Background

Around 3,500 people will suffer an OHCA in Scotland, with survival rates of around 1 in 20 (Scottish Government, 2015). The accurate prognosis of these patients is important to avoid unnecessary treatment (Sandroni et al 2014). EEG is used in the prognosis of these patients (Deng, Xiong & Jia, 2015), although there is no clear agreement as to what the important prognostic features are (Amorim et al, 2015). The aim of this study is to evaluate the predictive value of EEG carried out post OHCA and identify other potential prognostic markers.

Methods

A retrospective audit was carried out, reviewing the EEG findings of patients over a year long period at the neurophysiology department in Glasgow. All patients were included who suffered an OHCA, were over the age of 18, had not regained consciousness and did not have any previously known EEG abnormality. Patients were excluded who had died due to any other co-morbidity and patients on sedation at the time of testing were excluded from the EEG part of the analysis. EEG findings were grouped depending on the overriding features of the EEG and deemed either “malignant” or “benign”. These groups were then compared to the survival rates. Other prognostic features reviewed were the patients’ age, gender, downtime and cause of the OHCA.

Results

The EEG findings (n=26) correlated with mortality rates, with those patients having a malignant EEG type having a higher mortality rate (93.3%) than those with a benign EEG type (54.5%) (p=0.054). The cause of OHCA (n=18) also correlated with mortality rates, with 50% of those having a cardiac cause surviving compared to none with a non-cardiac cause (p=0.054). None of the other variables analysed had any significant correlation to the patient’s outcome.

Discussion

This study has demonstrated that the EEG is a helpful prognostic indicator in patients post OHCA. Malignant features, including suppression, burst suppression, and persistent complex activity were identified as having a strong correlation with poor prognosis. Demonstrating this correlation validates the usefulness of EEG post OHCA and may help shape the way neurophysiologists report their findings, with a view to making these reports more consistent and accessible. This may help to ensure that patients are treated appropriately and that family members receive a prompt and accurate prognosis. The study also confirmed previous research, that those with a cardiac cause are more likely to survive their hospital admission (Claesson, et al, 2017).