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International Angiology 1998 March;17(1):10-4


language: English

Intraoperative assessment of cerebral ischaemia during carotid surgery

Pedrini L., Tarantini S., Cirelli M. R., Ballester A., Cifiello B. I., D’addato M.

From the Institute of Vascular Surgery, University of Bologna, Bologna, Italy


Background. This study aimed to eval­u­ate the reliabi-lity of som­a­tos­en­so­ry ­evoked poten­tials (SEPs) in iden­ti­fy­ing clamp­ing ischae­mia dur­ing carot­id sur­gery under gen­er­al anaesthe­sia.
Methods. We ­reviewed the ­records of 196 con­sec­u­tive carot­id endar­te­rec­to­mies (CEA) per­formed under gen­er­al anaesthe­sia, out of 1550 ­patients oper­at­ed on ­between 1975 and 1993. SEPs were mon­i­tored after con­tro­lat­er­al ­median nerve stim­u­la­tion at the wrist in all ­patients. Moreover they ­received an intra­ve­nous bolus of 2500 IU of hep­ar­in and the stump pres­sure was meas­ured. A com­ple­tion angio­gra­phy was per­formed in all ­patients. An intra­lu­mi­nal shunt was insert­ed when the ampli­tude of the N20-P25 SEPs com­plex ­decreased by more than 50% of pre-clamp­ing value (path­o­log­ic SEPs) or when a pre­op­er­a­tive CT-scan ­showed an ischaem­ic area in the con­tra­lat­er­al hem­i­sphere. In some ­patients the shunt was not insert­ed ­because of tech­ni­cal dif­fi­cul­ties or ­because the path­o­log­i­cal SEP com­plex ­decrease devel­oped when the ­suture of the arter­i­ot­o­my was ­almost com­plete.
Results and con­clu­sions. As the pre­clamp­ing ampli­tude (Ab) of N20-P25 was extreme­ly var­i­able, rang­ing from 0.9 and 7.5 µV, we adopt­ed the ratio: ∆A=(At-Ab)/Ab (At=ampli­tude meas­ured dur­ing clamp­ing every 2 min at time t). Mean ­decrease of ∆A meas­ured in the whole group ­ranged ­between 15% and 20%, but mean ∆A val­ues in ­patients with path­o­log­i­cal SEPs were ­around 60%. Even ­patients with pos­i­tive CT-scans or with a back-pressure lower than 50 mmHg devel­oped a mean ∆A ­decrease of about 20%. A path­o­log­i­cal SEP was ­present in 50 ­patients, but devel­oped in only 12 dur­ing the clamp­ing trial. An intra­lu­mi­nal shunt was insert­ed in 22 cases; the other ­patients ­received phar­mac­o­log­i­cal treat­ment with anaesthet­ic or vasoac­tive drugs. Among the ­patients with path­o­log­i­cal SEPs, 3 pre­sent­ed post­op­er­a­tive symp­toms relat­ed to carot­id cross-clamp­ing; only 1 of these was shunt­ed but with­out SEPs nor­mal­isa­tion. No ­patients with nor­mal SEPs devel­oped a post­op­er­a­tive neu­ro­log­i­cal def­i­cit, giv­ing a reli­abil­ity of 86.7%, a sen­si­tiv­ity of 100% and a spec­i­fic­ity of 86.5%.

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