A double-blind assessment of the analgesic sparing effect of intrathecal diamorphine (0.3 mg) with spinal anaesthesia for elective caesarean section

In a randomized double-blind study, 40 healthy women undergoing elective caesarean section with spinal anaesthesia received either 0.3 mg diamorphine or saline with bupivacaine 0.5% in 8% dextrose. The study recorded time to the first morphine demand delivered by patient-controlled analgesia (PCA), and total morphine requirement over 24 h. In addition pain, sedation, and pruritus were assessed by non-graduated visual analogue scores (VAS). Six patients in the diamorphine group required no postoperative morphine. The median (interquartile range) time to first morphine demand was significantly longer in the diamorphine group at 340 min (127, never used), than in the control group at 80 min (53, 159) (P 0.0006, 95% confidence interval for the difference between the medians is 60 to 1235 min). The use of PCA morphine over 24 h was significantly less in the diamorphine group than in the controls. The medians (interquartile ranges) were 5 (0, 36) mg vs 45 (26, 72) mg (P 0.0045, 95% confidence interval for the difference between the medians is 12 to 46 mg). In the diamorphine group, postoperative VAS for pain was significantly lower at 2 h and 3 h both at rest (P 0.0003, 0.003) and on moving (P 0.009, 0.002), at 8 h on moving (P 0.01), and at 12 and 24 h at rest (P 0.005, 0.029). Significantly more women suffered pruritus in the diamorphine group for the first 12 h after surgery (P 0.01).