Anesthesiology
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Controversy still surrounds the differential susceptibility of nerve fibers to local anesthetics and its relation to selective functional deficits. In the current study we report features of conduction blockade in different classes of rat sciatic nerve fibers after injection of lidocaine by a percutaneous procedure that closely resembles clinical applications. ⋯ Susceptibility to lidocaine does not strictly follow the "size principle" that smaller (slower) axons are always blocked first. This order of fiber blockade is qualitatively consistent with previous reports of the order of functional deficits in the rat after percutaneous lidocaine, that is, motor = proprioception > nociception, if we assume that motor deficits first arise from conduction failure in Agamma fibers and that nociception relies on C fiber conduction.
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Randomized Controlled Trial Clinical Trial
Spinal ropivacaine for cesarean section: a dose-finding study.
The dose-response relation for spinal ropivacaine is undetermined, and there are few data available for obstetric patients. ⋯ The ED50 and estimated ED95 for spinal ropivacaine were 16.7 and 26.8 mg, respectively. Ropivacaine is a suitable agent for spinal anesthesia for cesarean delivery.
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Randomized Controlled Trial Clinical Trial
Effect of clonidine on lidocaine clearance in vivo: a microdialysis study in humans.
The addition of clonidine to local anesthetics has been shown to prolong both peripheral and central neuraxial local anesthetic blocks. Whether clonidine prolongs local anesthetic block by a pharmacokinetic effect or a pharmacodynamic effect is unclear. By directly measuring lidocaine tissue concentrations at the site of injection in the presence and absence of clonidine, this study was designed to address this question. ⋯ When added to lidocaine, clonidine prolonged peripheral nerve block. The pharmacokinetic data suggest that the mechanism of prolongation is at least in part pharmacokinetic.
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Clinical Trial
Differential sensitivity of abdominal muscles and the diaphragm to mivacurium: an electromyographic study.
Respiratory muscles are considered to be more resistant to muscle relaxants as compared with peripheral muscles. However, the relative sensitivity of respiratory muscles participating to the pump function has not been compared. We used electromyography to compare pharmacodynamic parameters of the diaphragm and abdominal muscles after mivacurium. ⋯ Diaphragm and abdominal muscles have differential sensitivity to mivacurium. The diaphragm is more resistant to mivacurium than abdominal muscles are.
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Comparative Study
Isoflurane and sevoflurane anesthesia in pigs with a preexistent gas exchange defect.
Decreased arterial partial pressure of oxygen (PaO2) during volatile anesthesia is well-known. Halothane has been examined with the multiple inert gas elimination technique and has been shown to alter the distribution of pulmonary blood flow and thus PaO2. The effects of isoflurane and sevoflurane on pulmonary gas exchange remain unknown. The authors hypothesized that sevoflurane with a relatively high minimum alveolar concentration (MAC) would result in significantly more gas exchange disturbances in comparison with isoflurane or control. ⋯ In pigs with an already existent gas exchange defect, sevoflurane anesthesia but not isoflurane anesthesia causes significantly more gas exchange disturbances than propofol anesthesia does.