Potentiation of opioid analgesia can be achieved by the addition of midazolam intrathecally. At our institution, analgesia following open abdominal surgery is provided by continuous infusion of analgesic solutions either intravenously, intrathecally (incorporating midazolam) or epidurally. We report the results of a study comparing outcomes with these three analgesic regimens following major open abdominal surgery. This was an unblinded prospective audit of pain service intervention rates, pain scores and other outcomes after intravenous, intrathecal and epidural analgesia after open abdominal surgery in patients over 60 years of age. Both elective and emergency cases were included over a nine-month period. Patients ventilated for 24 hours or more were excluded. The analgesic regimens were as follows:
1. Intravenous: patient controlled analgesia with morphine + ketamine infusion 0.1 to 0.2 mg/kg/h.
2. Intrathecal: (morphine 10 µg/ml + midazolam 100 µg/ml + bupivacaine 0.05%) commenced at 2 ml/h.
3. Epidural: bupivacaine 0.125% + fentanyl 2 µg/ml at 6 to 14 ml/h.
Co-analgesic administration was as per our usual practice but was not standardised. The median number of calls per patient to the pain service differed between the intravenous (1), intrathecal (1) and epidural (3) groups. The number of unintentional analgesic regimen terminations differed between the intravenous (1), intrathecal (1) and epidural (5) groups. Pain scores differed significantly between groups and were lowest in the intrathecal group at all time points. The findings indicate that the intrathecal group had both a low requirement for postoperative interventions/resources and excellent analgesia. It appears to be a suitable alternative to the other techniques.