S Alam1, Y Saito, Y Kosaka. 1. Department of Anesthesiology, Shimane Medical University, Izumo, Japan.
Abstract
PURPOSE: To evaluate the antinociceptive effect of epidural and intravenous ketamine on somatic and visceral stimuli and to address the emergency reaction. METHODS: Rats were randomly allocated into nine groups (n = 6); five groups with chronically implanted epidural catheters received saline or 0.5, 1, 2 and 4 mg. kg-1 ketamine epidurally, four groups received saline, or 1, 5 and 10 mg. kg-1 ketamine i.v. To assess somatic and visceral antinociceptive effects, tail flick (TF) test and colorectal distension (CD) test were carried out, respectively. Emergence reactions were graded. Maximal possible effects (% MPE) were calculated. RESULTS: Epidural ketamine increased % MPE in both tests in a dose-dependent fashion for 30 min (vs saline group, P < 0.05). Epidural ketamine 0.5 mg. kg-1 produced an increase in % MPE in the CD test (P < 0.05) but failed in the TF test. Intravenous ketamine, 10 mg. kg-1, produced 100 +/- 0 (mean +/- SE) % MPE in the CD test but 36 +/- 15% MPE in the TF test. Dose response curves indicated greater visceral antinociception than somatic. All rats showed emergence reactions following intravenous ketamine 10 and 5 mg. kg-1. CONCLUSION: Both epidural and intravenous ketamine produce greater antinociceptive effects to visceral than to somatic stimulation, and that epidural ketamine has a low incidence of emergence reactions.
PURPOSE: To evaluate the antinociceptive effect of epidural and intravenous ketamine on somatic and visceral stimuli and to address the emergency reaction. METHODS:Rats were randomly allocated into nine groups (n = 6); five groups with chronically implanted epidural catheters received saline or 0.5, 1, 2 and 4 mg. kg-1 ketamine epidurally, four groups received saline, or 1, 5 and 10 mg. kg-1 ketamine i.v. To assess somatic and visceral antinociceptive effects, tail flick (TF) test and colorectal distension (CD) test were carried out, respectively. Emergence reactions were graded. Maximal possible effects (% MPE) were calculated. RESULTS: Epidural ketamine increased % MPE in both tests in a dose-dependent fashion for 30 min (vs saline group, P < 0.05). Epidural ketamine 0.5 mg. kg-1 produced an increase in % MPE in the CD test (P < 0.05) but failed in the TF test. Intravenous ketamine, 10 mg. kg-1, produced 100 +/- 0 (mean +/- SE) % MPE in the CD test but 36 +/- 15% MPE in the TF test. Dose response curves indicated greater visceral antinociception than somatic. All rats showed emergence reactions following intravenous ketamine 10 and 5 mg. kg-1. CONCLUSION: Both epidural and intravenous ketamine produce greater antinociceptive effects to visceral than to somatic stimulation, and that epidural ketamine has a low incidence of emergence reactions.