Isoflurane cardiovascular effects

Cardiovascular effects. Anaesthetic concentrations of isoflurane, i.e. 1-1.5 MAC, cause only a slight impairment of myocardial contractility and stroke volume and cardiac output is usually maintained... 

Sevoflurane is a chemical analogue of isoflurane. It is less chemically stable than the other volatile anaesthetics in current use. About 3% is metabolised in the body and it is degraded by contact with carbon dioxide absorbents, such as soda lime. The reaction with soda lime causes the formation of a vinyl ether (Compound A), which may be nephrotoxic. Sevoflurane is less soluble than isoflurane and is very pleasant to breathe, which makes it an excellent choice for inhalational induction of anaesthesia, particularly in children. The respiratory and cardiovascular effects of sevoflurane are very similar to isoflurane. 

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Cardiovascular effects Most inhaled anesthetics decrease arterial blood pressure moderately. Enflurane and halothane are myocardial depressants that decrease cardiac output, while isoflurane causes peripheral vasodilation. Nitrous oxide is less likely to lower blood pressure than are other inhaled anesthetics. Blood flow to the liver and kidney is decreased by most inhaled agents. Halothane may sensitize the myocardium to the arrhythmogenic effects of catecholamines. 

Unlike enflurane, isoflurane does not produce a seizurelike EEG pattern. Furthermore, the metabolic transformation of isoflurane is only one-tenth that of enflurane, so fluoride production is quite low. Among the halogenated hydrocarbons, isoflurane is one of the most popular, since it preserves cardiovascular stability and causes a low incidence of untoward effects. 

Isoflurane has a dose-dependent depressant effect on the myocardium. In vitro studies indicate that it reduces myocardial contractility to a similar extent as halothane. In vivo, isoflurane appears to be less of a cardiovascular depressant than other volatile agents. 

Inhaled anesthetics change heart rate either directly by altering the rate of sinus node depolarization or indirectly by shifting the balance of autonomic nervous system activity. Bradycardia is often seen with halothane, probably through vagal stimulation. In contrast, enflurane, and sevoflurane have little effect, and both desflurane and isoflurane increase heart rate. In the case of desflurane, cardiovascular responses include a transient sympathetic activation that can lead to marked increases in heart rate and blood pressure when high inspired gas concentrations are administered. 

Cardiovascular System The hypotensive effect of sevoflurane primarily is due to systemic vasodilation, although sevoflurane also produces a concentration-dependent decrease in cardiac output. Unlike isoflurane or desflurane, sevoflurane does not produce tachycardia and thus may be a preferable agent in patients prone to myocardial ischemia. 

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