British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Influence of suxamethonium on the action of subsequently administered vecuronium or pancuronium.
The effects of suxamethonium were studied on the onset time and duration of action of vecuronium or pancuronium in 45 adult patients anaesthetized with halothane and nitrous oxide. After an intubating dose of suxamethonium, the force of the evoked twitch returned to a value greater than control. The onset of the reduction in force produced by subsequent administration of vecuronium or pancuronium was faster and recovery slower. This potentiating effect of suxamethonium persisted for at least 2 h.
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The actions of alcuronium, vecuronium and tubocurarine have been studied in the isolated forearms of six healthy, non-anaesthetized volunteers. The responses of adductor pollicis were measured during onset and recovery of neuromuscular block for each agent. There was a drug-related disparity between mechanomyogram (MMG) and electromyogram (EMG) measurement of the first response of the train-of-four (T1) and of the ratio of the fourth (T4) to the first response (TOF ratio). ⋯ Analysis of variance of the differential fade loops failed to show a drug-related effect. We conclude that care should be taken in assuming interchangeability between MMG and EMG measurement of T1. Relationships between T1 and TOF ratio derived during recovery do not necessarily apply during onset and may lead to error in estimating the degree of muscle relaxation.
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We present a new pattern of nerve stimulation--double burst stimulation (DBS)--to detect residual neuromuscular block manually. The DBS consists of two short lasting, 50-Hz tetanic stimuli or bursts separated by a 750-ms interval. The response to this pattern of stimulation is two single separated muscle contractions of which the second is less than the first during nondepolarizing neuromuscular blockade. ⋯ The DBS with three impulses in each burst (DBS3,3) was considered to be the most sensitive and the least painful and thus most suitable for clinical use. The degree of fade in TOF and DBS3,3 was almost identical at any level of blockade (correlation coefficient 0.96), and the major post-DBS3,3 effect was a depression of the first twitch in TOF lasting less than 15 s. It is concluded that the DBS is more sensitive than the TOF in manual detection of residual block.
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We have assessed a Venturi driven device for delivering continuous positive airway pressure (CPAP) using a reservoir bag and expiratory valve under conditions of continuous flow and simulated spontaneous breathing. The system performed well and was economical, consuming only 3.5 litre min-1 of fresh gas. One Venturi was partially blocked and performed inadequately, but the function of a second one was close to the manufacturer's specification (inspired oxygen 33%, flow 20 litre min-1 against end-expiratory pressures of 0-1.8 kPa). ⋯ The characteristics of the expiratory valve approached those of a threshold resistor. Small fluctuations in airway pressure occurred at all settings of CPAP and decreased with the increasing compliance of the circuit at higher values of CPAP. The method provided to monitor the airway pressure was inaccurate and overestimated the true pressure by 20% at pressures greater than 1 kPa.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of 1.5% enflurane with 1.25% isoflurane in oxygen for caesarean section: avoidance of awareness without nitrous oxide.
We examined the feasibility of administering nearly 100% oxygen throughout the induction-delivery period of general anaesthesia for 113 Caesarean sections. Isoflurane 1.25% was compared with 1.5% enflurane for maintenance of anaesthesia. ⋯ The three main criteria for a satisfactory general anaesthetic technique for Caesarean section were fulfilled, namely no maternal awareness, no undue depression of the fetus and no adverse effect on uterine contractility. Isoflurane and enflurane appear to be suitable anaesthetic agents for facilitating hyperoxygenation during Caesarean section.