Dynamic cardiocirculatory control during propofol anesthesia in mechanically ventilated patients

We evaluated dynamic cardiovascular control by spectral analytical methods in 20 young adults anesthetized with propofol (2.5 mg/kg, followed by conti nuous infusion of 0.1 mg/kg/min) and in an awake control group during cycli c stimulation of the carotid baroreceptors via sinusoidal neck suction at 0 .2 Hz (baroreflex response mediated mainly by vagal activity) and at 0.1 Hz (baroreflex response mediated by vagal and sympathetic activity). During a nesthesia and mechanical ventilation at 0.25 Hz, major underdampened hemody namic oscillations occurred at 0.055 +/- 0.012 Hz. The response of RR inter vals to baroreceptor stimulation at 0.2 Hz was markedly decreased during an esthesia (median of transfer function magnitude between neck suction and RR intervals 3% of the awake control). Blood pressure response to barorecepto r stimulation at 0.1 Hz was significantly decreased during anesthesia to 26 % (systolic blood pressure), and 44% (diastolic blood pressure) of the awak e control. There was a significant delay in baroreflex effector responses d uring anesthesia. Our results demonstrate a markedly depressed vagally medi ated heart rate response and an impaired blood pressure response to cyclic baroreceptor stimulation during propofol anesthesia in mechanically ventila ted patients. The disturbed baroreflex control is accompanied by an irregul ar dynamic behavior of cardiovascular regulation, indicating a decreased st ability of the control system.