Posology : מינונים

4.2      Posology and method of administration
In order to be able to accurately control the precise concentration of isoflurane, vaporisers that have been specially calibrated for isoflurane should be used.

Induction of anaesthesia:
If isoflurane is used for induction of anaesthesia, a starting concentration of 0.5% is recommended. Concentrations of 1.3-3.0% usually bring about surgical anaesthesia within 7 to 10 minutes.

It is recommended that use be made of a hypnotic dose of a short acting barbiturate oranother product such as propofol, etomidate, or midazolam in order to avoid coughing or laryngospasm, which can arise if induction is carried out with Isoflurane alone or in combination with oxygen or with an oxygen-nitrous oxide mixture.

Maintenance of anaesthesia:
Anaesthesia can be maintained during surgery using a concentration of 1.0-2.5% with the simultaneous administration of N2O and O2.

A higher concentration of 1.5-3.5% of Isoflurane is necessary if Isoflurane is administered with pure oxygen.

Recovery:
The concentration of Isoflurane must be reduced to 0.5% at the end of the operation, orto 0% during closure of the wound to allow prompt recovery.

If all administration of anaesthetic agents has been stopped, the air passages of thepatient should be ventilated several times with 100% oxygen until complete awakening occurs.
If the vector gas is a mixture of 50% O2 and 50% N2O, the value of the minimum alveolar concentration of isoflurane is approximately 0.65%.



ADULTS
Age                               Average MAC Value In 100%              70% N2O Oxygen
26 ± 4 years                                     1.28%                     0.56%
44 ± 7 years                                     1.15%                     0.50%
64 ± 5 years                                     1.05%                     0.37%             PAEDIATRIC POPULATION
Age                               Average MAC Value In 100%
Oxygen
Preterm neonates     < 32 weeks gestational age                            1.28%
Preterm neonates 32-37 weeks gestational age                            1.41%
0-1 month                                        1.60%
1-6 months                                       1.87%
6-12 months                                      1.80%
1-5 years                                        1.60%


Premedication
Drugs used for premedication should be selected for the individual patient bearing in mind the respiratory depressant effect of isoflurane. The use of anticholinergic drugs is a matter of choice, but may be advisable for inhalation induction in paediatrics.

Induction of anaesthesia in children:
Isoflurane is not recommended for use as an inhalation induction agent in infants and children because of the occurrence of cough, breath-holding, desaturation, increased secretions and laryngospasm (see section 4.4).

Elderly
As with other agents, lesser concentrations of isoflurane are normally required to maintain surgical anaesthesia in elderly patients. See above for MAC values related to age.