Sevoflurane

Inhalation Anesthetic Halogenated Ether

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog Inhalation (via mask or endotracheal tube) Induction: 3-5% (vaporizer setting) for mask induction; Maintenance: 1.5-2.5% Continuous administration Duration: As needed for procedure
Notes: Use with appropriate carrier gas (oxygen). Monitor depth of anesthesia and vital signs.
Cat Inhalation (via mask or endotracheal tube) Induction: 4-6% (vaporizer setting) for mask induction; Maintenance: 2-3% Continuous administration Duration: As needed for procedure
Notes: Cats may require higher concentrations for induction due to airway resistance.
Horse Inhalation (via endotracheal tube) Maintenance: 2-4% (vaporizer setting) after induction with IV agents Continuous administration Duration: As needed for procedure
Notes: Often used with oxygen and mechanical ventilation. Monitor blood pressure and depth.
Cattle Inhalation (via endotracheal tube) Maintenance: 2-3% (vaporizer setting) after induction with IV agents Continuous administration Duration: As needed for procedure
Notes: May be used in field anesthesia with portable vaporizers. Ensure adequate ventilation.
Small Ruminants (Sheep, Goats) Inhalation (via mask or endotracheal tube) Induction: 4-5% (mask); Maintenance: 2-3% Continuous administration Duration: As needed for procedure
Notes: Ruminants are prone to regurgitation; consider fasting and intubation with cuffed tube.
Rabbit Inhalation (via mask or endotracheal tube) Induction: 4-5% (mask); Maintenance: 2-3% Continuous administration Duration: As needed for procedure
Notes: Rabbits are difficult to intubate; mask induction is common. Monitor respiratory rate closely.
Bird (Poultry, Pet Birds) Inhalation (via mask or endotracheal tube) Induction: 3-5% (mask); Maintenance: 2-3% Continuous administration Duration: As needed for procedure
Notes: Birds have high metabolic rates; use precision vaporizer. Avoid overdose due to rapid uptake.
Exotic (Reptiles, Small Mammals) Inhalation (via mask or chamber) Induction: 3-5% (chamber or mask); Maintenance: 1-3% Continuous administration Duration: As needed for procedure
Notes: Reptiles may require lower concentrations due to slower metabolism. Monitor heart rate and respiration.

Clinical Indications & Species Uses

General Indications
  • General anesthesia for surgical procedures
  • Anesthetic maintenance in various species
Dog (Canine)
  • Induction and maintenance of general anesthesia
  • Anesthetic maintenance during surgical procedures
Cat (Feline)
  • Induction and maintenance of general anesthesia
  • Anesthetic maintenance during surgical procedures
Horse (Equine)
  • Maintenance of general anesthesia
  • Induction (with co-induction agents)
Cattle (Bovine)
  • Maintenance of general anesthesia (often used in calves and adult cattle for field anesthesia)
Small Ruminants (Sheep / Goat)
  • Maintenance of general anesthesia in sheep and goats
Rabbit & Small Mammals
  • Induction and maintenance of general anesthesia
Avian & Poultry
  • Maintenance of general anesthesia in birds (mask induction possible)
Exotic & Other Species
  • Maintenance of anesthesia in reptiles, small mammals (ferrets, guinea pigs), and zoo animals

Pharmacology & Mechanism of Action

Drug Class: Inhalation Anesthetic | Pharmacological Group: Halogenated Ether

Mechanism of Action: Sevoflurane produces dose-dependent central nervous system depression by enhancing the activity of inhibitory GABA-A receptors and inhibiting excitatory NMDA receptors, leading to immobility, amnesia, and unconsciousness. It also potentiates glycine receptors and modulates other ion channels, contributing to its anesthetic effects.

Pharmacodynamics: Sevoflurane has a low blood:gas partition coefficient (0.65), resulting in rapid induction and recovery from anesthesia. It provides dose-dependent decreases in blood pressure, systemic vascular resistance, and cardiac output, with minimal effect on heart rate. It also causes dose-dependent respiratory depression and bronchodilation. It has a pungency that is low, making it suitable for mask induction.

⚑ Pharmacokinetics Summary

Absorption: Inhalation: Rapidly absorbed through the alveoli into the bloodstream. The rate of uptake is influenced by alveolar ventilation, cardiac output, and the blood:gas partition coefficient.
Distribution: Widely distributed to highly perfused tissues (brain, heart, liver, kidneys) initially, then to muscle and fat. Crosses the blood-brain barrier and placenta.
Metabolism: Metabolized in the liver by cytochrome P450 (CYP2E1) to hexafluoroisopropanol (HFIP) and inorganic fluoride. The extent of metabolism is approximately 5% in humans, but may be slightly higher in some animal species.
Excretion: Primarily eliminated unchanged via the lungs (exhaled). The metabolites are conjugated with glucuronic acid and excreted in urine. Inorganic fluoride is excreted renally.
Half-Life: Context-sensitive half-life: approximately 2-5 minutes in dogs and cats after discontinuation, depending on duration of anesthesia.
Bioavailability: Not applicable (inhalational agent); pulmonary uptake is near 100% of delivered dose.
Protein Binding: Minimal (less than 5%)

