Propofol
Propofol is a short-acting, highly lipophilic intravenous anesthetic agent widely used in veterinary medicine for the induction and maintenance of general anesthesia. It is particularly valuable for outpatient diagnostics or minor procedures due to its rapid onset and smooth, rapid recovery profile. **Key Clinical Features:** * **Rapid Onset & Recovery:** Induces anesthesia within 30-60 seconds; recovery is typically smooth and rapid due to redistribution from the CNS to other tissues. * **Organ Function:** Safe for use in animals with mild to moderate cardiac disease, as well as liver or renal disease. * **Extra-label Uses:** Frequently utilized as a continuous rate infusion (CRI) for refractory status epilepticus, especially in cases of hepatic encephalopathy where pentobarbital may be contraindicated. * **Feline Considerations:** Cats lack the robust glucuronidation pathways present in dogs, making them susceptible to prolonged recoveries, Heinz body anemia, and malaise with repeated daily use or prolonged infusions. > **Clinical Pearl:** Propofol provides **no analgesia**. Appropriate perioperative analgesic protocols (e.g., opioids, NSAIDs, local blocks) must be employed for painful procedures.
Mecanismo: 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.
Dosificación por especie
- 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
Vías de administración
Contraindicaciones
- 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)
Efectos adversos
- 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
Interacciones farmacológicas
- 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%.
Monitorización
- 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
Sobredosis
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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