Plasma DNA is likely to be released from damaged and inflamed tissues, and in this context it might act as a marker of early outcome of patients with hypoxic-ischemic encephalopathy after cardiac arrest. We have demonstrated a role for plasma DNA as an early predictor of mortality in patients after cardiac arrest. Thus, the ability for rapid risk stratification of survival may allow clinicians to make more rational therapeutic decisions.Moderate increases in plasma in plasma DNA may be associated with the chronic inflammatory response to atherosclerotic process which often occurs in elderly patients [28]. In our study there was no difference with respect to cardiovascular risk factors or chronic comorbidities except for diabetes within survivors and non-survivors patients and when entered into the logistic regression model for hospital mortality the adjusted odds ratio was not significant. Therefore it is likely that differences in plasma DNA levels in our study reflect the acute event of cardiac arrest rather than chronic illness.Tissue hypo-perfusion during the early phase of post-cardiac arrest induces an increase in serum lactate because of anaerobic glycolisis. We have found that cell-free plasma DNA concentration at inclusion correlated significantly with initial lactate concentrations and maximum lactate concentrations within a 24-hour period, which may reflect the effect of tissue hypoxia on apoptotic or necrotic cell death. Effective lactate clearance which likely reflects improved tissue perfusion is associated with decreased mortality in severe sepsis and other critical-care patient populations [29,30]. Two studies have reported that post-cardiac arrest patients with more effective lactate clearance had improved survival [7,8]. Similarly, the current study revealed that lactate clearance at six hours was significantly higher in survivors compared to non-survivors at 24 hours, but we did not find this variable to be an independent predictor for early or late mortality when entered into the multivariable analysis. Further studies are required to establish the independent predictive value of effective lactate clearance after cardiac arrest.An increase in plasma DNA concentration in critically ill patients may be also due to a decrease in clearance efficiency. The clearance mechanism of DNA from the circulation is poorly understood [31]. In mice, nucleotides are mainly cleared by liver [32]. Approximately 0.5 to 2% of circulating plasma DNA crosses the kidney barrier and is excreted into urine [33]. We found that serum urea or creatinine were not independently associated with plasma DNA concentrations, which is consistent with data from experimental studies.