DOSAGE & ADMINISTRATION
Premedication
Premedication shouldbe selected according to the need of the individual patient, taking intoaccount that secretions are weakly stimulated by isoflurane, and the heart ratetends to be increased. The use of anticholinergic drugs is a matter of choice.
InspiredConcentration
The concentration ofisoflurane being delivered from a vaporizer during anesthesia should be known.
This may beaccomplished by using:
a) vaporizerscalibrated specifically for isoflurane;
b) vaporizers fromwhich delivered flows can be calculated, such as vaporizers delivering asaturated vapor which is then diluted. The delivered concentration from such avaporizer may be calculated using the formula:
% Isoflurane = 100 PVFV
FT (PA– PV)
where:
PA =Pressure of atmosphere
PV = Vaporpressure of isoflurane
FV = Flowof gas through vaporizer (mL/min)
FT = Totalgas flow (mL/min)
Isoflurane containsno stabilizer. Nothing in the agent alters calibration or operation of these vaporizers.
Induction
Induction withisoflurane in oxygen or in combination with oxygen-nitrous oxide mixtures mayproduce coughing, breath holding, or laryngospasm. These difficulties may beavoided by the use of a hypnotic dose of an ultra-short-acting barbiturate.Inspired concentrations of 1.5 to 3.0% isoflurane usually produce surgicalanesthesia in 7 to 10 minutes.
Maintenance
Surgical levels ofanesthesia may be sustained with a 1.0 to 2.5% concentration when nitrous oxideis used concomitantly. An additional 0.5 to 1.0% may be required whenisoflurane is given using oxygen alone. If added relaxation is required,supplemental doses of muscle relaxants may be used.
The level of blood pressure during maintenance is an inverse function ofisoflurane concentration in the absence of other complicating problems.Excessive decreases may be due to depth of anesthesia and in such instances maybe corrected by lightening anesthesia.
|