Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2004
Randomized Controlled Trial Comparative Study Clinical TrialThe impact of heparin-coated cardiopulmonary bypass circuits on pulmonary function and the release of inflammatory mediators.
Reduction of the inflammatory reaction with the use of heparin coating has been found during and after cardiopulmonary bypass (CPB). The question remains whether this reduced reaction also decreases the magnitude of CPB-induced pulmonary dysfunction. We therefore evaluated the effects of a heparin-coated circuit versus a similar uncoated circuit on pulmonary indices as well as on inflammatory markers of complement activation (C3b/c), elastase-alpha(1)-antitrypsin complex, and secretory phospholipase A(2) (sPLA(2)) during and after CPB. Fifty-one patients were randomly assigned into two groups undergoing coronary artery bypass grafting with either a heparin-coated (Group 1) or an uncoated (Group 2) circuit. During CPB, a continuous positive airway pressure of 5 cm H(2)O and a fraction of inspired oxygen (FIO(2)) of 0.21 were maintained. Differences in favor of the coated circuit were found in pulmonary shunt fraction (P < 0.05), pulmonary vascular resistance index (P < 0.05), and PaO(2)/FIO(2) ratio (P < 0.05) after CPB and in the intensive care unit. During and after CPB, the coated group demonstrated lower levels of sPLA(2). After CPB, C3b/c and the elastase-alpha(1)-antitrypsin complex were significantly less in the coated group (P < 0.001). The coated circuit was associated with a reduced inflammatory response, decreased pulmonary vascular resistance index and pulmonary shunt fraction, and increased PaO(2)/FIO(2) ratio, suggesting that the coated circuit may have beneficial effects on pulmonary function. The correlation with sPLA(2), leukocyte activation, and postoperative leukocyte count suggests reduced activation of pulmonary capillary endothelial cells. ⋯ Heparin coating of the extracorporeal circuit reduces the inflammatory response during cardiopulmonary bypass. Analysis of indices of pulmonary function indicates that use of heparin coating may result in less impaired gas exchange.
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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.
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Anesthesia and analgesia · Jun 2004
Randomized Controlled Trial Comparative Study Clinical TrialThe relative motor blocking potencies of intrathecal ropivacaine: effects of concentration.
This study established the median effective dose (ED(50)) for motor block of intrathecal 1% and 0.1% ropivacaine and determined the effects of the concentration of the solution injected on the motor block obtained. We enrolled into this prospective, randomized, double-blind, sequential allocation study 54 parturients undergoing elective Cesarean delivery under combined spinal-epidural technique. Parturients were randomized to receive intrathecal ropivacaine either 1% or 0.1%. The initial dose was chosen to be 4 mg, with subsequent doses being determined by the response of the previous patient (testing interval, 1 mg). The occurrence of any motor block in either lower limb within 5 min from the intrathecal injection of the study solution was considered effective. The motor block at 5 min was 6.1 mg for 1% ropivacaine (95% confidence interval [CI], 5.1-7.1) and was 9.1 mg (95% CI, 7.8-10.3) for 0.1% ropivacaine (P = 0.0013; 95% CI difference, 1.3-4.7). The relative efficacy ratio of the 2 concentrations was 1.5 (95% CI difference, 1.2-1.9) in favor of the larger concentration. The ED(50) of spinal ropivacaine to produce motor block in pregnant patients was significantly influenced by the concentration of the local anesthetic, with dose requirements being increased by 50% for the smaller concentration. ⋯ The minimum local anesthetic dose for motor block with 0.1% ropivacaine is 50% larger than the 1% concentration with a relative efficacy ratio of 1.5. Our findings suggest that more diluted local anesthetic solutions determine less motor block, and this may be considered in ambulant laboring parturients.
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Anesthesia and analgesia · Jun 2004
Randomized Controlled Trial Comparative Study Clinical TrialMethadone for the induction of anesthesia: plasma histamine concentration, arterial blood pressure, and heart rate.
Despite the widespread use of methadone for the treatment of acute and chronic pain, the hemodynamic effects of methadone administered by IV bolus have not been studied. We compared the hemodynamic effects of an IV bolus of methadone 20 mg with those of fentanyl 10 microg/kg for the induction of anesthesia in combination with etomidate 0.3 mg/kg. Forty-three patients undergoing major surgery were randomized to one of the two treatments in a double-blinded fashion. Plasma concentrations of histamine were measured before and 2 min after opioid administration. Heart rate and arterial blood pressure were measured via an arterial line just before opioid administration, etomidate administration, and tracheal intubation; during intubation; and 1 min after intubation. There were no significant differences in mean heart rate between the methadone and fentanyl groups at any time point. Systolic and diastolic blood pressures were significantly lower (P < 0.05) in the fentanyl group just before intubation, during intubation, and 1 min after intubation. Mean plasma concentrations of histamine before and after the administration of methadone or fentanyl were 1.54 ng/mL (SD, 0.65 ng/mL) and 1.57 ng/mL (SD, 1.37 ng/mL) or 1.00 ng/mL (SD, 0.58 ng/mL) and 1.04 ng/mL (SD, 0.47 ng/mL), respectively. Despite the lack of a significant change in mean plasma concentrations of histamine, substantial increases in plasma histamine occurred in 2 of 23 patients who received methadone. There were no obvious hemodynamic effects associated with histamine concentrations up to 6.2 ng/mL. Methadone appears to have the potential for producing histamine release. Although methadone administration did not produce hemodynamic instability in this study, the possible hemodynamic side effects of histamine release should be considered when IV boluses of methadone are given. ⋯ The same dose of IV methadone (20 mg) that is effective for postoperative pain is also suitable for the induction of anesthesia in combination with etomidate. The plasma histamine concentration was notably increased in two patients, without obvious hemodynamic sequelae. Therefore, methadone appears to have the potential for producing histamine release.
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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.