Caution: Operating rooms should be provided with adequate ventilation to prevent the accumulation of anesthetic vapors.
Premedication: A premedication regimen, which may be employed depending upon the patient status, to avert excitement during induction, might include an anticholinergic, a tranquilizer, a muscle relaxant, and a short-acting barbiturate.
Inspired Concentration: The delivered concentration of isoflurane, USP should be known. Isoflurane may be vaporized using a flow-through vaporizer specifically calibrated for isoflurane. Vaporizers delivering a saturated vapor which then is diluted (e.g., Verni-trol® vaporizer) also may be used. The delivered concentration from such a vaporizer may be calculated using the formula:
% isoflurane
=
100PVFV
FT (PA-PV)
where:
PA
=
Pressure of atmosphere
PV
=
Vapor pressure of isoflurane
FV
=
Flow of gas through vaporizer (mL/min)
FT
=
Total gas flow used (mL/min)
Isoflurane contains no stabilizer. Nothing in the drug product alters calibration or operation of these vaporizers.
Induction:
Horses: Inspired concentrations of 3.0 to 5.0% isoflurane alone with oxygen following a barbiturate anesthetic induction are usually employed to induce surgical anesthesia in the horse.
Dogs: Inspired concentrations of 2.0 to 2.5% isoflurane alone with oxygen following a barbiturate anesthetic induction are usually employed to induce surgical anesthesia in the dog.
These concentrations con be expected to produce surgical anesthesia in 5 to 10 minutes.
Maintenance: The concentration of vapor necessary to maintain anesthesia is much less than that required to induce it.
Horses: Surgical levels of anesthesia in the horse may be sustained with a 1.5 to 1.8% concentration of isoflurane in oxygen.
Dogs: Surgical levels of anesthesia in the dog may be sustained with a 1.5 to 1.8% concentration of isoflurane in oxygen.
The level of blood pressure during maintenance is an inverse function of isoflurane concentration in the absence of other complicating problems. Excessive decreases, unless related to hypovolemia, may be due to depth of anesthesia and in such instances may be corrected by lightening the level of anesthesia.
Recovery from isoflurane anesthesia is typically uneventful.2