Heart rate changes in halothane anaesthesia: effect of varying doses of atropine and neostigmine.

Heart rate changes during halothane-tubocurarine anaesthesia (Group I, 60 patients), and pethidine-tubocurarine (Group II, 20 patients) have been studied. Significant changes were noted immediately after thiopentone induction, after intubation and after atropine 1.2 mg, 1.8 mg, or 3.0 mg. It was found that atropine 1.8 mg was as effective as atropine 3.0 mg in increasing heart rate, Atropine caused a similar degree of tachycardia in patients who were given halothane 1.5-2.0 per cent or pethidine 100-150 mg in incremental doses of 25 mg in addition to the inspired mixture of nitrous oxide 6 l./min and oxygen 3 L/min. Neostigmine 5 mg significantly reduced the heart rate irrespective of the preceding dose of atropine.