Isoflurane is general inhalation anaesthetic for use in induction and maintenance.
For this indication, competent medicine agencies globally authorize below treatments:
0.5 - 3 %
From 0.5 To 3 % once every day
MAC values for isoflurane vary with age. The table below indicates average MAC values for different age groups.
|AGE||Average MAC value|
|In 100% Oxygen||70% N2O|
|26 ± 4 years||1.28%||0.56%|
|44 ± 7 years||1.15%||0.50%|
|64 ± 5 years||1.05%||0.37%|
Premedication drugs should be selected according to the needs of the patient. The respiratory depressant effect of isoflurane should be taken into account. The use of anticholinergic drugs is a matter of choice, but may we advisable for inhalation induction in paediatrics.
As isoflurane has a mild pungency, inhalation should usually be preceded by the use of a short acting barbiturate, or other intravenous induction agent, to prevent coughing. Alternatively, isoflurane with oxygen or with an oxygen/nitrous oxide mixture may be administered.
It is recommended that induction with isoflurane be initiated at a concentration of 0.5%. Concentrations of 1.5-3.0% usually produce surgical anaesthesia in 7-10 minutes.
Adequate anaesthesia for surgery may be sustained with an inspired isoflurane concentration of 1.0% to 2.5% in an oxygen/nitrous oxide mixture. Additional isoflurane (0.5% to 1.0%) may be required when isoflurane is given with oxygen alone.
For caesarean section, 0.5-0.75% isoflurane in a mixture of oxygen/nitrous oxide is suitable to maintain anaesthesia for this procedure.
Arterial pressure levels during maintenance tend to be inversely related to alveolar isoflurane concentration in the absence of other complicating factors. Provided there are no other complicating factors this is probably due to peripheral vasodilation. Excessive falls in blood pressure may be due to the depth of anaesthesia and, in such circumstances, can be corrected by reducing the inspired isoflurane concentration.
Vaporisers specially calibrated for isoflurane should be used so that the concentration of anaesthetic can be accurately controlled.