Selection Of Anaesthetic Drugs: Halothane, Isoflurane Or Sevoflurane
吸入麻醉藥的選擇：氟烷、異氟烷、七氟烷
Speed of Induction and Recovery誘導與蘇醒速度
Sevoflurane is half as soluble in blood as isoflurane, which is approximately half as soluble in blood as halothane. The more insoluble an anaesthetic, the faster the anaesthetic induction, more rapid the changes in depth and faster the recovery. Clinically the difference between these agents is not huge, but animals will recover fastest from sevoflurane and to a lesser degree, isoflurane, and will be more alert - owners notice this difference! Speed of recovery is an important consideration for neonates (C-sections), geriatric patients and for long anaesthetics.
七氟烷的血液溶解度是異氟烷的一半，也是氟烷的將近一半。溶解度越低，誘導、麻醉變深或者蘇醒的速度越快。臨床上這幾種藥區別不大，但是與異氟烷相比，使用七氟烷的動物會更加快速地蘇醒到更清醒的程度，這將需要寵物主人更加關注這種不同。對于剖腹產或者年老的病號，蘇醒的速度非常重要。同樣，時間長的手術蘇醒速度也很重要。
Circulatory Function循環功能
All inhalation anaesthetics cause a dose-dependent reduction in mean arterial pressure which is caused by a dose-dependent decrease in cardiac output and stroke volume. There is a tendency for less cardiac depression with isoflurane and sevoflurane, particularly in cats, and at deeper levels of anaesthesia. The cardiovascular system seems to be more tolerant of changes in anaesthetic depth with isoflurane or sevoflurane compared to halothane.
所有的吸入麻醉劑都會引起劑量依賴性的平均動脈壓下降，這是因為有劑量依賴性的心臟輸出降低和每搏輸出量降低。這種趨勢，特別在是貓身上或者是在更深的麻醉的時候，在用異氟烷或者七氟烷的時候更不明顯。
The arrhythmogenic potential for halothane is much greater than that for isoflurane- or sevoflurane. This is especially important for any patient with cardiac disease manifested by an arrhythmia. In such patients (e.g., gastric dilata-tion), halothane may be contraindicated.
氟烷相對于異氟烷和七氟烷，更容易引起心率失常。這對于已經有心率失常的心臟病的病號特別重要。
Respiratory Function呼吸功能
All inhalation anaesthetics cause a dose-dependent respiratory depression, as evidenced by a rise in arterial carbon dioxide tension with increasing anaesthetic dose. In canine patients, isoflurane tends to produce the most respiratory depression when compared to the other inhalation agents. However, in cats, isoflurane has been shown to cause less respiratory depres-sion when compared to halothane (there is no comparative data for sevoflurane).
所有的呼吸麻醉藥都會引起劑量依賴性的呼吸抑制，因為增加麻醉劑量的時候動脈二氧化碳含量會呈增加的趨勢就能證明如此。在犬的病例上，異氟烷的呼吸抑制作用比其他麻醉劑要強。盡管如此，在貓身上異氟烷的呼吸抑制作用比氟烷要低。
Metabolism代謝作用
Traditionally, it was thought that the inhalation anaesthetics were entirely taken up and eliminated by the lungs. However, of that portion of the anaesthetic taken up by the body's tissue, 25% of halothane is metabolized, compared to 3% of sevoflurane and virtually O% for isoflurane This becomes particularly important for neonatal animals and animals with liver or renal impairment.
傳統認為吸入麻醉劑是由肺部吸收和排出的。但是，有部分麻醉劑由身體組織吸收，其中25%氟烷由身體代謝，3%七氟烷、幾乎是0%異氟烷由身體代謝。這對于新生動物或者有肝腎功能損傷的動物非常重要。
In addition, metabolism of inhalation anaesthetics is an important concern from an occupational health aspect. Since metabolism of isoflurane, and to a lesser extent sevoflurane, is minimal, it offers distinct advantages from the perspective of occupational health exposure. In veterinary practices with good waste anaesthetic gas management, occupational exposure still occurs at the time of disconnection, during recovery and when servicing equipment!
另外，麻醉藥的代謝對職業健康非常重要。因為異氟烷的身體代謝比七氟烷低，這對于職業健康而言有很長遠的意義。如果對廢氣有很好的管理，獸醫臨床上職業暴露時間點是在拔管之后和在操作機器的時候。
Pregnant women should minimize their exposure to waste anaesthetic gases, particularly those that are highly metabolized such as halothane and nitrous oxide. AAS advises pregnant woman to wear face masks that scavenge waste anaesthetic gas while working in anaesthesia.
懷孕女性應當盡量避免接觸麻醉廢氣，特別是那些很大部分身體代謝的藥物例如氟烷和笑氣。AAS公司懷孕女性要在麻醉工作中戴上防毒面具。