Anesthesia and analgesia
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Anesthesia and analgesia · Dec 1983
Comparative StudyDifferential sensitivities of mammalian nerve fibers during pregnancy.
The onset of conduction blockade in the vagus nerve of pregnant and nonpregnant rabbits was studied utilizing an in vitro sheath nerve preparation. The time required for 50% depression of the action potential (AP) of A, B, and C vagal fibers from five pregnant and six nonpregnant animals was determined after the application of bupivacaine (0.35 mM). The onset of conduction block occurred in 6.7-12.1 min in the A, B, and C fibers from pregnant animals compared to onset times of 17.9-31.6 min in nerves taken from nonpregnant rabbits. ⋯ The results suggest either an increased sensitivity of nerve fibers from pregnant animals to bupivacaine or an enhanced diffusion of the bupivacaine to the membrane receptor site. Mechanical factors are clearly not responsible for the observed results. Hormonal factors may play a role in the decreased anesthetic latency, because progesterone levels were significantly higher in the pregnant animals.
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The effect of nifedipine-induced hypotension on intracranial pressure (ICP) was investigated in cats with normal and artificially increased ICP. Eleven cats were anesthetized with intraperitoneal pentobarbital (25 mg/kg), intubated, and ventilated with nitrous oxide in oxygen. Mean arterial pressure (MAP), heart rate (HR), and mean pulmonary artery pressure (PAP) were continuously recorded. ⋯ Infusion of 96 +/- 12 micrograms (SEM) nifedipine (approximately equal to 33 micrograms/kg) reduced MAP 35-45% for 2.5 +/- 0.8 min when ICP was normal, and for 2.0 +/- 0.6 min when ICP had been increased. When initial ICP was normal, nifedipine-induced hypotension produced a small (2.2 mm Hg) but statistically significant increase in ICP and decrease in cerebral perfusion pressure (P less than 0.01). When ICP was initially elevated, nifedipine-induced hypotension produced a larger increase in ICP (5 +/- 1 mm Hg) and a proportionately larger decrease in cerebral perfusion pressure (P less than 0.01).
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The antagonism of a pancuronium-curare (P + C) neuromuscular block was assessed and compared to the antagonism of a pancuronium (P) block. One group of seven patients received P + C (0.024 mg/kg + 0.144 mg/kg); another similar group of seven patients received P (0.07 mg/kg). ⋯ The resultant antagonism of the pancuronium-curare blocks was the same as the antagonism of the pancuronium blocks (train-of-four ratio, 0.38 vs 0.32; P = 0.5). The authors conclude that neostigmine requirements for combination blocks are the same as those for single agent blocks.
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Anesthesia and analgesia · Dec 1983
Letter Historical ArticleThe first experiment in obstetrical anesthesia.