British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial Controlled Clinical Trial
Effect of racemic mixture and the (S+)-isomer of ketamine on temporal and spatial summation of pain.
We have compared the analgesic efficacy of the racemic mixture and the stereoisomer (S+) of the NMDA antagonist ketamine. In a double-blind, three-way crossover, placebo-controlled study, we assessed the following: pain evoked by small/large area pressure stimuli, pain detection threshold and pain ratings to small/large area of heat stimuli, pain detection threshold and pain rating to heat stimuli of brief/long duration, summation pain threshold and pain ratings to repeated heat/electrical stimuli, side effects and reaction time. Plasma concentrations of 350 ng ml-1 for ketamine (racemic) and 180 ng ml-1 for ketamine (S+) were tried. ⋯ Both drugs affected pain caused by repeated stimuli or stimuli of long duration equally or more than a single stimulus of short duration. They also affected pain evoked from large areas equally or more than pain evoked from small areas. The (S+)-isomer was approximately twice as potent as the racemic mixture of ketamine in inhibiting central summation.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of caudal bupivacaine and diamorphine with caudal bupivacaine alone for repair of hypospadias.
Forty-five boys undergoing repair of hypospadias were allocated randomly to one of two groups. After induction of anaesthesia, 22 patients received 0.25% caudal bupivacaine 0.5 ml kg-1 and diamorphine 30 micrograms kg-1 and the remaining 23 patients received 0.25% caudal bupivacaine 0.5 ml kg-1 alone. ⋯ There was a statistically significant reduction in early pain scores. There was also a statistically significant increase in the time to first passage of urine in those boys in the diamorphine group who were not catheterized during operation.
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Clinical Trial Controlled Clinical Trial
Midlatency auditory evoked potentials as indicators of perceptual processing during general anaesthesia.
We tested the hypothesis that midlatency auditory evoked potentials (MLAEP) can predict the occurrence of long latency AEP components (LLAEP), which are taken as evidence for perceptual processing. Forty-one patients undergoing cardiac surgery were anaesthetized with propofol and alfentanil. During several periods of surgery we recorded LLAEP. ⋯ Pa and Nb latencies were significantly shorter both before and after recording epochs in which an LLAEP waveform occurred, compared with epochs in which no LLAEP waveform occurred. Using a combination of up to six EEG, MLAEP, MAP and T measures, it was possible to predict the occurrence or absence of an LLAEP waveform with a sensitivity of 89% and specificity of 86%. We conclude that MLAEP components provide information on the possibility of perceptual processing during general anaesthesia, and thus may be relevant for monitoring depth of anaesthesia.
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We have assessed the effects of intraplantar local anaesthetics (bupivacaine and lignocaine) on carrageenan-induced oedema, mechanical allodynia and spinal c-fos protein expression. Mechanical allodynia was evaluated using the vocalization threshold to paw pressure (VTPP) every 30 min until 60, 180 or 240 min after administration of carrageenan. ⋯ Bupivacaine induced an increase in VTPP at 30 and 60 min, limitation of oedema at 60 min and a reduction in spinal c-fos expression at 60 and 180 min, but these effects were not present 240 min after carrageenan. Intraplantar infiltration with lignocaine and bupivacaine before carrageenan transiently limited signs of inflammatory pain but did not prevent them.
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We have examined the effect of profound hypothermia on gut mucosal perfusion in 20 infants, aged 1.4-45 weeks, requiring cardiopulmonary bypass (CPB). After induction of anaesthesia, a laser Doppler probe was inserted 8 cm into the patient's rectum to allow monitoring of rectal mucosal perfusion ("flux") throughout operation. Steady-state observation periods (5 min with no change in temperature or mean arterial pressure (MAP) were achieved after 10 min on CPB at 35 degrees C, after CPB-induced cooling to 15-25 degrees C, immediately before rewarming and after rewarming to 35 degrees C. ⋯ Mean flux in the first cold period (152) was significantly lower (P = 0.001) than that in the first warm CPB period (211). Post-rewarm flux (127) was significantly lower than all other CPB flux values (P = 0.004). We conclude that although hypothermia significantly reduced mucosal blood flow, rewarming produced even greater reductions in mucosal perfusion that may prove crucial in the development of mucosal hypoxia.