British journal of anaesthesia
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Dexmedetomidine is an alpha 2 agonist and has been reported to have proconvulsant actions. To investigate the interaction of dexmedetomidine with convulsant anaesthetics, we studied effects on seizure threshold in cats during enflurane anaesthesia. Cats were prepared with chronic implantation of electrodes for recording of the cortical electroencephalogram (EEG) and midbrain reticular formation multi-unit activity (R-MUA). ⋯ The effects of dexmedetomidine 1, 10 and 100 micrograms kg-1 i.v. and yohimbine 500 micrograms kg-1, an alpha 2 antagonist, on SII during 3.5% enflurane anaesthesia were investigated. Dexmedetomidine significantly increased SII at 10 and 100 micrograms kg-1, and this effect was reversed by yohimbine. We found that high-dose dexmedetomidine reduced seizure threshold during enflurane anaesthesia.
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We have compared the effect of increasing optode separation (range 0.7-5.5 cm) on the sensitivity of near infrared spectroscopy (NIRS) to discrete reductions in scalp and cerebral oxygenation in 10 healthy men (mean age 32, range 26-39 yr) using multichannel NIRS. During cerebral oligaemia (a mean reduction in middle cerebral artery flow velocity of 47%) induced by a mean reduction in end-tidal PCO2 of 2.4 kPa, the decrease in oxyhaemoglobin detected by NIRS became significantly greater with increasing optode separation (P < 0.0001). ⋯ These results are consistent with theoretical models of the behaviour of NIR light in the adult head and support the concept of using multi-detector NIRS to separate intra- and extracranial NIR signal changes. However, the emitter-detector separation used by currently available cerebral oximeters is not large enough to provide optimal spatial resolution.
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Randomized Controlled Trial Comparative Study Clinical Trial
Premedication with melatonin: a double-blind, placebo-controlled comparison with midazolam.
We have evaluated the perioperative effects of melatonin with those of midazolam in 75 women in a prospective, randomized, double-blind, placebo-controlled study. Patients were given sublingual midazolam 15 mg, melatonin 5 mg or placebo, approximately 100 min before a standard anaesthetic. Sedation, anxiety and orientation were quantified before, and 10, 30, 60 and 90 min after premedication, and 15, 30, 60 and 90 min after admission to the recovery room. ⋯ Amnesia was notable only in the midazolam group for one preoperative event (entry into the operating room). Patient satisfaction was noted in the midazolam and melatonin groups only. We have demonstrated that melatonin can be used effectively for premedication of adult patients.
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Randomized Controlled Trial Clinical Trial
Postoperative pain after adenoidectomy in children.
We have investigated if pain intensity or analgesic requirements in hospital predicted pain intensity, pain duration or analgesic requirements at home in 611 children, aged 1-7 yr, after day-case adenoidectomy. We also investigated if ketoprofen 0.3-3.0 mg kg-1, administered pre-emptively i.v. during operation, modified pain at home. In hospital, a prospective, randomized, double-blind, placebo-controlled study design was performed. ⋯ The response rate was 91%. The number of doses of fentanyl given in hospital correlated with pain intensity at home (P < 0.001). There were no other correlations and no pre-emptive effect of ketoprofen.
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Randomized Controlled Trial Comparative Study Clinical Trial
End-tidal sevoflurane concentration for tracheal extubation (MACEX) in adults: comparison with isoflurane.
Sevoflurane has a non-pungent odour and provides smooth induction of anaesthesia. In contrast, isoflurane is irritating to the airway when used for induction, and this may also be evident during emergence from anaesthesia. We measured the end-tidal concentration of anaesthetic that prevented response to extubation in 50% of patients (MACEX) in adults receiving either sevoflurane or isoflurane. ⋯ In 12 patients in the isoflurane group, extubation was smooth but six patients had coughing episodes during the remainder of the emergence period. In contrast, one of 15 patients in the sevoflurane group in whom tracheal extubation was smooth coughed later (P = 0.035). Airway obstruction was frequent when tracheal extubation was performed at end-tidal concentrations exceeding 1 MACEX for each anaesthetic.