The effect of sedation and time after cardiac arrest on coma outcome prognostication based on EEG power spectra

Abstract

Early prognostication of long-term outcome of comatose patients after cardiac arrest remains challenging. Electroencephalography-based power spectra after cardiac arrest have been shown to help with the identification of patients with favourable outcome during the first day of coma. Here, we aim at comparing the power spectra prognostic value during the first and second day after coma onset following cardiac arrest and to investigate the impact of sedation on prognostication. In this cohort observational study, we included comatose patients (N = 91) after cardiac arrest for whom resting-state electroencephalography was collected on the first and second day after cardiac arrest in four Swiss hospitals. We evaluated whether the average power spectra values at 4.6-15.2 Hz were predictive of patients' outcome based on the best cerebral performance category score at 3 months, with scores ranging from 1 to 5 and dichotomized as favourable (1-2) and unfavourable (3-5). We assessed the effect of sedation and its interaction with the electroencephalography-based power spectra on patient outcome prediction through a generalized linear mixed model. Power spectra values provided 100% positive predictive value (95% confidence intervals: 0.81-1.00) on the first day of coma, with correctly predicted 18 out of 45 favourable outcome patients. On the second day, power spectra values were not predictive of patients' outcome (positive predictive value: 0.46, 95% confidence intervals: 0.19-0.75). On the first day, we did not find evidence of any significant contribution of sedative infusion rates to the patient outcome prediction (P > 0.05). Comatose patients' outcome prediction based on electroencephalographic power spectra is higher on the first compared with the second day after cardiac arrest. Sedation does not appear to impact patient outcome prediction.

Keywords: EEG; cardiac arrest; coma; early prognostication; sedation.

Graphical Abstract

Figure 1

Power spectra for patients on Days 1 and 2 after coma onset. Normalized power spectra frequencies, averaged across patients and across electrodes, in arbitrary units for patients in the training set of one representative fold with FO, blue line and UO, pink line for Days 1 and 2 (N = 73). On Day 1, differences were observed across the whole electrode montage and especially between 4.6 and 15.2 Hz (cluster permutation statistical analysis, P < 0.05, two-tailed). Topographical insets illustrate the difference in power spectra between FO and UO in the frequency range between 4.6 and 15.2 Hz

Figure 2

Prognostication of coma outcome based on power spectra on Days 1 and 2 after coma onset. Outcome prediction based on normalized spectral power in arbitrary units for Days 1 and 2. Blue dots show patients in the training set for one representative fold with FO; N = 36, pink dots show patients in the training with UO; N = 37 and black dots show patients belonging in the test set for one representative fold (FO: N = 9; UO: N = 9). The dashed line indicates the threshold for outcome prediction; values above the threshold should predict FO. For Day 1, in the subset of patients recorded on both days, we correctly predicted FO in 18 patients without false positives. For Day 2, applying the same threshold as Day 1, we found no significant outcome prediction