Anesthésie et recherche clinique
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Intraoperative Evoked Potentials: A Review of Clinical Impact and Limitations

Ana Sofia Marafona, Humberto S Machado

Background: Nowadays, intraoperative evoked potentials are recommended in a variety of procedures but there is still a lack of standard protocols and consensus about warning criteria. Moreover, studies are now being made to fundament its risk-beneficial ratio through recordings’ predictive value for short and long term outcomes. Furthermore, wake up test limitations encouraged intraoperative evoked potentials research, a reliable monitoring technology.
Objectives: This literature revision aims to acknowledge last decade intraoperative evoked potentials technological advances and fundament its clinical impact in multiple contexts.
Methods: A literature review based on clinical series from 2007 to June 2017.
Results: Combined intraoperative evoked potentials sensitivity and specificity of IONM for sensory motor impairment was 100 and 98%, respectively. SSEP (somatosensory evoked potentials) and MEP (motor evoked potentials) responses successfully recognize sensory and motor cortex, 91% and 99%, correspondingly. Upon that, combined monitoring modalities are considered essential since they can limit unnecessary morbidity. In series, 3.83% of recordings were altered and 44.44% reversible. Despite requiring predictive factors for neurological injury identification, reversibility and decreased duration of altered waveform indicates a favorable outcome, based on presentation and discharge evaluation. In opposition, irreversibility of signal’s deterioration is related to a decrease on Glasgow outcome scale at long-term follow up. At last, intraoperative evoked potentials demonstrated high sensitivity, specificity and negative predictive value.
Conclusions: Intraoperative evoked potentials have a role as an adjuvant-monitoring tool. Risk-beneficial studies recommend its use in surgeries with known risk of neurological injury. Furthermore, surgical procedures are more accurate and integrity of neurologic pathways better preserved when real time monitored is used. As a result, outcomes tend to be better and more predictable. Nevertheless, standardized protocols, warning signals criterion and specialized teams with adequate communication are still required in order to accurately detect waveform deterioration and exclude artifacts.