Atropine abolishes electroencephalogram-associated heart rate changes without an effect on respiratory sinus arrhythmia during anaesthesia in humans

Heart rate fluctuates with the electroencephalogram burst suppression pattern during anaesthesia: increasing at burst onset and decreasing at suppression. Heart rate also oscillates with positive pressure ventilation. The effects of atropine on these heart rate changes were studied in 12 patients during isoflurane anaesthesia and positive pressure ventilation at a frequency of 6 cycles min^‐1. Four additional patients served as controls. A bolus dose of atropine (20µg kg^‐1 intravenously) abolished the electroencephalogram‐correlated heart rate changes; however, the amplitude of respiratory sinus arrhythmia was not changed after atropine. The control mechanism of the burst suppression pattern in electroencephalogram also affects parasympathetic heart rate control. The control mechanisms of respiratory sinus arrhythmia during anaesthesia with positive pressure ventilation differ from those during spontaneous breathing awake.