British journal of anaesthesia
-
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.
-
Randomized Controlled Trial Comparative Study Clinical Trial
Clinical comparison of atracurium and vecuronium (Org NC 45).
The potency, histamine releasing ability, cardiovascular effects, and pharmacodynamics of vecuronium and atracurium were investigated in 64 healthy patients following administration i.v. Cumulative dose-response curves showed vecuronium to be 4.4 times as potent as atracurium. Using the calculated ED90 of each drug (43 micrograms kg-1 for vecuronium and 188 micrograms kg-1 for atracurium), vecuronium had a significantly more rapid onset time and shorter duration of action than atracurium. ⋯ There was no clinical evidence of histamine release during the study. No clinically significant changes in arterial pressure or heart rate were seen after the injection of either drug, although vecuronium caused a statistically significant decrease in heart rate (approximately 5%) at 5 and 10 min after administration. Both drugs would appear to have certain advantages over existing non-depolarizing neuromuscular blocking drugs.
-
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.