Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
The neonatal neurobehavioral effects of bupivacaine, mepivacaine, and 2-chloroprocaine used for pudendal block.
The neonatal neurobehavioral effects of bupivacaine, mepivacaine, and 2-chloroprocaine used in random sequence for pudendal block anesthesia were studied. The neurobehavioral status of 54 infants was studied 4 and 24 hours after delivery. ⋯ Mean mepivacaine levels in neonatal capillary blood at 4 hours of age were low (0.10 +/- .02 microgram/ml) compared with those in previous studies because of the short interval between maternal injection and delivery (13 +/- 3 min). Bupivacaine gave higher neonatal capillary blood levels (0.15 microgram/ml at 4 hours of age) than previously reported, but the drug still produced no detectable neonatal neurobehavioral effects.
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The authors examined the thesis that a dose of dantrolene producing 95 per cent of maximal muscle relaxation (ED95) would effectively prevent or treat malignant hyperthermia (MH). In one group of four pigs sensitive to malignant hyperthermia (MHS) a dose response to intravenous dantrolene was determined by quantitation of toe twitch tension. From these data, the ED95 relaxant dose (3.5 mg/kg) was derived. ⋯ Finally, each pig was challenged without dantrolene prophylaxis or therapeusis, and all succumbed from MH. Previous studies have shown the efficacious use of dantrolene in prevention or treatment of porcine MH, but doses used have varied, without rationale. The present study shows that in MHS pigs the ED95 muscle relaxant dose of dantrolene (3.5 mg/kg) successfully prevents and treats MH.
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Comparative Study
Whole-body distribution of radioactively labelled microspheres in the rat during anesthesia with halothane, enflurane, or ketamine.
Cardiac output and distribution of blood flow using 15-micron radioactively labelled microspheres were determined in 25 Wistar rats. In seven awake control animals, first and second injections of microspheres did not change cardiac output (137 +/- 8 ml/min) or result in alteration in apparent blood flow to the various organs studied. Halothane anesthesia (n = 6) (1.3 per cent inspired) resulted in a decrease in cardiac output, with increases in the percentages of cardiac output going to the brain, kidney, liver and large intestine. ⋯ Ketamine anesthesia (n = 6) (125 mg/kg, im) differed from the other two agents in that few changes occurred from the awake state except in brain, lung and muscle, Microspheres that were trapped after the first injection were released from muscle and skin with ketamine anesthesia, resulting in an apparent decrease in the distribution of cardiac output to muscle in the controls and an apparent increase in "flow" to the lung. The microsphere method gives reliable information about cardiac output and distribution of flow in rats anesthetized with halothane or enflurane. Further studies are necessary to determine whether microsphere studies are valid indicators of organ flow during ketamine anesthesia in the rat.