SEVOFLO- sevoflurane inhalant
Inhalation Anesthetic For Use in Dogs
Caution: Federal law restricts this drug to use by or on the order of a licensed veterinarian.
SevoFlo (sevoflurane) is a volatile liquid, is a halogenated general inhalation anesthetic drug. Its chemical name is fluoromethyl 2,2,2-trifluoro-l-(trifluoromethyl) ethyl ether, and its structural formula is:
Sevoflurane Physical Constants are:
|Boiling Point at 760 mm Hg||58.6°C|
|Specific Gravity at 20 °C||1.520 — 1.525 g/mL|
|Vapor Pressure in mm Hg||at 20 °C||157|
|Distribution Partition Coefficients||at 37°C:|
|Blood/Gas||0.63 — 0.69|
|Olive Oil/Gas||47 — 54|
|Mean Component/Gas Partition Coefficients at 25°C for Polymers Used Commonly in Medical Applications:|
Sevoflurane is nonflammable and nonexplosive as defined by the requirements of International Electrotechnical Commission 601-2-13.
Sevoflurane is a clear, colorless, stable liquid containing no additives or chemical stabilizers. Sevoflurane is nonpungent. It is miscible with ethanol, ether, chloroform and petroleum benzene, and it is slightly soluble in water. Sevoflurane is stable when stored under normal room lighting condition according to instructions.
SevoFlo is indicated for induction and maintenance of general anesthesia in dogs.
Inspired Concentration: The delivered concentration of SevoFlo should be known. Since the depth of anesthesia may be altered easily and rapidly, only vaporizers producing predictable percentage concentrations of sevoflurane should be used. Sevoflurane should be vaporized using a precision vaporizer specifically calibrated for sevoflurane. Sevoflurane contains no stabilizer. Nothing in the drug product alters calibration or operation of these vaporizers. The administration of general anesthesia must be individualized based on the patient’s response. WHEN USING SEVOFLURANE, PATIENTS SHOULD BE CONTINUOUSLY MONITORED AND FACILITIES FOR MAINTENANCE OF PATENT AIRWAY, ARTIFICIAL VENTILATION, AND OXYGEN SUPPLEMENTATION MUST BE IMMEDIATELY AVAILABLE.
Replacement of Desiccated CO2 Absorbents: When a clinician suspects that the CO2 absorbent may be desiccated, it should be replaced. An exothermic reaction occurs when sevoflurane is exposed to CO2 absorbents. This reaction is increased when the CO2 absorbent becomes desiccated (see PRECAUTIONS).
Premedication: No specific premedication is either indicated or contraindicated with sevoflurane. The necessity for and choice of premedication is left to the discretion of the veterinarian. Preanesthetic doses for premedicants may be lower than the label directions for their use as a single medication.1
Induction: For mask induction using sevoflurane alone, inspired concentrations of up to 7% sevoflurane with oxygen are employed to induce surgical anesthesia in the healthy dog. These concentrations can be expected to produce surgical anesthesia in 3 to 14 minutes. Due to the rapid and dose dependent changes in anesthetic depth, care should be taken to prevent overdosing. Respiration must be monitored closely in the dog and supported when necessary with supplemental oxygen and/or assisted ventilation.
Maintenance: SevoFlo may be used for maintenance anesthesia following mask induction using sevoflurane or following injectable induction agents. The concentration of vapor necessary to maintain anesthesia is much less than that required to induce it.
Surgical levels of anesthesia in the healthy dog may be maintained with inhaled concentrations of 3.7-4.0% sevoflurane in oxygen in the absence of premedication and 3.3-3.6% in the presence of premedication. The use of injectable induction agents without premedication has little effect on the concentrations of sevoflurane required for maintenance. Anesthetic regimens that include opioid, alpha2 — agonist, benzodiazepine or phenothiazine premedication will allow the use of lower sevoflurane maintenance concentrations.
SevoFlo is contraindicated in dogs with a known sensitivity to sevoflurane or other halogenated agents.
Sevoflurane is a profound respiratory depressant.
DUE TO THE RAPID AND DOSE DEPENDENT CHANGES IN ANESTHETIC DEPTH, RESPIRATION MUST BE MONITORED CLOSELY IN THE DOG AND SUPPORTED WHEN NECESSARY WITH SUPPLEMENTAL OXYGEN AND/OR ASSISTED VENTILATION.
