THIS IS part of an electroencephalogram (EEG) tracing (Figure 1) of a 65-year-old man undergoing EEG monitoring during carotid endarterectomy. During surgical exposure and manipulation, there was a sudden episode of hypotension and subsequent asystole (black arrow). After 3 to 4 seconds of asystole, there was diffuse electrographic slowing, followed by a severe generalized attenuation of cortical activity (sensitivity, 3 µV/mm). The patient remained asystolic for about 15 seconds. No resuscitative intervention was performed (eg, precordial thump). Surgical manipulation was stopped and the brain activity spontaneously recurred 5 seconds after the appearance of the cardiac rhythm (white arrow). Pressure or stretch of the carotid sinus gave rise to impulses carried by the sinus nerve of Hering to the medulla oblongata, producing a reflex hypotension, bradycardia, or even asystole. The solid vertical line on the left side of the tracing represents a change of the EEG sensitivity from 5 to 3 µV/mm.
Tan GL. Baroreflex Sensitivity. Arch Neurol. 1999;56(2):244. doi:10.1001/archneur.56.2.244