Jm. Guerit et al., SOMATOSENSORY-EVOKED POTENTIAL MONITORING IN CAROTID SURGERY .1. RELATIONSHIPS BETWEEN QUALITATIVE SEP ALTERATIONS AND INTRAOPERATIVE EVENTS, Electroencephalography and clinical neurophysiology. Evoked potentials, 104(6), 1997, pp. 459-469
This paper presents the results of intraoperative median nerve SEP mon
itoring in 205 successive patients undergoing isolated carotid endarte
rectomy (CE) (N = 172) or CE followed by coronary bypass (CBP) and/or
vascular replacement (VR) (N = 33). The left and right median nerves w
ere alternately stimulated and recordings performed on 4 channels: cer
vical, ipsi-and contralateral parietal, and frontal. SEPs were qualita
tively rated in terms of mild, moderate, or severe ipsilateral, contra
lateral, or bilateral abnormalities. The SEP abnormalities were subdiv
ided into 5 categories as a function of their relationships with intra
operative events: no alterations (67.3%), early or late SEP alteration
s after carotid cross-clamping (15.6%), SEP alterations after a drop i
n blood pressure (occurring outside of or within the cross-clamping pe
riod) (15.1%), SEP alterations of a most likely embolic origin (2.4%),
SEP changes after head positioning (1%), and SEP changes after a modi
fication of the anesthetic regimen (1.5%). Only moderate to severe SEP
alterations occurring soon after carotid crossclamping justified shun
t installation in 16% of the cases. SEP alterations after a drop in bl
ood pressure were reversed merely by restoring blood pressure. The neu
rological outcome was uneventful in 94.2% of cases. Of the 12 patients
who developed neurological sequellae, only one case presented transie
nt sequellae after isolated CE without SEP changes white most cases ei
ther had undergone combined CE and CBP and/or VR (6 cases) or had pres
ented SEP alterations of embolic origin (3 cases). We conclude that ou
r system of qualitative rating of SEPs proved very sensitive to intrao
perative hemodynamic disturbances or macroembolisms. (C) 1997 Elsevier
Science Ireland Ltd.