Epidural Morphine Does not Reduce Mean Inspired Concentration of Isoflurane in Humans during General Anesthesia

Abstract

The effect of epidural morphine on the mean inspired concentration of isoflurane was inves- tigated in 34 patients undergoing hepatoma surgery, The patients were randomly assigned to the control (CTRL), epidural morphine (MORP) or epidural bupivacaine (BUPI) groups. Before induction of anesthesia, epidural catheter was inserted beween T6-10 intervertebral space in the right lateral decubitus position. MORP group (n=13) received morphine sulfate 4 mg in 4 ml normal saline and BUPI group (n=10) received 0.5% bupivacame 10 md through epidural eatheter. CTRL group (n=11) wss treated in an identical fashion except that, after placement of epidural catheter, nothing was injected. After endotracheal intubation, general anesthesia was maintained during surgery with oxygen-nitrous oxide (1:1 ratio) and isoflurane. Inspired concentration of isoflurane was adjusted to maintain blood pressure in the range of blood pressure at the ward during surgery. Mean inspired concentration of isoflurane was monitored from incision to last skin suture. Mean inspired concentration of isoflurane (+/-SD) of CTRL, MORP and BUPI group was 1.41+/-0.36, 1.52+/-0.39 and 0.37+/-0.16 vol%, respectively. There was no difference in mean inspired concentration of isoflurane between CTRL and MORP group. Under the condition of this study, epidural morphine did not reduce inspired concentration of isoflurane during surgery even though epidural morphine is effective for post operative pain control. [By kind permission, KoreaMed, Korean Association of Medical Journal Editors.]