British journal of anaesthesia
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Clinical Trial Controlled Clinical Trial
Laryngeal mask airway performance: effect of cuff deflation during anaesthesia.
We studied the effect of deflating the laryngeal mask airway (LMA) cuff in situ on recorded respiratory tidal ventilation in 30 spontaneously breathing anaesthetized patients. Another 26 patients were studied in whom the LMA cuff was undisturbed. ⋯ Complete cuff deflation, however, resulted in a 17% decrease in mean tidal ventilation (P < 0.05), with two patients (6%) demonstrating a substantial leak around the cuff and airway obstruction. The practice of complete cuff deflation during the recovery period from anaesthesia cannot be recommended.
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It has been suggested that haemodilution with saline may increase whole blood coagulation. This study was conducted in two parts. First, we investigated the effect of in vitro dilution of blood with saline on whole blood coagulation as measured by the thrombelastogram (TEG). ⋯ The r time, k time and r + k time were decreased relative to control in both diluent groups. The alpha angles were increased compared with control in both groups while maximum amplitude was unchanged in the Haemaccel diluted group. We conclude that haemodilution per se increases the coagulability of whole blood in vitro, but that saline haemodilution has a more marked effect on final clot strength.
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Randomized Controlled Trial Comparative Study Clinical Trial
Recovery after desflurane anaesthesia in the infant: comparison with isoflurane.
We have studied 20 infants, aged 2.5-8 weeks, undergoing general anaesthesia for pyloromyotomy with either desflurane or isoflurane. Patients were anaesthetized with equivalent 1 MAC values for age and agent. A blinded observer recorded times to breathing, swallowing, movement, extubation and side effects after discontinuation of the agent. ⋯ In addition, postoperative apnoea was documented in the isoflurane group but not in those infants receiving desflurane. There was no laryngospasm after extubation in either group. We conclude that desflurane possesses useful characteristics for recovery conditions in the infant and may be particularly useful in the ex-premature infant prone to apnoea and ventilatory depression.
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Randomized Controlled Trial Clinical Trial
Effect of neuromuscular block on depth of anaesthesia as measured by the auditory evoked response.
In a double-blind, randomized, controlled, prospective study, we have investigated the effects of vecuronium and laryngoscopy on the auditory evoked response (AER) of the electroencephalogram (EEG) in 40 ASA I and II patients under steady state anaesthesia. After stable anaesthesia had been achieved with 1.0 MAC of isoflurane and nitrous oxide in oxygen, patients were allocated randomly to receive two separate doses of vecuronium 0.05 mg kg-1 or saline. The AER was recorded before and after each dose and then after 20-s laryngoscopy in each group to determine any changes in the early cortical components of the AER waveform (Pa and Nb). ⋯ There were correspondingly significant haemodynamic responses to laryngoscopy in both groups. We conclude that neuromuscular block with vecuronium does not affect depth of anaesthesia as measured by the AER in either stimulated or unstimulated patients. In addition, we have demonstrated clearly the arousal effect of laryngoscopy on the AER.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of the pharmacodynamics and pharmacokinetics of an infusion of cis-atracurium (51W89) or atracurium in critically ill patients undergoing mechanical ventilation in an intensive therapy unit.
We have studied 12 critically ill, sedated patients who required a neuromuscular blocking drug to assist mechanical ventilation in an intensive care unit. Patients were randomized to receive an infusion of cis-atracurium 0.18 mg kg-1 h-1 (group 1, n = 6) or atracurium 0.6 mg kg-1 h-1 (group 2, n = 6) preceded, if necessary, by a bolus dose of 2 x ED95 of the same drug (cis-atracurium 0.1 mg kg-1 or atracurium 0.5 mg kg-1). Neuromuscular block was monitored using an accelerograph and the infusion rate adjusted regularly so that it was possible to detect the first response to train-of-four (TOF) stimulation of the ulnar nerve at the wrist. ⋯ Using the NONMEM program, a single compartment pharmacokinetic model was fitted to the plasma concentrations of cis-atracurium and the cis-cis, cis-trans and trans-trans isomers of atracurium. The mean population pharmacokinetic values for cis-atracurium were: volume of distribution (V) = 21,900 (SEM 416) ml; clearance (Cl) = 549 (79) ml min-1; half-life (T1/2) = 27.6 (3.6) min; and for the three groups of atracurium isomers were: cis-cis, V = 15,100 (720) ml, Cl = 449 (42) ml min-1, T1/2 = 23.4 (1.2) min; cis-trans, V = 18,000 (667) ml, Cl = 1070 (43) ml min-1, T1/2 = 11.7 (0.1); trans-trans, V = 13,100 (1280) ml, Cl = 1560 (55) ml min-1, T1/2 = 5.8 (0.4) min. Plasma laudanosine concentrations were lower in the cis-atracurium (peak value 1.3 micrograms ml-1) than in the atracurium (maximum 4.4 micrograms ml-1) group.