Source: FDA, National Drug Code (US) Revision Year: 2022
Isoflurane may be used for induction and maintenance of general anesthesia. Adequate data have not been developed to establish its application in obstetrical anesthesia.
Isoflurane should be administered only by persons trained in the administration of general anesthesia.
Facilities for maintenance of a patent airway, artificial ventilation, oxygen enrichment, and circulatory resuscitation must be immediately available.
Isoflurane is administered by inhalation. Isoflurane should be delivered from a vaporizer specifically designed for use with isoflurane.
The minimum alveolar concentration (MAC) of isoflurane decreases with increasing patient age.
Dosage for induction and maintenance must be individualized and titrated to the desired effect according to the patient’s age and clinical status.
Premedication should be selected according to the need of the individual patient, taking into account that secretions are weakly stimulated by isoflurane, and the heart rate tends to be increased. The use of anticholinergic drugs is a matter of choice.
Induction with isoflurane in oxygen or in combination with oxygen-nitrous oxide mixtures may produce coughing, breath holding, or laryngospasm and bronchospasm, which increases with the concentration of isoflurane. These difficulties may be avoided by the use of a hypnotic dose of an ultra-short-acting barbiturate. Inspired concentrations of 1.5 to 3.0% isoflurane usually produce surgical anesthesia in 7 to 10 minutes.
Isoflurane MAC values according to age are shown below:
| Age | Average MAC Value In 100% Oxygen | Average MAC Value In 30% Oxygen and 70% N2O |
|---|---|---|
| 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% | |
| 6-10 years | 1.45% | |
| 11-18 years | 1.38% | |
| 19-30 years | 1.28% | 0.56% |
| 31-55 years | 1.15% | 0.50% |
| 55-83 years | 1.05% | 0.37% |
Dosage for induction and maintenance must be individualized and titrated to the desired effect according to the patient’s age and clinical status.
Surgical levels of anesthesia may be sustained with a 1.0 to 2.5% concentration when nitrous oxide is used concomitantly. An additional 0.5 to 1.0% may be required when isoflurane 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 of isoflurane concentration in the absence of other complicating problems. Excessive decreases may be due to depth of anesthesia and in such instances may be corrected by lightening anesthesia.
In the event of overdosage, or what may appear to be overdosage, the following action should be taken, as appropriate:
Stop drug administration, establish a clear airway, and initiate assisted or controlled ventilation with pure oxygen. Monitor cardiovascular function and manage signs of poor end-organ perfusion as clinically indicated.
OCCUPATIONAL CAUTION
There is no specific work exposure limit established for Isoflurane. However, the National Institute for Occupational Safety and Health Administration (NIOSH) recommends that no worker should be exposed at ceiling concentrations greater than 2 ppm of any halogenated anesthetic agent over a sampling period not to exceed one hour.
The predicted effects of acute overexposure by inhalation of Isoflurane include headache, dizziness or (in extreme cases) unconsciousness. There are no documented adverse effects of chronic exposure to halogenated anesthetic vapors (Waste Anesthetic Gases or WAGs) in the workplace. Although results of some epidemiological studies suggest a link between exposure to halogenated anesthetics and increased health problems (particularly spontaneous abortion), the relationship is not conclusive. Since exposure to WAGs is one possible factor in the findings for these studies, operating room personnel, and pregnant women in particular, should minimize exposure. Precautions include adequate general ventilation in the operating room, the use of a well-designed and well-maintained scavenging system, work practices to minimize leaks and spills while the anesthetic agent is in use, and routine equipment maintenance to minimize leaks. (See PRECAUTIONS).
Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature]. Preserve in tight containers. Isoflurane contains no additives and has been demonstrated to be stable at room temperature for a period of up to five years.
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