Cardiac dysrhythmias, carbon dioxide tensions and blood halothane concentrations during dental anaesthesia.

Ninety-eight in-patients received halothane anaesthesia for dental surgery following intramuscular premedication with papavaretum and hyoscine. All anaesthetics involved tracheal intubation. Fifty patients breathed spontaneously and 48 were artifically ventilated. The incidence of ectopic dysrhythmias during surgery, both ventricular and supraventricular, was significantly higher in the spontaneously breathing group (34.0%) than in the artificially ventilated group (2.1%). Blood halothane concentrations and end-expiratory carbon dioxide tensions during surgery were both significantly higher in the spontaneously breathing group. However, regression analysis of the data failed to identify either factor as solely responsible for the different incidence of cardiac dysrhythmias. It is likely that at least one further factor is involved.