Intraoperative monitoring with somatosensory evoked potentials in carotid artery surgery--less reliable in patients with preoperative neurologic deficiency?
BACKGROUND
In a retrospective analysis of intraoperative somatosensory evoked potential (SEP) results during carotid artery surgery we found some cases with postoperative neurologic deficits, surprisingly without significant SEP changes.


METHODS
Median nerve SEP were monitored as usual. Indication for selective shunting was a complete loss of amplitude N20/P25 in the first period of the investigation, later on a 50% reduction, or a prolongation of the central conduction time (CCT) of about 1.5 ms after cross-clamping. Anaesthesia was maintained with isoflurane in N2O/O2, fentanyl and atracurium.


RESULTS
Over a 3-year period 146 patients were monitored. Indications were: transient ischaemic attacks (TIA) (n=51), stroke (n=23), stroke with residuals (n=39), asymptomatical stenosis (n=29), subclavian steal syndrome (n=4). Twenty-four patients received an intraluminal shunt following SEP alterations. Postoperatively, 5 patients (3.4%) had symptoms of intraoperative brain ischaemia (stroke n=2, TIA n=3), 4 of them showing only minor intraoperative SEP alterations; 1 received a shunt because of CCT prolongation. Four of these 5 patients had cerebral neurologic deficiency preoperatively.


CONCLUSIONS
Since some authors have found a 100% sensitivity of intraoperative SEP, it is remarkable, that 1 patient with postoperative stroke and 3 patients with TIA had no significant SEP changes intraoperatively. We suppose there was an association with preoperative neurological deficits resulting from previous strokes. In such cases, regional critical ischaemia may apparently occur outside the sensory pathway monitored with SEP.
Linstedt
U
U
Clinic of Anaesthesiology and Intensive Care Medicine, Christian Albrechts University of Kiel, Germany.
Maier
C
C
Petry
A
A
D000368:Aged; D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D001166:Arteriovenous Shunt, Surgical; D001279:Atracurium / Q000008:administration & dosage; D002545:Brain Ischemia / Q000209:etiology; D002315:Cardiopulmonary Bypass; D016893:Carotid Stenosis / Q000503:physiopathology / Q000601:surgery*; D002561:Cerebrovascular Disorders / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery; D016894:Endarterectomy, Carotid / Q000009:adverse effects; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage; D006801:Humans; D007431:Intraoperative Complications; D002546:Ischemic Attack, Transient / Q000503:physiopathology / Q000601:surgery; D007530:Isoflurane / Q000008:administration & dosage; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009431:Neural Conduction; D009434:Neural Pathways / Q000503:physiopathology; D003473:Neuromuscular Nondepolarizing Agents / Q000008:administration & dosage; D009475:Neurons, Afferent / Q000502:physiology; D009609:Nitrous Oxide / Q000008:administration & dosage; D010100:Oxygen / Q000008:administration & dosage; D011183:Postoperative Complications; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013349:Subclavian Steal Syndrome / Q000503:physiopathology / Q000601:surgery
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D003473:Neuromuscular Nondepolarizing Agents; D001279:Atracurium; D007530:Isoflurane; D009609:Nitrous Oxide; D010100:Oxygen; D005283:Fentanyl