Anesthesia and analgesia
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Anesthesia and analgesia · Aug 1982
Maternal, fetal, and neonatal responses after epidural anesthesia with bupivacaine, 2-chloroprocaine, or lidocaine.
The effects of epidural analgesia on fetal heart rate, fetal heart rate variability, uterine activity, maternal blood pressure, newborn Apgar scores, neonatal acid base status, and the early neonatal neurobehavioral status were studied in 150 parturients during labor and delivery. Group I (n = 50) received 0.5% bupivacaine, group II (n = 50) received 2% 2-chloroprocaine, and in group III (n = 50) received 1.5% lidocaine. None of the three local anesthetics used had any significant effect on either base line fetal heart rate, beat-to-beat variability, or uterine activity. ⋯ The difference in incidence of late deceleration patterns between groups I and II was statistically significant (p less than 0.025). Early neonatal neurobehavioral status did not differ among the three groups of neonates nor did any of the neonates in the three groups score lower than a control group of 20 neonates whose mothers did not receive any analgesia or medications for labor or delivery. It is concluded that epidural anesthesia as administered in this study has no significant effect on the base line fetal heart rate, uterine activity, or neurobehavioral status of the neonate, and that bupivacaine is associated with a higher incidence of what appears to be transient abnormalities of fetal heart rate.
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Anesthesia and analgesia · Aug 1982
Acid-base status of diabetic mothers and their infants following spinal anesthesia for cesarean section.
Acid-base status and Apgar scores were evaluated in 10 rigidly controlled insulin-dependent diabetic mothers and 10 healthy nondiabetic control women having spinal anesthesia for cesarean section. Dextrose-free intravenous solutions were used for volume expansion before induction of anesthesia, and hypotension was prevented in all cases by prompt treatment with ephedrine. ⋯ Apgar scores were also similar in the two groups. If maternal diabetes is well controlled, if dextrose-containing solutions are not used for maternal intravascular volume expansion before delivery, and if maternal hypotension is avoided, spinal anesthesia can be used safely for diabetic mothers having cesarean section.
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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.