Ultra-early short- and middle-latency SSEP accurately predict good and poor outcome after cardiac arrest

Background: Accurate prognostication following cardiac arrest (CA) is crucial for informing clinical decisions. Current guidelines do not recommend a specific time point for recording somatosensory evoked potentials (SSEPs) after CA. We evaluated the ability of ultra-early short- and middle-latency SSEPs to predict good an poor neurological outcome and compared its accuracy with that of other predictors recorded early after CA. Methods: Prospective single-centre study. Sixty-five comatose adults underwent a multimodal prognostic assessment, including neurophysiological (SSEPs and electroencephalogram [EEG]), clinical (pupillary reflexes and myoclonus), and imaging indices (brain computed tomography [CT]) within 6 h post-CA. Serum neuron-specific enolase (NSE) was sampled 12 h post-CA. We analysed the SSEPs N20 wave amplitude and duration, and the presence of the middle-latency N70 wave. Poor outcome was defined as a Cerebral Performance Category (CPC) of 3–5 at hospital discharge. Results: A bilaterally absent N20 wave predicted poor outcome with 100[89–100]% specificity and 67[48–82]% sensitivity. Adding low-amplitude (<1.2 µV), prolonged (>10 ms) N20 waves without N70 increased sensitivity to 93[79–99]% without compromising specificity. Conversely, a high-amplitude (>3 µV) N20 wave with normal duration with preserved N70 predicted good outcome with 94[79–99]% sensitivity and 100[89–100]% specificity. SSEPs outperformed all other early prognostic indices for both good and poor outcome prediction. All poor outcome patients had at least two concordant unfavourable predictors. Conclusions: Ultra-early quantitative assessment of short- and middle-latency SSEPs provides highly accurate prediction of both good and poor neurological outcomes after CA. This approach may enhance early clinical decision-making and warrants validation in larger cohorts.