硫噴妥鈉
硫噴妥鈉是一種超短效硫代巴比妥類藥物，主要用於全身麻醉的誘導或極短時間手術的單一麻醉劑。 **臨床要點：** * **重新分佈動力學：** 其作用時間短（10-30分鐘）是由於藥物從血流豐富的中樞神經系統快速重新分佈到肌肉和脂肪組織，而非快速代謝。 * **視覺獵犬敏感性：** 靈緹犬（格雷伊獵犬）及其他視覺獵犬由於代謝處理差異和體脂較低，恢復期會延長；通常建議使用其他誘導劑（如丙泊酚、阿法沙龍或美索比妥）。 * **組織毒性：** 硫噴妥溶液呈強鹼性（pH > 10）。**血管外漏出會導致嚴重的組織刺激和壞死。** 必須透過穩固的靜脈留置針給藥。 * **致心律不整性：** 它會使心肌對兒茶酚胺敏感，常在犬隻引起短暫的室性二聯律。
作用機制: Thiopental is a highly lipid-soluble thiobarbiturate. * **Mechanism:** It binds to the **GABA_A receptor** complex in the central nervous system. * **Pathway:** Binding → increases the duration of chloride ion channel opening → enhances chloride influx → hyperpolarization of the postsynaptic neuronal membrane → profound CNS depression, hypnosis, and anesthesia. * Due to its high lipid solubility, it rapidly crosses the blood-brain barrier, resulting in anesthesia within 15-30 seconds of IV injection.
各物種劑量
- Anesthesia · 9.9-15 mg/kg · IV · once · depending on depth required
- Anesthesia · 20-22 mg/kg · IV · once · Given after atropine (0.7 mg/kg) IM
- Anesthesia · 13.2-26.4 mg/kg · IV · once · depending on duration of anesthesia required
- Anesthesia (unpremedicated) · 22 mg/kg · IV · once
- Anesthesia (after tranquilization) · 15.4 mg/kg · IV · once
- Anesthesia (after narcotic premedication) · 11 mg/kg · IV · once
- Anesthesia induction · 12-15 mg/kg · IV · once · One-third administered rapidly, additional amount to effect
- Anesthesia · 8.14-15.4 mg/kg · IV · once
- Deep surgical anesthesia (unweaned calves fasted 6-12h) · no more than 6.6 mg/kg · IV · once
- Anesthesia (calves under 2 weeks of age) · 15-22 mg/kg · IV · once · 10-12 minutes · Administer slowly until complete muscular relaxation
給藥途徑
禁忌症
- Absence of suitable veins for IV administration (Absolute)
- History of hypersensitivity to barbiturates (Absolute)
- Status asthmaticus (Absolute)
- Preexisting leukopenia in horses
- Use with extreme caution or avoid in greyhounds and other sight hounds
- Relative: Severe cardiovascular disease, ventricular arrhythmias, shock, increased intracranial pressure, myasthenia gravis, severe hepatic disease
不良反應
- Ventricular bigeminy (dogs)
- Apnea (especially in cats)
- Arterial hypotension
- Excitement and severe ataxia during recovery (horses, if used alone)
- Transient leukopenia and hyperglycemia (horses)
- Vascular dilatation and hypoglycemia (with rapid IV administration)
- Severe tissue necrosis (if administered perivascularly)
- Prolonged recovery with repeated doses
藥物相互作用
- Clonidine · IV clonidine prior to induction may reduce thiopental dosage requirements by up to 37%
- CNS Depressants · May enhance respiratory and CNS depressant effects
- Diazoxide · Potential for hypotension
- Epinephrine / Norepinephrine · Ventricular fibrillatory effects may be potentiated when used with thiobarbiturates and halothane
- Metoclopramide · Given prior to induction may reduce thiopental dosage requirements
- Midazolam · May potentiate hypnotic effects
- Opiates · Given prior to induction may reduce thiopental dosage requirements
- Phenothiazines · May potentiate thiopental effects; hypotension possible
- Probenecid · May displace thiopental from plasma proteins
- Sulfonamides · Thiopental and sulfas may displace one another from plasma proteins
監測
- Level of hypnosis/anesthesia
- Respiratory status (rate, depth, apnea)
- Cardiac status (heart rate, rhythm, blood pressure)
過量
Treatment of thiobarbiturate overdosage consists of: * **Respiratory Support:** Provide oxygen (O2) and mechanical ventilation. * **Cardiovascular Support:** Provide IV fluids and supportive care. > **Note:** Do NOT use catecholamines (e.g., epinephrine) as they may induce fatal ventricular arrhythmias in the presence of thiobarbiturates.
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