Available Formulations & Strengths

Inhalation Liquid (for vaporization) 100% sevoflurane (250 mL bottle) (Inhalation)

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to sevoflurane or other halogenated anesthetics
  • History of malignant hyperthermia (in susceptible species, e.g., pigs, dogs, cats)
  • Severe hepatic or renal disease (use with caution; may exacerbate dysfunction)
  • Patients with increased intracranial pressure (unless appropriately managed)
  • Patients with known or suspected genetic susceptibility to malignant hyperthermia
Warnings & Clinical Precautions:
  • Use with caution in patients with cardiovascular disease, hypotension, or hypovolemia
  • Monitor depth of anesthesia and vital signs (heart rate, respiratory rate, blood pressure, oxygen saturation)
  • Sevoflurane can cause dose-dependent respiratory depression; be prepared to assist ventilation
  • In horses, sevoflurane may cause hypotension; monitor and support blood pressure
  • Use precision vaporizers to avoid accidental overdose
  • Avoid exposure of personnel to waste anesthetic gases; use scavenging systems
  • In food animals, observe withdrawal times
  • May cause transient hyperkalemia in some species (rare)
  • Use with caution in patients with renal impairment; monitor fluoride levels if prolonged anesthesia

Adverse Effects & Reactions

Common:

  • Hypotension
  • Respiratory depression
  • Hypothermia
  • Recovery excitement (especially in horses)
  • Nausea and vomiting (in dogs and cats during recovery)

Serious / Severe:

  • Malignant hyperthermia (rare but potentially fatal)
  • Cardiac arrhythmias
  • Hepatic necrosis (rare)
  • Renal toxicity (due to fluoride, especially with prolonged use)
  • Seizures (rare, during induction or recovery)

Rare:

  • Hyperkalemia
  • Metabolic acidosis
  • Anaphylactoid reactions
  • Carbon monoxide production in soda lime (when desiccated)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Opioids (e.g., fentanyl, morphine) Additive respiratory depression and sedation; may reduce anesthetic requirements (MAC-sparing effect) Moderate
Benzodiazepines (e.g., diazepam, midazolam) Additive sedation and muscle relaxation; may reduce anesthetic requirements Mild
Alpha-2 agonists (e.g., xylazine, dexmedetomidine) Significant reduction in anesthetic requirements; additive cardiovascular depression (bradycardia, hypotension) High
Neuromuscular blocking agents (e.g., atracurium, vecuronium) Sevoflurane potentiates the effects of non-depolarizing neuromuscular blockers; dose reduction may be needed Moderate
Epinephrine Increased risk of cardiac arrhythmias when used concurrently Moderate
Soda lime (CO2 absorbent) When desiccated, sevoflurane can degrade to compound A (nephrotoxic) and carbon monoxide; use fresh absorbent and avoid drying High

Overdose & Toxicity Management

Signs of Toxicity:

  • Severe hypotension
  • Bradycardia or cardiac arrest
  • Respiratory depression or apnea
  • Deep anesthesia with loss of reflexes
  • Hypothermia
  • Cyanosis

Emergency Treatment Protocol: Immediately discontinue sevoflurane, provide 100% oxygen, and support ventilation. Administer intravenous fluids to support blood pressure. Use vasopressors (e.g., dopamine, norepinephrine) if hypotension persists. Monitor cardiac rhythm and treat arrhythmias as needed. Provide supportive care until recovery. In cases of malignant hyperthermia, administer dantrolene and initiate aggressive cooling.

Food Animal Withdrawal Times

πŸ₯© Meat: 0 daysπŸ₯› Milk: 0 daysπŸ₯š Eggs: 0 days

Sevoflurane is rapidly eliminated via exhalation; however, for food animals, a withdrawal time of 24 hours is often recommended to ensure complete elimination and safety. Check local regulations.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature (20-25Β°C, 68-77Β°F)

Handling & Special Conditions: Keep container tightly closed. Do not use if the desiccant has changed color. Avoid exposure to extreme heat or open flames.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in dogs and cats (FDA). Not approved for food animals in the US, but may be used extra-label under veterinary supervision.

Extra-Label (Off-Label) Use: In the US, sevoflurane is FDA-approved for use in dogs and cats. Use in other species is considered extra-label and must comply with AMDUCA regulations. For food animals, a withdrawal time must be established and observed.

Clinical Pearls & Practice Notes

πŸ’‘ Clinical Insights: Sevoflurane is a valuable inhalant anesthetic in veterinary practice due to its rapid induction and recovery, making it ideal for short procedures and for patients with compromised cardiac function. It is less pungent than isoflurane, allowing smoother mask inductions. However, its cost is higher than isoflurane. It is important to use a precision vaporizer and to monitor anesthetic depth and vital signs closely. In horses, sevoflurane may cause more pronounced hypotension compared to isoflurane, so blood pressure support is often needed. For small mammals and birds, sevoflurane is often preferred due to its rapid onset and recovery. Always consider the individual patient's health status and use appropriate anesthetic protocols.

References & Literature

  • πŸ“š Plumb's Veterinary Drug Handbook
  • πŸ“š Papich Veterinary Pharmacology and Therapeutics
  • πŸ“š Compendium of Veterinary Products (CVP)