A comparison of morphine concentrations for patient-controlled epidural analgesia following gynecological surgery

To compare the analgesic efficacy of a lower (12.5 mg/mL) vs. higher (25 mg/mL) concentration of morphine with 0.2% ropivacaine for patient-controlled epidural analgesia (PCEA) following gynecological surgery.

In a randomized double-blinded study, 40 ASA physical status I and II gynecological patients who were receiving combined general and epidural anesthesia for surgery and epidural analgesia for postoperative analgesia were assigned to receive 12.5 mg/mL (N=20) or 25 mg/mL (N=20) morphine with 0.2% ropivacaine for PCEA (continuous infusion 4 mL/h, bolus injection 2 ml, lockout interval 15 min). Maximum visual analogue pain scores (VAPS) at rest (VAPS-R max) and movement (VAPS-M max) during the previous 24 hours were assessed at 24 and 48 hours postoperatively, and the cumulative number of self-administrations in PCEA during the postoperative 48 h were also measured.

There were no significant differences in VAPS at rest or with movement, and there were no differences in the cumulative boluses of PCEA between the groups. The incidences of nausea, vomiting, pruritus and leg numbness were greater in the 25 mg/mL morphine group, although statistically insignificant.

PCEA using 0.2% ropivacaine and 12.5 mg/mL morphine compared with 0.2% ropivacaine and 25 mg/mL morphine provides equianalgesia with no differences in bolus administration. With respect to the analgesic efficacy and the potential risk for side effects, PCEA using 0.2% ropivacaine and 12.5 mg/ml morphine is a better choice for postoperative gynecological patients.