Isoflurane is indicated for the induction and maintenance of general anesthesia. However, sufficient evidence has not been established to support its use in obstetrical anesthesia.

Isoflurane is a non-flammable volatile liquid used as a general inhalation anesthetic. Both induction and recovery from Isoflurane anesthesia occur rapidly. It has a mild pungent odor, which may limit the speed of induction, but it does not significantly increase salivation or airway secretions. Reflexes of the pharynx and larynx are effectively suppressed. Isoflurane causes marked respiratory depression. As the anesthetic depth increases, tidal volume decreases while respiratory rate remains relatively unchanged. This respiratory depression may be partially reversed by surgical stimulation. Isoflurane may also produce occasional sighing respiration similar to that seen with other anesthetics, though less frequently. Blood pressure typically decreases during induction but tends to improve with surgical stimulation. Increasing depth of anesthesia results in further reduction of blood pressure. The use of nitrous oxide can reduce the required concentration of Isoflurane and may lessen the degree of hypotension. With controlled ventilation and normal carbon dioxide levels, cardiac output is generally maintained due to an increase in heart rate compensating for reduced stroke volume. During spontaneous breathing, increased carbon dioxide levels may further elevate heart rate and cardiac output. Isoflurane enhances the effects of all commonly used muscle relaxants, especially non-depolarizing agents. Neostigmine can reverse the effects of non-depolarizing muscle relaxants in the presence of Isoflurane. All commonly used muscle relaxants are compatible with Isoflurane.

Route of administration: It should be administered by inhalation delivered from a vaporizer specifically designed for use with isoflurane. Isoflurane should be administered only by persons trained in the administration of general anaesthesia. Facilities for maintenance of a patient airway, artificial ventilation, oxygen enrichment and circulatory resuscitation must be immediately available. The minimum alveolar concentration (MAC) of isoflurane decreases with increasing patient age.

Premedication: 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.

Induction: Induction with isoflurane in oxygen or in combination with oxygen-nitrous oxide mixtures may produce coughing, breath holding, 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 anaesthesia in 7 to 10 minutes.

Surgical levels of anaesthesia 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 anaesthesia and in such instances may be corrected by lightening anaesthesia.

Isoflurane interacts with several medications. Opioids such as fentanyl reduce the minimum alveolar concentration (MAC) of isoflurane and, when used together, may cause a synergistic decrease in blood pressure and respiratory rate. Nitrous oxide also lowers the MAC requirement of isoflurane. Isoflurane enhances the effects of all muscle relaxants, thereby reducing the required dose of neuromuscular blocking agents including succinylcholine, atracurium, pancuronium, rocuronium, and vecuronium. Patients receiving calcium channel blockers may experience significant hypotension when combined with isoflurane. Concomitant use of beta-blockers may intensify cardiovascular effects such as hypotension and reduced cardiac contractility. The combined use of MAO inhibitors and inhalational anesthetics may increase the risk of hemodynamic instability during surgical procedures.

Isoflurane is contraindicated in patients with known hypersensitivity to isoflurane, other halogenated anesthetics, or any component of the formulation. It should not be used in patients where general anesthesia is contraindicated, or in those with known or suspected susceptibility to malignant hyperthermia. It is also contraindicated in patients with a history of hepatitis or unexplained moderate to severe liver dysfunction following exposure to halogenated inhalational anesthetics.

Common adverse effects include delirium, agitation, breath-holding, cough, laryngospasm, nausea, vomiting, chills, shivering, and cardiac arrhythmias.

There are no well-controlled studies of isoflurane in pregnant women. Due to insufficient data regarding its excretion in human milk, careful consideration of risks and benefits is required before use in breastfeeding women.

Use of inhalational anesthetics has been associated with rare increases in serum potassium levels, potentially leading to cardiac arrhythmias or death in pediatric patients postoperatively. In susceptible individuals, isoflurane may trigger malignant hyperthermia, a serious condition requiring immediate discontinuation of the drug and treatment with intravenous dantrolene. Postoperative liver dysfunction, including hepatitis and, in rare cases, fatal liver failure, has been reported. QT interval prolongation and rare cases of torsade de pointes have also been observed; therefore, cardiac monitoring is recommended in at-risk patients. Continuous monitoring of respiration and cardiovascular status is essential. Assisted or controlled ventilation should be provided if necessary. Maintaining stable hemodynamics is important, particularly in patients with coronary artery disease. Extra caution is needed in patients who are hypovolemic, hypotensive, or otherwise hemodynamically unstable. In patients with increased intracranial pressure, isoflurane should be used alongside appropriate measures to reduce intracranial pressure. If CO₂ absorbent is suspected to be dried out, it should be replaced before use. Mild impairment in cognitive function may occur for a few days following anesthesia.

Pediatric Use: Repeated or prolonged exposure to anesthetic agents in children under 3 years of age may affect brain development. The risks and benefits should be carefully considered before elective procedures.

In case of overdose, discontinue isoflurane immediately, ensure airway patency, and provide assisted ventilation with 100% oxygen. Monitor cardiovascular function and manage accordingly.

General inhalational anesthetic

Store below 25°C in a dry place, protected from light. Keep out of reach of children.