effects
  • Morphine / therapeutic use
  • Pain, Postoperative / drug therapy*
  • Pruritus / chemically induced
  • Random Allocation
  • Time Factors
  • Urination / drug effects


  • Analgesics
  • Morphine
  • Bupivacaine