Neuroendocrine Balance Index: an Indicator of Metabolic Response to Surgical Stress in Cardiac Surgery

Aim. To analyse the dynamics of the Neuroendocrine Balance Index (NEBI = ln(Cortisol/PRL)) during the perioperative period of coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) in order to evaluate its potential as an integrative marker of metabolic response to surgical stress. Materials and Methods. The study included 32 patients (mean age 63.6±1.4 years) who underwent minimally invasive CABG with CPB. Serum cortisol and prolactin levels were measured at three stages: before CPB (T1), immediately after CPB (T2), and on postoperative days 2-3 (T3). The NEBI and its standardised values (NEBI z-score) were calculated. Statistical analysis involved the Friedman test with pairwise Wilcoxon comparisons (Bonferroni correction) and a mixed linear model with the surgical stage (Stage) as a fixed factor. Categorical variables were analysed using the extended Fisher’s exact test. Results. A phased hormonal response to surgical stress was demonstrated. Before surgery, the cortisol-dependent component predominated (NEBI z-score =+0.68 SD). After CPB, a shift toward prolactin dominance was observed (NEBI z-score=-0.22 SD), which persisted during the early postoperative period (NEBI z-score=-0.47 SD). By stage T3, cortisol levels tended to decrease below the lower reference limit, suggesting the development of relative adrenal insufficiency. Moderate prolactin predominance at this stage appeared to have an adaptive role, limiting the excessive catabolic effect of cortisol (F(2;52.9) = 17.51; p<0.001). Conclusions. The Neuroendocrine Balance Index represents a promising integrative marker for assessing the metabolic direction of the stress response in cardiac surgery. Its dynamics reflect the transition from the catabolic to the anabolic recovery phase and allow evaluation of the patient’s adaptive reserve. Monitoring NEBI during the postoperative period may support personalised assessment of stress resistance and early detection of metabolic instability.