British journal of anaesthesia
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Comparative Study
Comparison of relaxant effects of propofol on methacholine-induced bronchoconstriction in dogs with and without vagotomy.
Propofol has been suggested to have in vivo airway relaxant effects, although the mechanism is still unclear. In this study, we determined whether propofol could antagonize methacholine-induced bronchoconstriction and determined whether vagotomy modifies this relaxant effect. Fourteen mongrel dogs anaesthetized with pentobarbital and pancuronium were assigned to a control group (n=7) and a vagotomy group (n=7). ⋯ The two groups did not differ significantly in the maximal inhibitory effect of propofol [control group, 61.1% (46.3-75.9%), vagotomy group, 64.2% (40.1-88.3%)] or pIC50 [control group 5.03 (4.55-5.51), vagotomy group 4.86 (4.49-5.24)]. Therefore, the relaxant effects of propofol on methacholine-induced bronchoconstriction may not be mediated centrally. Propofol may relax airway smooth muscles directly or through the peripheral vagal pathway.
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Differences in the pharmacokinetics of propofol between male and female patients during and after continuous infusion have not been described in detail in patients aged 65 yr and older. To increase our insight into the pharmacokinetics of propofol in this patient population and to obtain pharmacokinetic parameters applicable in target controlled infusion (TCI), the pharmacokinetics of propofol during and after continuous infusion were studied in 31 ASA class 1 and 2 patients, aged 65-91 yr, scheduled for general surgery. Patients received propofol 1.5 mg kg(-1) i.v. in 1 min followed by 7 mg kg(-1) h(-1) until skin closure in the presence of a variable rate infusion of alfentanil during oxygen-air ventilation. ⋯ Gender significantly affected the pharmacokinetics of propofol. V3, Cl1 and Cl2 were significantly different between male and female patients, weight only affected Cl1. The pharmacokinetic parameters were: V1=4.88 litre, V2=24.50 litre, V3 (litre)=115+147 x gender (gender: male=1, female=2), Cl1 (litre min(-1))=-0.29+0.022 x weight+0.22 x gender, Cl2 (litre min(-1))=2.84-0.65 x gender (male=1, female=2), and Cl3=0.788 litre min(-1).
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Ischaemic preconditioning can protect the myocardium against ischaemic injury by opening of the adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channel. Isoflurane is also thought to open this channel. The present investigation tested the hypothesis that pre-ischaemic treatment with isoflurane mimics ischaemic preconditioning (producing chemical preconditioning) and thereby protects the myocardium against ischaemic injury in an isolated rat heart model. ⋯ Recovery of LV developed pressure was improved after ischaemic preconditioning [after 60 min reperfusion, mean 63 (SEM 6)% of baseline] compared with the control group [18 (4)% P<0.01] but not by isoflurane, independently of concentration or duration of administration [ISO-1, 17 (2)%, P=0.99 vs control; ISO-2, 12 (3)%, P=0.64; ISO-3, 4 (1)%, P=0.06]. Total creatine kinase release over 1 h of reperfusion was not significantly different between control [251 (36) U g(-1) dry weight] and all isoflurane groups [ISO-1, 346 (24) U g(-1), P=0.30; ISO-2, 313 (33) U g(-1), P=0.73; ISO-3, 407 (40) U g(-1), P=0.03]. These results indicate that pre-ischaemic administration of isoflurane does not cause anaesthetic-induced preconditioning in the isolated rat heart.
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Randomized Controlled Trial Clinical Trial
Absence of memory for intra-operative information during surgery with total intravenous anaesthesia.
While using the isolated forearm technique, we wished to determine whether patients who did not respond to commands during general anaesthesia with a total intravenous technique (propofol and alfentanil with atracurium) had any evidence of post-operative explicit or implicit memory. Forty women undergoing major gynaecological surgery were randomized, in a double-blind design, to hear two different tapes during surgery. ⋯ We conclude that during total intravenous anaesthesia with propofol and alfentanil, there is no evidence that learning takes place when anaesthesia is adequate. Furthermore, with this anaesthetic technique, it would seem that--provided any period of patient responsiveness is short and that unconsciousness is induced rapidly again--there is no evidence of implicit or explicit memory.
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Randomized Controlled Trial Comparative Study Clinical Trial
Sevoflurane EC50 and EC95 values for laryngeal mask insertion and tracheal intubation in children.
The laryngeal mask airway (LMA) is a simple, easy to use and safe method for airway control in children. Its insertion needs less anaesthetic, and haemodynamic responses and postoperative sequelae are less than with laryngoscopy and tracheal intubation. This study was designed to determine the end-tidal concentrations of sevoflurane where 50% (EC50) and 95% (EC95) of the attempts to secure the airway would be successful. ⋯ Sevoflurane provided good conditions for both LMA insertion, and laryngoscopy and tracheal intubation without serious adverse effects. The EC50 and the EC95 of sevoflurane were 1.57 (SD 0.33)% and 2.22% for LMA insertion and 2.20 (SD 0.31)% and 2.62% for laryngoscopy and tracheal intubation. Thus, less sevoflurane is required for LMA insertion in children than for laryngoscopy and tracheal intubation.