Anesthesiology
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Effects of morphine sulfate upon activity of the neurons of dorsal-horn lamina V as evoked by graded noxious thermal stimuli applied on the receptive field were studied in spinal cord-transected, decerebrate cats utilizing an extracellular microelectrode recording technique. All single units studied (n = 30) responded to noxious thermal as well as to noxious mechanical stimulation. Their spontaneous discharge frequency was 9.7 +/- 1.5 (mean +/- 1 SE) impulses/sec (IPS), the threshold skin temperature was 44.8 +/- 0.2 C, and a linear correlation existed between skin temperature and discharge frequency at 6.7 +/- 0.6 IPS/degree C. ⋯ Naloxone, 0.02--0.04 mg/kg, iv, reversed all of these changes produced by morphine. The results of the present study are, to the authors' knowledge, the first demonstration of the suppressive effect of morphine on the spinal nociceptive neurons in Rexed lamina V as they respond to graded noxious thermal stimuli. These results may explain the analgesic action of morphine at the spinal level.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of a chloroprocaine--bupivacaine mixture with chloroprocaine and bupivacaine used individually for obstetric epidural analgesia.
Continuous lumbar epidural anesthesia was instituted in 49 healthy parturients who were randomly assigned to three treatment groups: 14 patients received chloroprocaine, 3 per cent; 19 received bupivacaine, 0.5 per cent, and 16 received a mixture containing chloroprocaine, 1.5 per cent, and bupivacaine, 0.375 per cent. Observations relating to the characteristics of the anesthetic block and to maternal and fetal well-being were made by a trained nurse observer. ⋯ No clinical superiority could be demonstrate for the mixture as compared with bupivacaine or chloroprocaine used individually. There was no sign of material or fetal toxicity with any of the three treatment regimens.