Anesthesia and analgesia
-
Anesthesia and analgesia · Jun 2004
Randomized Controlled Trial Comparative Study Clinical TrialThe synergistic effect of combined treatment with systemic ketamine and morphine on experimentally induced windup-like pain in humans.
In this study, we evaluated whether combined treatment with ketamine (KET), an N-methyl-D-aspartate receptor antagonist, and morphine (MO) results in positive analgesic effects. Eleven volunteers were exposed to a skin burn injury on the leg. The effects of IV KET (9 microg. kg(-1). min(-1); 45 min) and MO (10 microg. kg(-1). min(-1); 10 min) alone and in combination, as well as placebo (saline; 10 min), were studied in a randomized, crossover, double-blinded design. The area of secondary hyperalgesia (SH) for mechanical stimulation was diminished by KET as compared with placebo. Mechanical pain thresholds were increased severalfold with KET and with KET plus MO, both in the primary hyperalgesic (PH; burn injury) and SH area. MO infusion showed no effect on the SH area or pain threshold. Windup-like pain was evaluated by continuous assessment on a visual analog scale during 30 s of repetitive stimulation (40-g load at 3 Hz) and analyzed as a sum of pain scores. The combined treatment (KET plus MO) almost abolished windup-like pain both in the PH and the SH areas, an effect that was not present with monotherapy with KET or MO. This study provides experimental support for a positive analgesic interaction between an N-methyl-D-aspartate receptor antagonist and an opioid on central summation of pain. ⋯ This is the first experimental study in humans to find synergistic analgesic effects with coadministration of the N-methyl-D-aspartate receptor antagonist ketamine and morphine on pain involving central sensitization phenomena.
-
Anesthesia and analgesia · Jun 2004
Randomized Controlled Trial Comparative Study Clinical TrialModerate-to-severe pain after knee arthroscopy is relieved by intraarticular saline: a randomized controlled trial.
We have previously studied intraarticular (IA) analgesics compared with saline 10 mL in 2 randomized clinical trials. The patients who were given IA saline experienced rapid pain relief. Hypothetically, saline may produce a local analgesic effect by cooling or by diluting IA algogenic substances. This randomized double-blind study compared the analgesic effect of IA saline 10 mL with saline 1 mL, which should be a pure placebo. A soft catheter was left IA in 79 patients. We included 60 patients who developed moderate-to-severe pain within 1 h after knee arthroscopy under general anesthesia. A randomized, double-blind controlled comparison of IA saline 10 mL with saline 1 mL followed. Outcome measures were pain intensity, pain relief, and analgesic consumption. Within 1 h pain intensity decreased in both groups from approximately 50 to approximately 27 on a 0-100 mm visual analog scale. Pain intensity remained low and other pain outcome measures were similar during the 36-h observation period. The patients experienced equally good pain relief after IA injection of saline 10 mL and 1 mL. Our finding of a major placebo effect may have implications for the interpretation of previously published placebo-controlled IA analgesia studies. ⋯ In a randomized controlled trial we showed that pain after knee arthroscopy is modest and short-lived and can successfully be treated with intraarticular saline as placebo.
-
Anesthesia and analgesia · Jun 2004
Comparative StudyMorphine-induced analgesia, hypotension, and bradycardia are enhanced in hypertensive rats.
Several studies have emphasized an opioidergic link between the central regulation of cardiovascular function and acute noninflammatory pain. By contrast, relatively few studies have investigated the relationships between opioids, hypertension, and inflammatory pain. We used the formalin model of acute inflammatory pain to compare morphine antinociception among spontaneously hypertensive (SHR) rats, their genetic normotensive controls, Wistar-Kyoto (WKY) rats, and Sprague-Dawley (SD) rats. Measures of nociception included both behavioral and cardiovascular end-points (increased mean arterial blood pressure and heart rate). Morphine (3.0 mg/kg subcutaneously) produced greater hypotension and bradycardia in SHR than in WKY or SD rats. We next administered formalin (5%; 50 microL) and observed greater nociception during both Phase 1 and Phase 2 in SHR controls than in WKY controls. The morphine-treated groups did not differ, suggesting that morphine attenuates hypersensitivity to formalin pain in the SHR. Morphine inhibited edema but not paw hyperthermia to a greater degree in SHR, whereas Phase 1 remifentanil produced a relatively shorter delay in the onset of Phase 2 in SHR. We suggest that the presentation of essential hypertension be considered when opioid regimens are planned both during surgery (to minimize cardiovascular complications) and during the postoperative period (to optimize analgesic effects). ⋯ Presentation of essential hypertension should be considered when opioid regimens are planned both during surgery (to minimize cardiovascular complications) and during the postoperative period (to optimize analgesic effects).