We compared the demographic and clinical characteristics of the study population between two groups: patients who had a good neurological outcome (CPC 1-2) and patients who had a poor neurological outcome (CPC 3-5) after cardiac arrest (CA). We performed this comparison for all patients (; Table 1) and also separately for men () and women (; Supplementary Table 2). Out of the total study population, 81% were men and 49% had a poor neurological outcome. We found that patients who had a poor neurological outcome were older than those who had a good neurological outcome. They also had more comorbidities, such as hypertension, diabetes, and coronary artery disease. Moreover, they had a longer time interval between CA and return of spontaneous circulation (ROSC), and higher initial levels of serum lactate, which indicate tissue hypoxia. On the other hand, they received bystander CPR less frequently than those who had a good neurological outcome. Additionally, we observed that a higher proportion of patients who had a poor neurological outcome presented with shock at admission, which is a sign of hemodynamic instability, and had an initial nonshockable rhythm, such as pulseless electrical activity or asystole, which are associated with lower survival rates. There was no significant difference between men and women in terms of these characteristics (Supplementary Table 2).
We also analyzed the association between serum lactate levels and neurological outcome. We categorized the patients into four groups based on their initial serum lactate levels: 12 mmol/L. We found that higher serum lactate levels were associated with lower rates of good neurological outcome. The odds ratio for good neurological outcome was 0.36 (95% confidence interval [CI] 0.24-0.54) for patients with serum lactate levels of 4-8 mmol/L, 0.16 (95% CI 0.10-0.26) for patients with serum lactate levels of 8-12 mmol/L, and 0.07 (95% CI 0.04-0.13) for patients with serum lactate levels of >12 mmol/L, compared to patients with serum lactate levels of 12 mmol/L, compared to patients with serum lactate levels of 061ffe29dd