Its poor analgesic properties necessitate deep planes of anaesthesia before surgery can be tolerated. For this reason it is generally not suitable as a sole agent without an analgesic supplement, eg nitrous oxide, trichloroethylene, local anaesthetic block or other analgesic, especially during spontaneous respiration. The depression of the cardiovascular system may cause bradycardia, hypotension and a reduction in cardiac output. These effects may be marked in children who should receive atropine either as premedication or i.v. The combined depressant effects on the circulation and respiration mean that during anaesthesia and the early recovery phase supplemental oxygen should always be given.
Halothane sensitises the heart to adrenaline and predisposes the patient to developing arrhythmias.
These arrhythmias occur most commonly in patients who are retaining CO 2 or who have an inadequate analgesic component in their anaesthetic. Injection of adrenaline by the surgeon during anaesthesia with halothane may be dangerous and the doses need to be carefully monitored. Postoperative shivering may occur which is usually shortlived. In common with all agents being considered in this article halothane causes an increase in intracranial blood flow and therefore pressure. Inhalation induction especially in upper airway problems such as partial obstruction.