Halothane
Mechanism :
Halothane is an inhalation anesthetic. Induction and recovery are rapid, and depth of anesthesia can be rapidly altered. Halothane progressively depresses respiration. There may be tachypnea with reduced tidal volume and alveolar ventilation. It is not an irritant to the respiratory tract, and no increase in salivary or bronchial secretions ordinarily occurs. Pharyngeal and laryngeal reflexes are rapidly obtunded. It causes bronchodilation. Hypoxia, acidosis, or apnea may develop during deep anesthesia.
Indication :
- Induction and maintenance of general anaesthesia.
Contraindications :
Not recommended for obstetrical anesthesia except when uterine relaxation is required.
Dosing :
The induction dose varies but is usually ranges from 0.5% to 3% while the maintenance dose ranges from 0.5% to 1.5%.
Adverse Effect :
Muscle rigidity, hypercapnia, tachycardia, ventricular arrhythmias, cyanosis, tachypnea, unstable blood pressure, malignant hyperthermia, post-operative nausea and vomiting, mild hepatotoxicity, massive centrilobular necrosis leading to fulminant liver failure.
Interaction :
Non-Depolarising Muscle Relaxants: Augments the action of non-depolarising muscle relaxants and the muscle relaxant effects of aminoglycosides.
Tubocurarine: May augment the hypotension caused by the ganglionic-blocking effect of tubocurarine.
Adrenaline: Caution should be exercised during the administration of adrenaline to patients anaesthetised with halothane as arrhythmias may be precipitated. Caution should also be applied for other sympathomimetics, and for aminophylline and theophylline and tricyclic antidepressants, which may also precipitate arrhythmias.
Hepatic Dose :
Avoid in hepatic impairment.