Pre-emptive analgesia with epidural morphine or morphine and bupivacaine

Studies of pre-emptive analgesia in humans have shown conflicting results. The study design, patient population and the duration of assessment of post operative pain are important in the evaluation of pre-emptive analgesia. We carried out a prospective, randomized, double-blind controlled study in 80 patients of physical status ASA 1-3 undergoing upper abdominal anf thoraci c surgery. Patients received two epidural injections, one 20 minutes before induction and the other at the end of surgery. Study solution was either m orphine (50 mu g/kg), with or without 0.1% bupivacaine in 10 ml of normal s aline, or normal saline alone. The study groups (Pre M, Pre MB) were given either morphine or morphine-bupivacaine before induction and saline at the end of surgery. The control groups (Post M, Post MB) were given saline befo re induction and morphine or morphine-bupivacaine at the end of surgery. Po stoperative pain was assessed with a Visual Analogue Scale (VAS) during cou ghing and deep breathing at six-hourly intervals for five days. Epidural mo rphine was given if the VAS exceeded 4. Pre MB compared to Post MB had a significantly increased interval between t he analgesic top-ups (P<0.01) and decreased total postoperative morphine re quirements (P<0.001) and number of top-ups (P<0.001). Pre M and Post M were comparable. Pre MB compared to Pre M had significantly decreased total pos toperative morphine requirements (P<0.001) and number of top-ups (P<0.001). Epidural morphine plus bupivacaine is effective as a pre- emptive analgesi c. Morphine plus bupivacaine has better efficacy than morphine given alone before the induction of anaesthesia.