Intrathecal diamorphine for analgesia after caesarean section. A dose finding study and assessment of side-effects

Eighty women undergoing elective Caesarean section under spinal anaesthesia using hyperbaric bupivacaine 0.5% were randomly allocated to receive, in addition, intrathecal diamorphine 0.125, 0.25 or 0.375 mg or saline. Postoperative morphine requirements, measured using a patient-controlled analgesia system, were reduced in a dose-dependent manner by diamorphine. Pain scores were significantly lower at 2 and 6 h following the two larger doses of diamorphine. Less supplemental analgesia was required intra-operatively if intrathecal diamorphine had been given. The incidences of vomiting and pruritus were also dose-related. No respiratory rates of less than 14 breath.min-1 were recorded and the incidence of oxygen saturation readings less than 95% and 90% did not differ between groups. There were no adverse neonatal effects. Intrathecal diamorphine in the present study was found to be safe in doses of up to 0.375 mg following Caesarean section. However, minor side-effects were frequently observed.