British journal of anaesthesia
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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.
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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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Although subjects often report difficulty with swallowing shortly after receiving neuromuscular blocking agents, difficulty with swallowing during recovery from neuromuscular blocking agents appears to be infrequent. We have used electromyography to compare onset and recovery at the diaphragm and geniohyoid airway muscles after an intubating dose of mivacurium (0.2 mg kg-1) to determine if the geniohyoid muscles were particularly sensitive to neuromuscular blocking agents. Twelve adults undergoing elective surgery were anaesthetized with propofol and fentanyl and the trachea intubated without neuromuscular blocking agents. ⋯ Recordings were also made of the mechanical response of the adductor pollicis to supramaximal ulnar nerve stimulation. There was no difference in the rate of onset of block for geniohyoid muscles and the diaphragm, but recovery to 25% and 90% of the control response was shorter at the diaphragm (median 14.5 (95% confidence limits 12.9-15.3) min and 23.8 (21.7-26) min) than at the geniohyoid muscle (19.4 (15.6-20.1) min and 29.2 (26.3-31.4) min), respectively (P < 0.05). When the train-of-four ratio of the mechanical response of the thumb reached 70%, the diaphragm and geniohyoid muscles had recovered completely in all patients.
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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.