Anesthesia and analgesia
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Anesthesia and analgesia · Jul 1982
Comparative StudyDifferential sensitivity of fast and slow fibers in mammalian nerve. II. Margin of safety for nerve transmission.
In a previous study it was found that concentrations of local anesthetics required to block large, fast-conducting nerve fibers were lower than those required to block small, slow-conducting fibers. The present study was instituted to evaluate the margin of safety for transmission in large versus small nerve fibers, the margin of safety being defined as the ratio between the magnitude of the action potential and the magnitude of the critical membrane potential. The effect of reducing the sodium-activating current, which reduces the magnitude of the action potential by sodium deficient solutions and tetrodotoxin application to the desheathed rabbit vagus nerve trunk (in vitro), was examined. ⋯ In all instances, the margin of safety for transmission was greater in small, slow fibers than in large, fast fibers. The variations seen in nerve response to tetrodotoxin application are explained by the presence of nerve fiber diffusion barriers; the large fibers show more diffusion protection than the small fibers. Onset, duration, and intensity of differential nerve blockade by drugs reflect a balance between diffusion barriers and axon membrane sensitivity.
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Anesthesia and analgesia · Jul 1982
Comparative StudyDifferential sensitivity of fast and slow fibers in mammalian nerve. III. Effect of etidocaine and bupivacaine on fast/slow fibers.
Etidocaine and bupivacaine are long acting local anesthetics with contrasting effects on motor and sensory function. The effect of these drugs on fast-conducting (large, motor) and slow-conducting nerve fibers (small, pain) in the isolated rabbit vagus nerve was examined. Both drugs had an equivalent effect on slow fibers. ⋯ During this long latency of effect by bupivacaine on fast fibers, only the slow fibers were blocked. This period of differential effect on fast and slow fibers is believed to be the explanation for the early effect of bupivacaine on pain fibers followed by a later block of motor function. This difference is believed to be due to the lower lipid solubility solubility and greater ionization of bupivacaine, which impedes diffusion across the permeability barriers present in fast-conducting A fiber.
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Anesthesia and analgesia · Jun 1982
Comparative StudyChanging specialties: do anesthesiologists differ from other physicians?
Career choices of physicians frequently change after senior year in medical school. Although previous studies have documented the magnitude of these changes, they contain no information concerning anesthesiologists. Changes in specialties of 1151 physicians, graduates from the same medical school, between the years 1968 and 1976 were studied. ⋯ Of 31 physicians who planned careers in anesthesiology as seniors, 26 (84%) remained in anesthesiology. Nine physicians changed from other specialties to anesthesiology. The ability of anesthesiology to retain physicians who originally planned to specialize in it, or to gain physicians from other fields, was not different from that found in other specialties studied.
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Anesthesia and analgesia · Jun 1982
Continuous monitoring of mixed venous oxygen saturation in critically ill patients.
A new pulmonary artery balloon flow-directed catheter combines a fiberoptic photometric system for continuous display of mixed venous blood oxygen saturation (SvO2) with the capacity for hemodynamic measurements including thermodilution cardiac output estimation. This oximetry system was studied to determine its accuracy, reliability, and usefulness in the surgical intensive care unit (ICU). ⋯ The catheter values for SvO2 were closely related (r = 0.9516) to those obtained from a laboratory Co-oximeter. Continuous monitoring of SvO2 is accurate and valuable as a warning system for deterioration in cardiopulmonary function and as an indicator of the effects of various therapeutic maneuvers in critically ill patients.
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Anesthesia and analgesia · May 1982
Comparative StudyA model for comparison of local anesthetics in man.
Ten patients scheduled for bilateral arm surgery were given general anesthesia plus, on one side, an axillary brachial plexus block. Ten additional patients scheduled for bilateral foot surgery were similarly given general anesthesia plus an ankle block on one side. A within-patient blind comparison of postoperative analgesia between blocked and unblocked side was performed. ⋯ Postoperative analgesia recorded by a nurse observed was significantly better on the blocked side compared with the unblocked side. This difference was greater for ankle blocks. There were no differences between the analgesic measures for lidocaine and bupivacaine ankle blocks over the 6-hour study period.