Изофлуран

Химические свойства

colourless liquid

Использование

Isoflurane is a halogenated ether used for inhalational anesthesia. Recent studies suggest that there might be a relationship between administration of isoflurane and postoperative cognitive dysfunct ion (POCD).

Биологические функции

Isoflurane (Forane) is a structural isomer of enflurane and produces similar pharmacological properties: some analgesia, some neuromuscular blockade, and depressed respiration. In contrast, however, isoflurane is considered a particularly safe anesthetic in patients with ischemic heart disease, since cardiac output is maintained, the coronary arteries are dilated, and the myocardium does not appear to be sensitized to the effects of catecholamines. Also, blood pressure falls as a result of vasodilation, which preserves tissue blood flow. Isoflurane causes transient and mild tachycardia by direct sympathetic stimulation; this is particularly important in the management of patients with myocardial ischemia.
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.

Общее описание

Isoflurane is a volatile liquid (bp＝48.5°C) with an MAC of1.15, a blood:gas partition coefficient of 1.43 and high solubilityin fat. Isoflurane is a structural isomer of enflurane. Itis a known respiratory irritant, but less so than desflurane.Approximately 0.2% of the administered drug undergoesmetabolism, the rest is exhaled unchanged. The metabolismof isoflurane yields low levels of the nephrotoxic fluoride ionas well as a potentially hepatotoxic trifluoroacetylating compound). The relatively low concentrations ofthese compounds have resulted in very low risks of hepatotoxicityand nephrotoxicity. There have been no reports ofseizures caused by isoflurane and only transient increases inheart rate have been reported.

Клиническое использование

Isoflurane was introduced in the United States in 1981 and is a potent anesthetic agent with many similarities to its isomer enflurane (potent, nonflammable, and intermediate blood solubility). It does produce significantly fewer cardiovascular effects than enflurane, however, and it can be used safely with epinephrine without as great a concern for arrhythmia production. Isoflurane has a more pungent odor than halothane and, thus, can cause irritation to the throat and respiratory tract, triggering coughing and laryngospasm. To overcome this problem, it often is supplemented with intravenous agents. Less than 0.2% of an administered dose is metabolized, mostly to fluoride and trifluoroacetic acid. Some minimal potential for hepatotoxicity is associated with a trifluoroacetyl halide metabolite.