In cases of severe cardiopulmonary depression, discontinue drug administration, ensure the existence of a patent airway and initiate assisted or controlled ventilation with pure oxygen. Cardiovascular depression should be treated with plasma expanders, pressor agents, antiarrhythmic agents or other techniques as appropriate for the observed abnormality.
Due to sevoflurane’s low solubility in blood, increasing the concentration may result in rapid changes in anesthetic depth and hemodynamic changes (dose dependent decreases in respiratory rate and blood pressure) compared to other volatile anesthetics. Excessive decreases in blood pressure or respiratory depression may be corrected by decreasing or discontinuing the inspired concentration of sevoflurane.
Potassium hydroxide containing CO2 absorbents (e.g. BARALYME®) are not recommended for use with sevoflurane.
The most frequently reported adverse reactions during maintenance anesthesia were hypotension, followed by tachypnea, muscle tenseness, excitation, apnea, muscle fasciculations and emesis.
Infrequent adverse reactions include paddling, retching, salivation, cyanosis, premature ventricular contractions and excessive cardiopulmonary depression.
Transient elevations in liver function tests and white blood cell count may occur with sevoflurane, as with the use of other halogenated anesthetic agents.
Halogenated volatile anesthetics can react with desiccated carbon dioxide (CO2 ) absorbents to produce carbon monoxide (CO) that may result in elevated carboxyhemoglobin levels in some patients. To prevent this reaction, sevoflurane should not be passed through desiccated soda lime or barium hydroxide lime.
Replacement of Desiccated CO2 Absorbents:
When a clinician suspects that the CO2 absorbent may be desiccated, it should be replaced before administration of sevoflurane. The exothermic reaction that occurs with sevoflurane and CO2 absorbents is increased when the CO2 absorbent becomes desiccated, such as after an extended period of dry gas flow through the CO2 absorbent canisters. Extremely rare cases of spontaneous fire in the respiratory circuit of the anesthesia machine have been reported during sevoflurane use in conjunction with the use of a desiccated CO2 absorbent, specifically those containing potassium hydroxide (e.g. BARALYME). Potassium hydroxide-containing CO2 absorbents are not recommended for use with sevoflurane. An unusually delayed rise in the inspired gas concentration (decreased delivery) of sevoflurane compared with the vaporizer setting may indicate excessive heating of the CO2 absorbent canister and chemical breakdown of sevoflurane. The color indicator of most CO2 absorbent may not change upon desiccation. Therefore, the lack of significant color change should not be taken as an assurance of adequate hydration. CO2 absorbents should be replaced routinely regardless of the state of the color indicator.
The use of some anesthetic regimens that include sevoflurane may result in bradycardia that is reversible with anticholinergics. Studies using sevoflurane anesthetic regimens that included atropine or glycopyrrolate as premedicants showed these anticholinergics to be compatible with sevoflurane in dogs.
During the induction and maintenance of anesthesia, increasing the concentration of sevoflurane produces dose dependent decreases in blood pressure and respiratory rate. Due to sevoflurane’s low solubility in blood, these changes may occur more rapidly than with other volatile anesthetics. Excessive decreases in blood pressure or respiratory depression may be related to depth of anesthesia and may be corrected by decreasing the inspired concentration of sevoflurane. RESPIRATION MUST BE MONITORED CLOSELY IN THE DOG AND SUPPORTED WHEN NECESSARY WITH SUPPLEMENTAL OXYGEN AND/OR ASSISTED VENTILATION. The low solubility of sevoflurane also facilitates rapid elimination by the lungs.
The use of sevoflurane in humans increases both the intensity and duration of neuromuscular blockade induced by nondepolarizing muscle relaxants. The use of sevoflurane with nondepolarizing muscle relaxants has not been evaluated in dogs.
Compromised or debilitated dogs: Doses may need adjustment for geriatric or debilitated dogs. Because clinical experience in administering sevoflurane to dogs with renal, hepatic and cardiovascular insufficiency is limited, its safety in these dogs has not been established.
Breeding dogs: The safety of sevoflurane in dogs used for breeding purposes, during pregnancy, or in lactating bitches, has not been evaluated.
Neonates: The safety of sevoflurane in young dogs (less than 12 weeks of age) has not been evaluated.
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