ATROPINE ABOLISHES ELECTROENCEPHALOGRAM-ASSOCIATED HEART-RATE CHANGESWITHOUT AN EFFECT ON RESPIRATORY SINUS ARRHYTHMIA DURING ANESTHESIA IN HUMANS

Heart rate fluctuates with the electroencephalogram burst suppression pattern during anaesthesia: increasing at burst onset and decreasing a t suppression. Heart rate also oscillates with positive pressure venti lation. The effects of atropine on these heart rate changes were studi ed in 12 patients during isoflurane anaesthesia and positive pressure ventilation at a frequency of 6 cycles min(-1). Four additional patien ts served as controls. A bolus dose of atropine (20 mu g kg(-1) intrav enously) abolished the electroencephalogram-correlated heart rate chan ges; however, the amplitude of respiratory sinus arrhythmia was not ch anged after atropine. The control mechanism of the burst suppression p attern in electroencephalogram also affects parasympathetic heart rate control. The control mechanisms of respiratory sinus arrhythmia durin g anaesthesia with positive pressure ventilation differ from those dur ing spontaneous breathing awake.