Predictive Value Of A New Warning Criterion (Ischemia Tolerance Ratio) In SEP Monitoring During Intracranial Aneurysm Surgery: A Randomized Trial And Cohort Study

ObjectiveWe assessed a new warning criterion with higher sensitivity andspecificity than common warning criteria (50%amplitude declinecomparing with baseline) of SEPs.MethodsIn this randomized, double-blind, common criteria-controlled study, werandomly assigned patients with intracranial aneurysms and SEPsmonitoring into three groups. In group Ⅰ, the warning criterion is thecommon criteria at present, the50%amplitude reduction of SEPscomparing with baseline. In group Ⅱ, the warning criteria is theIschemia Tolerance Ratio (ITR) being equal to50%, and80%in groupⅢ. The outcome measures included postoperative motor or sensorydeficits, new cerebral infarction （examined by computed tomographicscans）. And the sensitivity, specificity, PPV, NPV and characteristics ofparticipants were analyzed by SPSS software. ResultsIn group Ⅰ, all except one didn’t suffer from neurological deficits. Andthe sensitivity was92.3%, while specificity was50.0%. In group Ⅱ,there was no infarction for all patients. In group Ⅲ, all patients gotpostoperative neurological deficits. The sensitivity was92.3%, andspecificity was100%, much higher than that of group Ⅰ.ConclusionIschemia Tolerance Ratio (ITR), with higher specificity than commonwarning criteria (50%amplitude reduction of SEPs), can illustrate therelationship between ischemic changes and postoperative neurologicaldeficits and be employed as a new warning criteria of SEPs.