Articles: anesthetics.
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Acta Anaesthesiol Scand · Jan 1977
Comparative StudyHypoxia-induced vasoconstriction in isolated perfused lungs exposed to injectable or inhalation anesthetics.
Investigations during the last two decades have revealed a tendency to inpaired pulmonary gas exchange in patients during general anesthesia. In the awake state, arterial hypoxemia is counteracted by a mechanism which tends to normalize the ventilation/perfusion ratio of the lungs by way of a hypoxia-induced vasoconstriction in poorly ventilated areas. This results in a redistribution of perfusion to more adequately ventilated lung regions. ⋯ The experiments showed that the response was unaffected by N2O and injectable anesthetics, while a reversible, dose-dependent damping effect was demonstrated for the volatile inhalation anesthetics, ether, halothane and methoxyflurance. The effect could be demonstrated at blood concentrations comparable to those used in clinical anesthesia, and it was not due to a general paralysis of the vascular smooth muscle. The findings might, at least in part, explain the occurrence of arterial hypoxemia during general inhalation anesthesia.
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This study assesses the effects of agents commonly used in anaesthesia on enflurane-induced seizure threshold and on established seizure activity, during steady state enflurane anaesthesia. EEG seizure activity was monitored in cats from chronic cortical and subcortical recording sites. Diazepam, thiopentone, methohexitone and ketamine all enhanced established EEG seizure challenge. ⋯ The effects of these intravenous agents on established enflurane seizure patterns exceeded in duration the expected EEG effect of the agent when used alone. The limited number of experiments, however, precluded statistical verification of our findings. The similarities between centrencephalic minor motor seizures and enflurane seizure pattern in terms of EEG and convulsive expression, including drug response, are noted.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparative anaesthetic properties of various local anaesthetic agents in extradural block for labour.
Various concentrations of lignocaine, etidocaine and bupivacaine in 10-ml doses of plain solutions were studied in a double-blind manner as agents for extradural analgesia to relieve the pain of labour. In 67 patients in established labour the onset time and duration of analgesia were assessed by the abolition and recurrence of the pain of uterine contractions, motor block on a 0-2 scale, dermatomal spread by pinprick testing, and arterial pressure by standard sphygmomanometry. Increasing the drug concentration reduced the onset times and increased both the duration of analgesia and the degree of motor block, but had little effect on dermatomal spread or on the frequency of hypotension. Based on the results the agents have been classified with regard to onset and duration of analgesia and degree of motor blockade.