Changes in neuron-specific enolase are more suitable than its absolute serum levels for the prediction of neurologic outcome in hypothermia-treated patients with out-of-hospital cardiac arrest.

Background: To determine neurologic outcome in patients with out-of-hospital cardiac arrest (OHCA) and treatment with mild therapeutic hypothermia (MTH).

Methods: Seventy-three consecutive OHCA patients treated with MTH were retrospectively analyzed. Serum neuron-specific enolase (NSE) was measured 24, 48, and 72 h after admission. In patients with no motor response 48 h after termination of analgosedation (n = 40), clinical neurological examination and evoked potentials (EPs) were determined. Neurological outcome was assessed after 2 months based on the cerebral performance categories (CPC), and categorized as good (CPC 1-3) or poor (CPC 4 and 5).

Results: Forty-three patients had a CPC score of 1-3 and 30 patients had a CPC 4-5. The best predictive value for poor neurologic outcome was an increase of NSE by ≥4.3 ng/mL between day 1 and day 2 (sensitivity 80 %, specificity 100 %, positive predictive value (PPV) 100 %, negative predictive value 86 %). Absolute NSE values were less reliable in the prediction of poor outcome with the highest sensitivity (88 %) and specificity (95 %) if values reached ≥36.3 ng/mL on day 3. Somatosensory EPs (SSEPs) showed a specificity of 100 % and PPV of 100 %; however, sensitivity for evoked potentials was low (29 %). Intriguingly, two initially comatose patients with excessive NSE values (24 h NSE: 101 and 256 ng/mL, and 48 h NSE: 93 and 110 ng/mL, respectively) had physiological SSEPs and regained a CPC score of 1.

Conclusion: In patients treated with MTH after OHCA changes in NSE are more suitable than its absolute serum levels for the prediction of poor neurologic outcome. Since unequivocal prediction of poor neurologic outcome is of utmost importance in these patients the decision to limit therapy must be based on several prediction tools with the highest PPV and specificity including SSEPs.