British journal of anaesthesia
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Recent advances in the physiology of cardiovascular reflexes, with special reference to hypotension.
The basic response of the carotid and aortic baroreceptor areas to pressure stimuli has been known for some years (Heymans and Neil, 1958); stimulation of these areas (acute hypertension) leads mainly to bradycardia and hypotension; reduction in receptor activity (acute hypertension) results in an increase in heart rate and an increase in arterial pressure. In this review, comments have been made on the inadequacy of the "control theory" approach in describing the details of such mechanisms. Some recent evidence is presented of the differences between the effects from stimulation of the carotid and aortic areas, of the modifying influences of efferent sympathetic nerves to the two receptor areas, and of some evidence for central nervous "control" of the reflexes. The responses of the reflexes in the complex situation of haemorrhage, together with possible reflex actions from the ventricles, are discussed.
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Randomized Controlled Trial Comparative Study Clinical Trial
Effect of intercostal nerve blockade during operation on lung function and the relief of pain following thoracotomy.
The use, during operation, of intercostal nerve blocks with lignocaine and bupivacaine for the relief of pain following thoracotomy was assessed in 138 patients. Irrespective of the method used to evaluate efficacy, it was not possible to demonstrate a lasting effect of clinical significance favouring either local anaesthetic agent. This form of treatment, although free from serious side effects, had no beneficial effects on lung function and is not recommended for the relief of pain following surgery.
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Ten intact anaesthetized dogs breathing room air spontaneously (Group A) were compared with ten artificially ventilated dogs (Group B). All were given a bolus of ketamine 2 mg/kg followed by a 20-min infusion of ketamine 0.1 mg/kg/min. In Group A, coronary sinus blood flow, measured with a thermodilution flowmeter, increased by 90% while coronary vascular resistance decreased by 28% and coronary sinus oxygen content decreased by 27%. ⋯ A dose of 8 mg/kg produced increases in cardiac output, heart rate and arterial pressure of 21%, 44% and 24%, respectively, while coronary blood flow increased 47%. We conclude that, in healthy dogs, ketamine produces an increase in heart rate and cardiac work. A significant increase in coronary blood flow appears to be insufficient to meet the metabolic demands of the myocardium, as the coronary sinus oxygen content decreased.