イソフルラン
イソフルランは獣医療で広く使用されている**吸入全身麻酔薬**です。 主な臨床的特徴： - **心血管系の安全性**：ハロタンなどの古い薬剤と比較して、心筋抑制やカテコールアミン感作作用が少ないです。 - **臓器の安全性**：肝代謝がごくわずか（約0.17%）であるため、肝疾患や腎疾患を持つ患者にも安全な選択肢です。 - **臨床のポイント**：セボフルランなどの新しい薬剤は麻酔深度の変更が早く、マスク導入がスムーズですが、イソフルランは依然として信頼性が高く、費用対効果に優れた獣医麻酔の定番です。
作用機序: The exact mechanism of inhalant anesthetics remains partially understood, but they are believed to act on the **lipid matrix of neuronal membranes** and interact with various ligand-gated ion channels (e.g., **GABA_A receptors**) in the brain and spinal cord. Key physiological effects: - **CNS**: Reversible depression, altered temperature regulation, increased cerebral blood flow. - **Cardiovascular**: Dose-dependent hypotension (primarily via **vasodilation** rather than direct myocardial depression). - **Respiratory**: Dose-dependent respiratory depression. > **MAC (Minimum Alveolar Concentration)** values: Dog = 1.5%; Cat = 1.2%; Horse = 1.31%.
動物種別の用量
- Anesthesia · 5% induction; 1.5-2.5% maintenance · Inhalation · Continuous · As needed · Concentrations are dependent upon fresh gas flow rate
- Anesthesia · 0.5-3%, inhaled · Inhalation · Continuous · As needed
- Maintenance of surgical anaesthesia · MAC is approximately 1.6% · Inhalational · Continuous · Duration of surgery · Adjust based on individual requirement and premedication.
- Anesthesia · Starting isoflurane at 1-2% · Inhalation · Continuous · As needed · After premed with medetomidine. Use a non-rebreathing system.
- Anesthesia · 4% · Inhalation · Continuous · As needed · Small birds can be anesthetized safely in 15-30 seconds
- Anesthesia · Induction occurs within 1-2 minutes at a concentration of 3-5%. Maintenance at 1.5-2% · Inhalation · Continuous · As needed · Anesthetic of choice for birds. Recovery is very rapid.
- Anesthesia (Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas) · Induction: 2-3%, maintenance: 0.25-2% · Inhalation · Continuous · As needed · Using a non-rebreathing system
- Anesthesia · Give 5% isoflurane and oxygen in a clear plastic bag or induction chamber. Maintenance levels are 3-5% (if isoflurane used alone). · Inhalation · Continuous · As needed · Induction time may take 30-60 minutes. Can be shortened with ketamine premedication.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- History or predilection towards malignant hyperthermia
- Known susceptibility to malignant hyperthermia
有害事象
- Dose-related hypotension
- Respiratory depression
- Nausea and vomiting
- Ileus
- Minimal cardiodepression
- Rare arrhythmias
- Dose-dependent hypotension (due to vasodilation, particularly in skeletal muscle)
- Dose-dependent respiratory depression
- Arrhythmias (less arrhythmogenic than halothane, but possible under certain conditions)
- Hypothermia
薬物相互作用
- Aminoglycosides · Additive neuromuscular blockade may occur
- ACE Inhibitors or Hypotensive Agents · Concomitant use may increase risks for profound hypotension
- Lincosamides · Additive neuromuscular blockade may occur
- Non-depolarizing Neuromuscular Blocking Agents · Additive neuromuscular blockade may occur · moderate
- Succinylcholine · May induce increased incidences of cardiac effects (bradycardia, arrhythmias) and malignant hyperthermia in susceptible patients
- Sympathomimetics (dopamine, epinephrine, etc.) · May result in arrhythmias, though isoflurane sensitizes the myocardium less than halothane. Use with caution and intensive monitoring.
- Sedatives (e.g., alpha-2 agonists, phenothiazines) · Reduces the concentration of isoflurane required to achieve surgical anaesthesia (MAC reduction). · moderate
- Opioid agonists · Reduces the concentration of isoflurane required to achieve surgical anaesthesia (MAC reduction). · moderate
- Nitrous Oxide (N2O) · Reduces the concentration of isoflurane required to achieve surgical anaesthesia. · moderate
モニタリング
- Respiratory and ventilatory status
- Cardiac rate and rhythm
- Blood pressure (particularly in 'at risk' patients)
- Level of anesthesia
- Respiratory rate, rhythm, and depth (capnography/ETCO2 recommended)
- Heart rate and rhythm (ECG)
- Blood pressure (Doppler or oscillometric)
- Oxygen saturation (Pulse oximetry/SpO2)
- Body temperature
- Anaesthetic depth (eye position, palpebral reflex, jaw tone)
過量投与
Overdose risks are increased with intermittent positive pressure ventilation. Profound hypotension may occur, which usually responds to IV fluids but may require the use of vasopressors.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。