In this study, baroreflex control of HR was completely inhibited in 9 of 21 patients in the depressor test but in only 1 of 19 patients in the pressor test. All patients who showed complete inhibition had received bilateral T2-3 sympathectomy. Responses to decreased blood pressure are mediated by the sympathetic nervous system, whereas responses to increased blood pressure predominantly involve vagal compensation (13). Therefore, it seems that the effects of sympathetic denervation were most prominent in the depressor test after ETS.
The suppression of baroreflex function can be detrimental during anesthetic management. In particular, a poorly preserved baroreflex response to decreasing blood pressure may exaggerate hemodynamic perturbation after a sudden loss of circulating blood volume. In addition, it is possible that patients who have received ETS will show unexpected HR responses after the administration of a vasopressor or vasodilator. We conclude that baroreflex response as a compensatory function for hemodynamic changes is suppressed in patients who receive ETS.Anesth Analg 2004;98:37-39
http://www.anesthesia-analgesia.org/cgi/content/full/98/1/37