Forane

Indications

Isoflurane is a general anaesthetic gas. It is breathed in to keep a patient unconscious and free of pain during surgery, after anaesthesia has been started, usually with an injection. It is used in adults and children in operating theatres.

How It Works

Isoflurane is a volatile liquid that turns into vapour in a special machine called a vaporiser. When it is breathed in, it passes from the lungs into the blood and then to the brain, where it calms nerve activity and causes deep unconsciousness. It also relaxes muscles to some degree. When the gas is stopped, it is breathed out and the patient wakes up fairly quickly.

Dosage and Administration

Isoflurane is given only by an anaesthetist (a doctor trained in anaesthesia) using a calibrated vaporiser and anaesthetic machine, usually mixed with oxygen, with or without nitrous oxide or air. The strength is adjusted continuously according to the patient's age, condition and response. Breathing, heart rate, blood pressure and oxygen levels are monitored throughout.

Interactions

Opioid pain killers (such as Fentanyl or Morphine), benzodiazepines (such as Midazolam) and nitrous oxide reduce the amount of Isoflurane needed. It strengthens the effect of muscle relaxants such as Atracurium or Vecuronium. Beta blockers and calcium channel blockers may add to the fall in blood pressure. Adrenaline may cause irregular heart rhythm. Tell the doctor about all medicines, including herbal products, before surgery.

Contraindications

• Known or suspected malignant hyperthermia (a rare, inherited, life threatening reaction to anaesthetic gases) in the patient or family.
• Previous liver problems or unexplained fever after an anaesthetic gas.
• Allergy to Isoflurane or other halogenated anaesthetics.
• Situations where general anaesthesia is unsuitable, as judged by the anaesthetist.

Side Effects

During anaesthesia it commonly lowers blood pressure and slows breathing; these are watched and treated by the team. On waking, people may have nausea, vomiting, shivering, sore throat, cough, drowsiness or brief confusion, especially older people. Children may be agitated when waking.

Get urgent medical help (the hospital team will act straight away) if there is very high temperature with stiff muscles, a fast heartbeat, breathing difficulty, or later yellowing of the skin or eyes, dark urine or severe tiredness after surgery.

Pregnancy and Lactation

Isoflurane is used in pregnancy only when surgery is needed and the anaesthetist judges it appropriate. High doses can relax the womb and increase bleeding during caesarean section. Very little reaches breast milk after the gas is stopped; breastfeeding can usually restart once the mother is awake and alert, as advised by the team.

Precautions and Warnings

Tell the doctor about any past reaction to anaesthesia, muscle disease, heart disease, raised pressure in the head, liver or kidney disease. Do not drive, use machines, drink alcohol or make important decisions for at least 24 hours after an anaesthetic. Repeated exposure in young children and pregnant women for long or many operations is weighed carefully by doctors.

Overdose

Too much can cause very low blood pressure and slowed breathing. The anaesthetist stops the gas, gives pure oxygen and supports breathing and circulation.

Therapeutic Class

General anaesthetic; volatile inhalational (halogenated ether) anaesthetic.

Storage

Hospital product: store as directed on the pack, usually below 30°C in a tightly closed bottle, away from light and heat.