Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
Clinical effects and maternal and fetal plasma concentrations of epidural ropivacaine versus bupivacaine for cesarean section.
Ropivacaine is a new amide local anesthetic structurally similar to bupivacaine and mepivacaine. Previous studies showed that ropivacaine has a similar clinical effect as bupivacaine with regard to sensory anesthesia and slightly less motor blockade than bupivacaine. Ropivacaine appears to be less cardiotoxic and arrhythmogenic than bupivacaine. The clinical and pharmacokinetic effects of 0.5% ropivacaine (5 mg/ml) versus 0.5% bupivacaine (5 mg/ml) when used epidurally for elective cesarean section were investigated. ⋯ Ropivacaine, 0.5%, epidurally provided satisfactory and similar sensory anesthesia compared to 0.5% bupivacaine for elective cesarean section. The Cmax was similar for both drugs, although the terminal half-life of ropivacaine was significantly shorter, and the blood concentrations of free ropivacaine were significantly greater than that for bupivacaine. These values were less than concentrations shown to be toxic in animals.
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Subsidiary atrial pacemakers assume control after sinoatrial (SA) node excision, and anesthetic-catecholamine interactions can produce severe bradycardia during isoflurane anesthesia. We hypothesized that epinephrine enhances atrial, atrioventricular junctional, and ventricular dysrhythmias after SA node excisions in dogs and that inhalation anesthetics would facilitate such dysrhythmias. ⋯ In dogs with excised SA nodes, anesthetic-catecholamine interaction facilitates ventricular escape, His bundle dysrhythmias, and premature ventricular beats. In addition, halothane and enflurane, more than isoflurane, facilitate ectopic ventricular tachydysrhythmias with epinephrine. Compared to intact dogs, dogs with excised SA nodes may be more susceptible to epinephrine anesthetic dysrhythmias. If findings can be extrapolated to humans, intrinsic SA node dysfunction may facilitate severe cardiac dysrhythmias with inhalation anesthetics and catecholamines.
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After upper abdominal surgery, patients have been observed to have alterations in respiratory movements of the rib cage and abdomen and respiratory shifts in pleural and abdominal pressure that suggest dysfunction of the diaphragm. The validity of making such deductions about diaphragm function from these observations is open to discussion. ⋯ Indirect measurements of respiratory muscle action based on pressure and chest wall motion are easier than are assessments based on implanted electromyogram electrodes and sonomicrometers that measure electric activity and muscle length, respectively, directly. Interpretation requires numerous assumptions and detailed analysis of phase relations among the variables. In patients after thoracic surgery, however, these measurements strongly point to a shift in the distribution of motor output toward muscles other than the diaphragm.
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Aqueous suspensions of the local anesthetic n-butyl-p-aminobenzoate (BAB), epidurally applied in terminal cancer patients, resulted in a sensory blockade, lasting up to several months. To investigate the mechanism of action on the cellular level, the effect of 100 microM BAB on Na+ action potentials and on Na+ currents in dorsal root ganglion neurons from neonatal rats was studied. ⋯ BAB dramatically increased the firing threshold, and in part of the sensory neurons, it blocked the action potential. The inactivation of the fast Na+ channels, but not of the slow Na+ channels, was increased by BAB. Thus, the block of fast Na+ channels by BAB may contribute to epidural analgesia. At exposure times of 10 min, the effect of BAB was not reversible. This probably originates from its high lipid-solubility, which may be an important factor in determining the duration of the block in vivo.