Anesthesia and analgesia
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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
A simple, fast, easy method to identify the evidence base in pain-relief research: validation of a computer search strategy used alone to identify quality randomized controlled trials.
Clinicians need a simple, fast, reliable, and inexpensive way of identifying the evidence base relevant to their clinical practice. It is often believed that the only way to identify all relevant evidence is to perform hand-searches of the literature to supplement computer searches; this is complex and labor intensive. However, most of quality randomized controlled trials cited in systematic reviews in pain medicine are listed in computer databases. We performed two studies to investigate the efficiency-in terms of sensitivity, specificity, and precision-of three computer search strategies: Optimally Sensitive Search Strategy, which is used by the Cochrane Collaboration; RCT.pt, a standard MEDLINE strategy; and DBRCT.af, which is a new single-line computer algorithm based on the assumption that double-blinded, randomized controlled trials would be indexed with "double-blind," "random," or variations of these terms in MEDLINE and EMBASE. DBRCT.af was found to be highly sensitive (97%) in identifying quality randomized controlled trials in pain medicine. The precision (ratio of randomized controlled trials to the number of nonrandomized trials identified) was 82%, and the specificity in excluding the nonrandomized controlled trials was 98%. We conclude that clinicians can now use DBRCT.af to update and conduct de novo systematic reviews in pain-relief research. ⋯ Quality evidence about what is good clinical practice in pain treatment is buried in the medical literature among large quantities of other information. This article describes how any clinician with access to the Internet can identify those quality studies reliably, quickly, and inexpensively.
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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.