British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Sedation for fibreoptic gastroscopy: a comparative study of midazolam and diazepam.
Midazolam, a water-soluble benzodiazepine, was compared with diazepam in fat emulsion (Diazemuls) as sedation for outpatient gastroscopy in a randomized double-blind fashion. Midazolam 0.05 mg kg-1 was found to be approximately equipotent to Diazemuls 0.15 mg kg-1. There were no differences concerning speed of recovery and all patients were considered ready for discharge after 2 h. ⋯ With the same degree of sedation, midazolam produced a higher frequency of amnesia (60% v. 7%; P less than 0.001) for the endoscopic procedure. Although the patients appeared to prefer midazolam to Diazemuls, this difference was significant only in patients who had not previously undergone gastroscopy (P less than 0.05). The high degree of amnesia with midazolam may be an advantage in sedation for unpleasant procedures like gastroscopy.
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This article reviews the actions of general anaesthetics on synapses in the mammalian central nervous system. It is shown that during general anaesthesia, anaesthetics act primarily on the chemical transmission process itself and do not affect the conduction of impulses in nerve axons or change the electrical excitability of neurones. ⋯ In addition to these effects on the neurosecretory process, anaesthetics directly affect the sensitivity of the postsynaptic receptors to transmitter substances, although the effects vary between anaesthetics and receptors. It is concluded that general anaesthesia results from a summation of a number of effects which together tend to depress the excitability of the CNS as a whole.
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The differential sensitivities of A beta, A delta and C fibres of rat vagus nerve to bupivacaine, etidocaine and AL-381 were studied in vitro. In A beta fibres, at 35-37 degrees C, 50 mumole litre-1 of the drugs had similar effects on the action potential amplitude, while at greater concentrations (100 and 200 mumole litre-1) the greatest mean depression of amplitude was seen with etidocaine (n.s.). ⋯ Etidocaine 100 mumole litre-1 was more depressant than the same dose of bupivacaine. The C fibres were blocked most rapidly by AL-381, while etidocaine had the least effect.