Halothane

It is not a potent analgesic & induction of anaesthesia with safe concentrations of halothane is delayed, and may last 10 mins. For this reason, a high concentration (3% or more) is commonly employed for the induction of anesthesia. Respiration is depressed by all anaesthetic concentrations of halothane. It obtunds laryngeal and pharyngeal reflexes to a marked degree, relaxes the masseter muscles, & inhibits salivation; this combination of effects renders tracheal intubation relatively simple. Laryngospasm, bronchospasm, and coughing are all inhibited.

Indications

Inhalation anaesthesia. It causes vasodilation even in the presence of shock. It is useful in providing a ‘blood less’ field for plastic operations, when employed as an agent capable of inducing deliberate hypotension.

Dosage

Induction : Upto 5% in air, oxygen or oxygen/nitrous oxide. Maint : 0.5-1%.

Special Precautions

Induction of anaesthesia may be delayed and recovery is necessarily prolonged. In neurosurgery use with moderate hyperventilation Adrenaline to be used with caution. Sensitizes the conducting tissues of the heart to the arrhythmogenic actions of catecholamines. In obstetrics to be used in lightest plane.

Side Effects

Shivering during recovery. Liver disease.

Drug Interactions

Neuromuscular blocking drugs are potentiated. Adrenaline/noradrenaline, chronic tricyclic antidepressants induced ventricular arrhythmias. Chlorpromazine enhances depressant effects.