Preemptive analgesia by intravenous low-dose ketamine and epidural morphine in gastrectomy - A randomized double-blind study

Background: Morphine and ketamine may prevent central sensitization during surgery and result in preemptive analgesia. The reliability of preemptive a nalgesia, however, is controversial. Methods: Gastrectomy patients were given preemptive analgesia consisting of epidural morphine, intravenous low-dose ketamine, and combinations of thes e in a randomized, double-blind manner. Postsurgical pain intensity was rat ed by a visual analog scale, a categoric pain evaluation, and cumulative mo rphine consumption. Results: Preemptive analgesia by epidural morphine and by Intravenous low-d ose ketamine were significantly effective but not definitive. With epidural morphine, a significant reduction in visual analog scale scores at rest wa s observed at 24 and 48 h, and morphine consumption was significantly lower at 6 and It h, compared with control values. With intravenous ketamine, vi sual analog scale scores at rest and morphine consumption were significantl y lower at 6, 12, 24, and 48 h than those in control subjects. The combinat ion of epidural morphine and intravenous ketamine provided definitive preem ptive analgesia: Visual analog scale scores at rest and morphine consumptio n were significantly the lowest at 6, 12, 24, and 48 h, and the visual anal og scale score during movement and the categoric pain score also were signi ficantly the lowest among the groups. Conclusion: The results suggest that for definitive preemptive analgesia, b lockade of opioid and N-methyl-D-aspartate receptors is necessary for upper abdominal surgery such as gastrectomy; singly, either treatment provided s ignificant, but not definitive, postsurgical pain relief. Epidural morphine may affect the spinal cord segmentally, whereas intravenous ketamine may b lock brain stem sensitization ain the vagus nerve during upper abdominal su rgery.