British journal of anaesthesia
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Clinical Trial Controlled Clinical Trial
Concentration-related effects of propofol on the auditory evoked response.
We have studied the effects of propofol, as the sole agent, at blood concentrations of 1-10 micrograms ml-1, on the first 100 ms of the auditory evoked response (AER) in 41 women before gynaecological surgery. AER were recorded with the patients awake and then after 30 min of one of seven stepped infusion regimens. Each patient was studied at only one blood concentration. ⋯ A cut-off value of 53 ms had a sensitivity of 100%, a specificity of 96% and an overall correctness of 98% as a discriminator of eyelash response vs no response. Several alternative AER-derived indices provided more than 90% correctness in discrimination, as did a dose rate of propofol of 6.3-7.8 mg kg-1 h-1 or a blood concentration of 2.9 micrograms ml-1. We conclude that the concentration and dose of propofol were good discriminators of response to venepuncture, while the latency of the Na wave was the most successful of the AER features.
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Comparative Study
Measurement of cardiac output by transoesophageal Doppler echocardiography in anaesthetized horses: comparison with thermodilution.
In order to determine if transoesophageal Doppler echocardiography could be used to estimate cardiac output in anaesthetized horses, we have compared the technique with estimations of cardiac output by thermodilution in eight healthy adult thoroughbreds. Measurements of aortic blood flow velocity were made by high pulse repetition frequency (HPRF) and continuous wave (CW) Doppler echocardiography from a 3.5-MHz transoesophageal probe. Cardiac output was increased during the study by administration of dobutamine, providing a range of cardiac output measurements by thermodilution from 15.0 to 64.4 liter min-1. ⋯ There were significant differences in bias between both Doppler techniques and thermodilution for individual horses. As a result, for any individual horse, limits of agreement between the techniques were closer (HPRF = +/- 6.4 litre min-1, CW = +/- 7.6 litre min-1). We conclude that transoesophageal echocardiography provided an alternative, effective and non-invasive method for measurement of cardiac output in anaesthetized horses.
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Clinical Trial
Propofol or halothane anaesthesia for children with asthma: effects on respiratory mechanics.
Propofol may cause histamine release and alter airway tone and reactivity. Although its use has been reported to be safe in asthmatics, there is a lack of information on its effect on lung function in children with asthma. We measured respiratory mechanics after i.v. or inhalation anaesthesia in 60 children, aged 2-12 yr, with or without asthma. ⋯ Halothane produced a minimal decrease in Rrs and a minimal increase in tidal volume in both groups without changes in Crs,dyn. In conclusion, respiratory mechanics were comparable after propofol anaesthesia in both children with and without asthma. Changes in Rrs after halothane administration were not clinically relevant.
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Randomized Controlled Trial Comparative Study Clinical Trial
Dose-response relationships for neostigmine antagonism of rocuronium-induced neuromuscular block in children and adults.
Dose-response relationships for the antagonism of intermediate-acting neuromuscular blocking agents have not been evaluated previously in children. We have examined the dose-response relationships for neostigmine antagonism of 90% rocuronium-induced neuromuscular block in children and adults, during nitrous oxide-1 MAC of isoflurane anaesthesia. We studied 40 children, aged 2-10 yr, and 50 adults, aged 18-60 yr; all received a single bolus dose of rocuronium 0.6 mg kg-1 and accelerometry was used to monitor neuromuscular transmission. ⋯ The effective doses of neostigmine required to achieve a TOF ratio of 80% (ED80) after 10 min in children and adults were, respectively, 7.10 (5.2-9.8) micrograms kg-1 and 56.56 (45.5-71.9) micrograms kg-1 (P < 0.001). There was no advantage in administering doses of neostigmine greater than 20 micrograms kg-1 to antagonize 90% rocuronium-induced neuromuscular block in children. In contrast, it appeared prudent to use neostigmine 50 micrograms kg-1 or more for adequate antagonism of a similar degree of block in adults.