British journal of anaesthesia
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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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After extradural blockade failed to extend sufficiently for elective Caesarean section, spinal anaesthesia was performed using 1.6 ml of hyperbaric 0.5% bupivacaine solution in 8% glucose (Marcain Heavy). The patient rapidly developed sensory blockade to the level of T2, and became distressed and dyspnoeic. ⋯ Despite i.v. ephedrine and fluid loading, severe hypotension occurred, which responded subsequently to further doses of ephedrine and infusion of colloid. A healthy infant was delivered by Caesarean section.
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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 continuous paravertebral and extradural infusions of bupivacaine for pain relief after thoracotomy.
Pain was controlled in 20 post-thoracotomy patients using a continuous infusion of 0.25% bupivacaine through an extradural or para-vertebral catheter. Both techniques provided good analgesia. Hypotension and urine retention occurred significantly less frequently in the paravertebral than in the extradural group.