Halosin

Halothane is a volatile anaesthetic which is suitable for the induction and maintenance of anaesthesia for all types of surgery and in patients of all ages.

When inhaled, Halothane is absorbed through the alveoli into the bloodstream. In the bloodstream, Halothane circulates through the body to the principal site of action, the brain. Here Halothane causes a progressive depression of the central nervous system, beginning with the higher centers (cerebral cortex) and spreading to the vital centers in the medulla. This depression is reversible. However, its mode of action, like all anaesthetic agents, is unknown.

Halothane has a relatively low solubility in blood and therefore alveoli/blood concentrations equilibrate rapidly. The triexponential decline in Halothane blood concentrations following the end of administration is thought to represent distribution into three compartments; the vessel rich group (brain/heart/liver), the musculature and adipose tissue. Approximately 80% of the inhaled Halothane is eliminated unchanged by the lungs. The remaining 20% is metabolized in the liver by oxidative and under hypoxic conditions, reductive pathways. The main metabolites are trifluoroacetic acid, bromide and chloride salts (via the oxidative pathway) and fluoride salts (via the reductive pathway). The concentrations of metabolites peak 24 hours post-operatively and are eliminated by renal excretion during the following week.

Increased risk of ventricular dysrhythmias with epinephrine. Increased risk of malignant hyperthermia with suxamethonium. Prolonged recovery from anaesth with concurrent use of ketamine for induction. May potentiate response to non-depolarising muscle relaxants, hypotensive agents (e.g. hexamethonium bromide, trimetaphan camsilate).

Post-op nausea, vomiting, and shivering; resp depression, hypotension, skeletal muscle relaxation, bradycardia.

Category C: Although the data from experimental investigations in animals cannot be directly related to man, it would be prudent to avoid general anaesthesia with inhalation agents during early pregnancy, except where such use is essential.

Lactation: There are no well controlled studies with Halothane in lactating women. Halothane has been detected in breast milk of lactating women, but the effect of Halothane on breast feed neonates has not been established. However, Halothane has been in wide use for over 30 years without apparent ill consequence

Caution should be exercised during administration of adrenaline to patients anaesthetised with Halothane as dysrhythmias may be precipitated. For this reason the dose of adrenaline should be restricted and beta-receptor antagonists administered if necessary. Ensure adequate room ventilation when Halothane is being used. Keep the concentration of Halothane in air as low as possible.

Effect on ability to drive or operate machinery: Patients should be advised that performance at skilled tasks, such as driving and operating machinery, may be impaired for some time after general anaesthesia.

Accidental ingestion: Cases of ingestion must be treated symptomatically.

General (Inhalation) anesthetics

Bottles of Halothane must be securely closed and stored in a cool dry place, protected from light. Halothane must be kept in the original container until immediately prior to its use.

Whilst in the liquid phase, Halothane must not be diluted or contaminated; however, in the vapour phase it may be administered together with Oxygen or a mixture of Nitrous Oxide and Oxygen.