British journal of anaesthesia
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The use of the equimolecular mixture of oxygen and nitrous oxide is widely recommended for relief of pain in children undergoing minor procedures. Although the benefits and adverse effects of the clinical use of nitrous oxide seem well known, its effects on the autonomic nervous system have never been studied in children. The aim of this study was to evaluate changes in autonomic cardiovascular activity induced by brief exposure to 50% nitrous oxide in children. This study was based on non-invasive continuous recordings of RR-interval and non-invasive arterial pressure. Vascular and cardiac sympathetic activity and cardiac parasympathetic activity were investigated using spectral analysis of systolic arterial pressure variability (SAPV) and RR-interval variability (RRIV). In addition, the sensitivity of the spontaneous baroreflex (SBR) was assessed using the sequences and the cross-spectral analysis methods. ⋯ Unlike the results demonstrated in adults, our findings show very few cardiovascular effects of nitrous oxide in children. Furthermore, whereas in adults nitrous oxide is associated with an excitatory cardiovascular profile, in children this agent seems to be associated with a depressant cardiovascular profile. The rapid return to baseline after discontinuation of administration and the absence of baroreflex changes are positive attributes for the use of nitrous oxide in children.
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Ketamine has been found to exert antinociceptive effects in animals and to be analgesic at subanaesthetic doses in humans. This study was designed to investigate the involvement of spinal cord mechanisms in the potentiation of opioid analgesia by parenteral non-spinal administration of ketamine. ⋯ We conclude that ketamine can potentiate the effects of fentanyl by an interaction at the level of the spinal cord even when ketamine is given via a non-spinal route of administration.
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The pharmacokinetics of propofol in man is characterized by a rapid metabolic clearance linked to glucuronidation of the parent drug to form the propofol-glucuronide (PG) and sulfo- and glucuro-conjugation of hydroxylated metabolite via cytochrome P450 to produce three other conjugates. The purpose of this study was to assess the urine metabolite profile of propofol following i.v. propofol anaesthesia in a Caucasian population. ⋯ We conclude that the extent of hydroxylation in propofol metabolism was higher than in previous findings after administration of anaesthetic doses of propofol. Moreover, the ratio between hydroxylation and glucuronidation of propofol is subject to an inter-patient variability but this does not correlate with the dose of propofol. However, the variation of the metabolite profile observed in the present report does not seem to indicate an extended role of metabolism in pharmacokinetic variability.