British journal of anaesthesia
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Spread of intrathecal local anaesthetics is determined principally by baricity and position of the patient. Hypobaric solutions of bupivacaine are characterized by an unpredictable spread of sensory block whereas addition of dextrose 80 g ml(-1) provides a predictable spread but to high thoracic levels. In contrast, dextrose concentrations between 8 and 30 g ml(-1) have shown reliable and consistent spread for surgery. Hence, the aim of this study was to determine the density of bupivacaine, levobupivacaine, and ropivacaine with and without dextrose at both 23 and 37 degrees C before embarking on clinical studies. ⋯ The density of local anaesthetics decreases with increasing temperature and increases in a linear fashion with the addition of dextrose. Levobupivacaine 5 g ml(-1) has a significantly higher density compared with bupivacaine 5 g ml(-1) and ropivacaine 5 g ml(-1) at 23 and 37 degrees C both with and without dextrose. Levobupivacaine 7.5 g ml(-1) is an isobaric solution within all patient groups at 37 degrees C [corrected]
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Some limitations of traditional ("mamillary") compartmental pharmacokinetic models of anaesthetic related drugs arise from representing the blood as a central compartment. Recirculatory pharmacokinetic models overcome these limitations. It is proposed that the simplest recirculatory model has only two compartments, and that understanding the properties of this model is a useful introduction to recirculatory pharmacokinetic concepts. ⋯ The two-compartment recirculatory model is the simplest tool available for elaborating recirculatory pharmacokinetic concepts. The recirculatory approach may provide a conceptual framework of drug disposition that better matches the clinical experience of anaesthetists.
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Randomized Controlled Trial Comparative Study Clinical Trial
Agitation and changes of Bispectral Index and electroencephalographic-derived variables during sevoflurane induction in children: clonidine premedication reduces agitation compared with midazolam.
This double-blind randomized study was undertaken to assess agitation, Bispectral Index (BIS) and EEG changes during induction of anaesthesia with sevoflurane in children premedicated with midazolam or clonidine. ⋯ Compared with midazolam, clonidine premedication reduced agitation during sevoflurane induction. During induction with sevoflurane 8% (oxygen 50%-nitrous oxide 50%), the nadir of the BIS occurred at the end of the second minute of inhalation. Agitation was associated with a more pronounced slowing of the EEG rhythms at BIS(nadir) compared with inductions in which no agitation was observed. The BIS may not follow the depth of anaesthesia during sevoflurane induction in children.
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Randomized Controlled Trial Clinical Trial
Randomized, controlled trial of the double setup tracheal tube during fibreoptic orotracheal intubation under general anaesthesia.
Impingement of the tracheal tube (ETT) on upper airway structures during railroading over the fibreoptic bronchoscope (FOB) occurs commonly. Potential complications of impingement include prolonged intubation time, leading to arterial desaturation, failed intubation and laryngeal trauma. The objective of this randomized, controlled trial was to assess the effect of the double setup ETT (a paediatric ETT is placed inside an adult ETT) on the incidence of impingement during orotracheal fibreoptic intubation. ⋯ The double setup ETT is effective in reducing ETT impingement and in reducing intubation time. We did not find an association between ETT impingement and arterial desaturation.
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Clinical Trial Controlled Clinical Trial
Pharmacokinetics of remifentanil and its major metabolite, remifentanil acid, in ICU patients with renal impairment.
The pharmacokinetics of remifentanil, an opioid analgesic metabolized by non-specific esterases, and its principal metabolite, remifentanil acid (RA), which is excreted via the kidneys, were assessed as part of an open-label safety study in intensive care unit (ICU) patients with varying degrees of renal impairment. ⋯ Although RA accumulates in patients with moderate/severe renal impairment, pharmacokinetic modelling predicts that RA concentrations during a 9 microg kg(-1) h(-1) remifentanil infusion for up to 15 days would not exceed those reported in the present study, for which no associated prolongation of mu-opioid effects was observed.