Articles: anesthetics.
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A chronic model for investigation of spinal anesthesia in the dog is described. This model incorporates the use of a chronically implanted catheter in the lumbar subarachnoid space. An 18-gauge thin-walled Crawford needle is passes percutaneously into the subarachnoid space. ⋯ Durations of motor blockade were longest for dibucaine and tetracaine, followed in order of decreasing duration by bupivacaine, lidocaine, chloroprocaine, and mepivacaine. The durations of subarachnoid conduction motor blockades in the dog are qualitatively similar to reported values for spinal anesthesia in man. Therefore, the technique described may provide a useful model to evaluate factors that may influence spinal anesthesia.
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Comparative Study
Comparison of the chronotropic responses to local anesthetics (procaine, lidocaine, prilocaine, mepivacaine and bupivacaine) of the canine sinus node in situ.
Effects of local anesthetics (procaine, lidocaine, prilocaine, mepivacaine and bupivacaine) on the sinus node of the nerve-intact dog heart were studied in situ by means of selective perfusion of the sinus node through the sinus node artery. The agents caused a dose-dependent decrease in heart rate and the order of their potency in decreasing the heart rate was as follows, bupivacaine greater than lidocaine=mepivacaine=prilocaine greater than procaine. ⋯ Tetrodotoxin also prevented the positive chronotropic effect of procaine. From these results the following conclusion can be drawn: the negative chronotropic effects of these agents are induced mainly by a direct inhibitory action on the sinus node, and partly by blockade of sympathetic tone, and the interaction with the postganglionic adrenergic nerves plays an important role in the induction of the positive chronotropic responses to procaine and prilocaine.
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Review Clinical Trial
Investigations on isoflurane, sevoflurane and other experimental anaesthetics.
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Int Anesthesiol Clin · Jan 1981
ReviewRespiratory and cardiovascular responses to hypoxemia and the effects of anesthesia.
The normoxic ventilatory drive contributes to the normal level of ventilation, and the hypoxic ventilatory drive contributes to the maintenance of adequate gas exchange in the presence of ventilation/blood flow maldistribution and increased mechanical load to breathing. This respiratory drive arises principally from stimuli at the carotid chemoreceptors. The reflex cardiovascular responses to hypoxia also contribute to the delivery of O2 to vital organs, and their efficacy depends on the integrity of the respiratory response and the autonomic nervous system as well as the function of the vascular system. ⋯ Hence the patient in the perioperative period continues to have impaired respiratory response to hypoxemia. As anesthetic and surgical care extends to older patients, patients with systemic disease, and recipients of cardiovascular peripheral and central drugs, the clinical implications of the impairment of ventilatory and cardiovascular responses to hypoxia, and the maintenance of organ and system function, escalate. Only a few hesitant steps have been taken into this vast arena of clinical and experimental research.