Postcesarean epidural morphine: A dose-response study

The purpose of this study was to describe the dose-response relationship of epidural morphine for postcesarean analgesia for quality of analgesia and relation to the side effects of pruritus, nausea, and vomiting. Sixty term parturients undergoing nonurgent cesarean delivery were enrolled and random ized to receive a single dose of epidural morphine after delivery (0,1.25, 2.5, 3.75, or 5 mg). A patient-controlled analgesia (PCA) device provided f ree access to additional analgesics. PCA morphine use and the incidence and severity of side effects were recorded for 24 h. Data were analyzed with a nalysis of variance, Student's t-tests, and chi(2) analysis. Nonlinear regr ession was used to describe a dose-response curve. PCA use differed signifi cantly among groups (P < 0.001); PCA use was significantly greater in Group 0 mg than Groups 2.5, 3.75, and 5 mg (P < 0.05). PCA use was also signific antly greater in Group 1.25 mg than Groups 3.75 and 5 mg (P < 0.05). Prurit us scores were significantly higher in all groups given epidural morphine t han the control group (0 mg) (P < 0.05), but did not differ among the treat ment groups (1.25-5 mg), although pruritus scores were significantly higher in treatment groups than in the control (P < 0.05). No relation was found between epidural morphine dose and incidence or severity of nausea and vomi ting. We concluded that, for optimal analgesia, augmentation of epidural mo rphine with systemic analgesics or other epidural medications may be necess ary. Implications: Quality of analgesia increases as the dose of epidural m orphine increases to at least 3.75 mg; increasing the dose further to 5 mg did not improve analgesia. Side effects were not dose related. For optimal analgesia, augmentation of epidural morphine with systemic analgesics or ot her epidural medications may be necessary.