The impact of soluble interleukin-2 receptor as a biomarker of delirium

Biomarkers might help to predict the emergence of delirium. Advance warning of the threats of this condition could potentially reduce significant morbidity, mortality, and costs of hospitalizing patients.

Our prospective study investigates for the first time the impact of soluble interleukin-2 receptor (sIL-2R) as a biomarker of delirium after cardiac surgery with cardiopulmonary bypass (CPB).

A total of 34 patients who underwent elective cardiac surgery with CPB were enrolled. During the intensive care unit (ICU) stay and after discharge from the ICU, the delirious state was evaluated daily using the Delirium Rating Scale by Trzepacz. sIL-2R was assayed before CPB, 24 hours postoperatively, and on the day before discharge.

After CPB, 11 patients (32.4%) developed delirium. A short-term delirious state (less than 1 day) was observed in 3 patients and a prolonged delirious state in 8 patients. During the study period, sIL-2R levels decreased 24 hours postoperatively and increased afterward (Friedman test; p < 0.001). As shown by the Spearman rank correlation, CPB patients with higher Delirium Rating Scale scores 72 hours, 96 hours, and 120 hours postoperatively had significant higher sIL-2R levels 24 hours postoperatively. In CPB patients with a prolonged postoperative delirious state, the sIL-2R level is statistically significantly elevated 24 hours postoperatively in comparison with CPB patients without a postoperative delirium (Mann-Whitney U: 48.5, p = 0.049).

High levels of sIL-2R appear to be a useful biomarker to identify patients with high risk for a delirious state.