title: Time-related differential effects of epidural morphine on the neuraxis.
abstract: To clarify the site and potency of the analgesic and anesthetic action of epidurally administered morphine, we investigated the effects of epidurally and intravenously administered morphine (100 micrograms/kg) on change in the pressure pain threshold (PPT) and the minimum alveolar concentration (MAC) of halothane. Epidural morphine (EM) increased PPT significantly (P < 0.01) at the points around the surgical incision by 40% and 60% from baseline compared with intravenous morphine (IM) with which PPT remained at baseline 1 and 2 h after administration, respectively. Duration of analgesia was much longer in EM than in IM (18 h vs 1.7 h). EM increased PPT from preoperative value at the forehead and the points around the surgical incision by 9.9% and -24.9% at 1 h, by 10.9% and 3.8% at 4 h, and by -19.5% and -50.4% at 12 h after administration at mean values, respectively. Halothane MAC in EM and IM were 0.54% and 0.57%, respectively, 40 min after administration. Halothane MAC in EM at 4 h and 12 h after administration were 0.45% and 0.70%, respectively. The results suggest that EM provides long-lasting analgesia by its time-related differential effects on the neuraxis.
authors.affiliation: Department of Anesthesiology, Osaka University Medical School, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Inagaki
authors.forename: T
authors.initials: T
authors.lastname: Mashimo
authors.forename: I
authors.initials: I
authors.lastname: Yoshiya
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural; D000767:Anesthesia, Epidural; D000769:Anesthesia, Inhalation; D005260:Female; D005743:Gastrectomy; D006221:Halothane; D006801:Humans; D008297:Male; D008875:Middle Aged; D009020:Morphine; D017288:Pain Threshold / Q000187:drug effects*; D011312:Pressure; D011446:Prospective Studies; D013997:Time Factors
chemical_list: D009020:Morphine; D006221:Halothane