What is the explanation for this occurrence of orthostatic hypotension after sympathectomy in a patient?

A suppressed response of the baroreceptor mechanism -orthostatic hypotension is a decrease in arterial pressure that occurs when a person moves from a supine to a standing position. a person with a normal baroreceptor mechanism responds to a decrease in arterial pressure through the vasomotor center by increasing sympathetic outflow and decreasing parasympathetic outflow. the sympathetic component helps to restore blood pressure by increasing heart rate, contractility, total peripheral resistance (tpr), and mean systemic pressure. in a patient who has undergone a sympathectomy, the sympathetic component of the baroreceptor mechanism is absent