Articles: anesthetics.
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Information derived from measurements of blood concentrations of local anaesthetics can be extended by the application of pharmacokinetic anaylsis. A better understanding of quantitative aspects of the disposition and absorption of these drugs should assist the anaesthetist in deciding the optimal agent and dosage for regional block techniques.
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Comparative Study
Evaluation of clinical tolerance of local anaesthetic agents.
The clinical tolerance to local anaesthetic drugs can be assessed from a knowledge of their pharmacokinetic behaviour, their absorption properties and the effects produced by controlled i.v. infusions. Pharmacokinetic behavior can be calculated from the plasma concentrations of the drugs injected i.v. in non-toxic doses. Absorption properties can likewise be determined from plasma concentrations following injection at various sites. ⋯ Such dosage is considerably affected by the rate of injection. The venous plasma concentrations at the height of toxicity are unreliable guides to toxicity. Experiences using the new local anaesthetic etidocaine are reported.
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Recent Adv Stud Cardiac Struct Metab · Jan 1975
Effects of inhalation anesthetics on cardiac function and metabolism in the intact dog.
In healthy, closed-chest dogs, dose-dependent depression of ventricular function was produced by the anesthetics halothane, methoxyflurane, and fluroxene, as evidence by decreases in left venticular stroke volume, stroke work, dP/dt, and an increased enddiastolic pressure. Myocardial blood flow and oxygen consumption decreased concomitantly and were correlated with aortic blood pressure decreases. ⋯ The hemodynamic effects of halothane and methoxyflurane are similar to those previously reported in man, but those of fluroxene are different. Consequently, clinical speculation from these results is not justified at this time.
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The biotransformation of clinically important ester- and amide-type local anesthetic agents is reviewed with emphasis on their fate in man. Aspects considered include: 1 degree the contribution of biotransformation to overall pharmokinetic profiles and systemic safety; 2 degrees the effect of disease on biotransformation; 3 degrees biotransformation and fate in the neonate; 4 degrees pathways and products of biotransformation; 5 degrees pharmacokinetics of metabolites; 6 degrees pharmacological activity and toxicity of metabolites.
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Comparative Study Clinical Trial Controlled Clinical Trial
Evaluation of the toxicity of local anaesthetic agents in man.
Etidocaine given by intravenous infusion has been compared, using a double-blind technique, with bupivacaine and lignocaine in respect of toxic symptoms and signs. The degree of toxicity is affected considerably by the rate of drug infusion. At 10 mg/min subjects could tolerate twice the dose of etidocaine as bupivacaine. ⋯ Lignocaine at 20 mg/min was better tolerated than etidocaine. Venous plasma concentration during these experiments showed a more rapid decrease in the case of etidocaine compared with bupivacaine, but the concentrations were unhelpful in predicting the toxic effects. Similarly electroencephalography revealed no abnormalities in spite of marked subjective and objective signs of toxicity.