丙泊酚
丙泊酚是一種短效、高脂溶性的靜脈麻醉劑,在獸醫學中廣泛用於全身麻醉的誘導與維持。由於其起效迅速且恢復平穩,特別適用於門診診斷或小型手術。 **主要臨床特徵:** * **起效與恢復迅速:** 在30-60秒內誘導麻醉;由於藥物從中樞神經系統重新分佈至其他組織,恢復通常平穩且快速。 * **器官功能:** 對於患有輕至中度心臟疾病、肝臟或腎臟疾病的動物使用安全。 * **標示外使用:** 常以連續靜脈輸注 (CRI) 用於難治性癲癇重積狀態,特別是在肝性腦病等禁用戊巴比妥的情況下。 * **貓的注意事項:** 貓缺乏狗所具備的強效葡萄糖醛酸結合代謝途徑,因此在連續每日使用或長時間輸注時,容易出現恢復延長、海因茲小體貧血 (Heinz body anemia) 及不適感。 > **臨床要點:** 丙泊酚**不具備鎮痛作用**。對於會產生疼痛的處置,必須合併使用適當的圍手術期鎮痛方案(如鴉片類藥物、非類固醇消炎藥、局部麻醉阻斷)。
作用機制: While the monograph notes the mechanism is not well understood, **modern pharmacological consensus** indicates that propofol primarily acts as a positive allosteric modulator of inhibitory **GABA_A receptors** in the central nervous system. * **Mechanism:** Propofol binds to GABA_A receptors → increases the inward conductance of chloride ions → hyperpolarizes the postsynaptic neuronal membrane → profound CNS depression and hypnosis. * **Cardiovascular & Respiratory:** Causes dose-dependent direct myocardial depression, vasodilation (arterial hypotension), and significant respiratory depression (apnea is common with rapid boluses). * **Other Effects:** Decreases intraocular pressure (IOP), possesses antiemetic properties, and at sub-anesthetic doses, can act as an appetite stimulant in dogs.
各物種劑量
- Induction of general anesthesia (no premedication) · 4.1-8 mg/kg · IV · titrated · Mean induction dose 7.4 mg/kg.
- Induction of general anesthesia (with premedication) · 2.7-8 mg/kg · IV · titrated · Dose sparing effect of 16-24%.
- Maintenance of general anesthesia (no premedication) · 0.8-5 mg/kg · IV · intermittent · Duration of anesthesia following each dose is approx 3-5 minutes.
- Single injection induction (with acepromazine +/- butorphanol) · 4-6 mg/kg · IV · single dose · Doses of 8-13 mg/kg IV allow intubation without topical anesthesia.
- Induction of anaesthesia (unpremedicated) · 8 mg/kg · IV · single dose · as needed · Administer slowly over 30-60 seconds. Titrate to effect.
- Induction of anaesthesia (premedicated) · 2-5 mg/kg · IV · single dose · as needed · Administer slowly over 30-60 seconds. Titrate to effect.
- Maintenance of anaesthesia · 0.1-0.4 mg/kg/min · IV · CRI · as needed · Likely to result in a prolonged recovery in cats. Dose depends on other agents given in combination. Do not use benzyl alcohol formulations for CRI.
- Anesthesia (Rabbits) · 5-14 mg/kg slow IV (20 mg/kg/minute) to effect · IV · titrated · Not recommended as the sole agent for maintenance.
- Anesthesia (Mice) · 26 mg/kg · IV · single dose
給藥途徑
禁忌症
- Hypersensitivity to propofol or any component of the product
- Patients where general anesthesia or sedation is strictly contraindicated
- Use of benzyl alcohol-preserved formulations for maintenance of anaesthesia via continuous rate infusion (CRI)
不良反應
- Transient respiratory depression and apnea (especially with rapid IV administration)
- Arterial hypotension and bradycardia
- Cyanosis (secondary to apnea)
- Seizure-like clinical signs during induction (paddling, opisthotonus, myoclonic twitching)
- Histamine release and rare anaphylactoid reactions
- Cats (with repeated/prolonged use): Heinz body anemia, slowed recovery, anorexia, lethargy, diarrhea
- Apnoea (especially with rapid injection)
- Cyanosis
- Bradycardia
- Severe hypotension
- Muscle rigidity and tremors (dogs)
- Paradoxical muscle movements (dogs)
- Heinz body anaemia (cats, with repeated daily use)
- Pain on IV injection
藥物相互作用
- Inhalation Anesthetics (halothane, isoflurane) · Propofol serum concentrations may be increased; propofol induction may require higher initial inhalant concentrations due to rapid recovery.
- Local Anesthetics · Propofol dosage requirements for sedation or hypnosis may be reduced.
- Anticholinergics · Propofol-induced bradycardia may be exacerbated, particularly when opiate premedicants are used.
- Chloramphenicol · May decrease clearance of propofol and increase recovery times.
- Clonidine · When used as a premed, may reduce propofol dosage requirements.
- CNS Depressants (acepromazine, diazepam, etc.) · Increased sedative, anesthetic, and cardiorespiratory depression possible; propofol dose should generally be reduced by ~25%.
- Hepatic P-450 Inhibitors (cimetidine, ketoconazole) · May potentially increase recovery times associated with propofol (especially significant in cats).
- Fentanyl · Increased risk for bradycardia.
- Medetomidine · Hypoxemia may occur when propofol is used after medetomidine; dosage adjustments and adequate monitoring required.
- Metoclopramide · May reduce the propofol dose required for induction by 20-25%.
- Midazolam · Synergistic effects; midazolam plasma concentrations may be increased up to 20%.
監測
- Level of anesthesia/CNS effects
- Respiratory rate, rhythm, and depth (monitor for apnea/cyanosis)
- Cardiovascular status (cardiac rate/rhythm, blood pressure, pulse oximetry)
- Respiratory rate, rhythm, and depth (capnography recommended)
- Heart rate and rhythm (ECG)
- Blood pressure
- Oxygen saturation (SpO2)
- Depth of anaesthesia
過量
Overdosages are likely to cause **significant respiratory depression** (apnea) and potentially severe **cardiovascular depression** (hypotension, bradycardia). **Treatment:** 1. Immediately discontinue propofol administration. 2. Establish an airway and provide **artificial ventilation with 100% oxygen**. 3. Administer symptomatic and supportive treatment for cardiovascular depression (e.g., intravenous fluid therapy, vasopressors, anticholinergics like atropine or glycopyrrolate).
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