P329 Repeatability of SSEPs during and after targeted temperature management

Abstract

Objectives In patients treated with mild therapeutic hypothermia after cardiac arrest, a bilateral absent cortical SSEP response (N20) at day 3 is a reliable predictor of poor neurological outcome. Little is known about the effect of hypothermia on the SSEP and the reliability of this prognostic marker in an earlier stage. We evaluated the N20 response during the first 5 days of ICU admission. Methods In a prospective cohort of 58 patients with postanoxic coma, treated with mild therapeutic hypothermia, the SSEP was measured once a day during the first 5 days of ICU admission. The SSEP at day one was performed within 12 h after cardiac arrest. Presence of the N20 response was retrospectively evaluated. Clinical outcome at six months was classified by the Cerebral Performance Category scale (CPC), dichotomized as good (CPC 1–2) or poor (CPC 3–5). Results In none of the eight patients with an absent SSEP at day one (during hypothermia), the SSEP returned during later days. All eight patients had poor neurological outcome. In patients with a present cortical response at day one, the N20 remained present during later days. The sensitivity for prediction of poor outcome was 23% with a specificity of 100%. During hypothermia, the latency of the N20 was prolonged by 2–4 ms. Discussion In this pilot study, SSEPs are stationary during the first 5 days after cardiac arrest: no differences are observed between presence or absence of responses at day one during treatment with mild therapeutic hypothermia and hereafter. Although an absent N20 is a reliable predictor for poor neurological outcome its sensitivity is low. Conclusions The presence or absence of the cortical N20 response is stable during the first 5 days in patients after cardiac arrest treated with hypothermia. Significance A bilateral absent SSEP at day one might be a reliable predictor of poor neurological outcome.