Side-effects of epidural infusions of opioid bupivacaine mixtures

The incidence of side-effects occurring with epidural diamorphine (0.05 mg.ml-1), fentanyl (2.0 micrograms.ml-1), methadone (0.1 mg.ml-1), morphine (0.05 mg.ml-1) and pethidine (1.0 mg.ml-1) used by infusion in combination with bupivacaine has been compared. One hundred and sixty patients were studied, 32 receiving each opioid. The incidence of nausea and vomiting was significantly greater with morphine than fentanyl (p = 0.0097) and pethidine (p = 0.0021). The incidence of pruritus was significantly greater with morphine and diamorphine than with methadone (p = 0.012) and pethidine (p = 0.027). Morphine was also associated with a significantly greater incidence of urinary retention than pethidine (p = 0.012) and methadone (p = 0.025).