The Importance of Plasma Renin Concentrations in Intensive Care Patients with Circulatory Shock

Background: Renin is a hypoperfusion marker and a good index of renin–angiotensin–aldosterone system (RAAS) activity. The purpose of this study was to evaluate whether the plasma renin concentration (PRC) can represent a tissue perfusion marker for predicting mortality in patients with circulatory shock in intensive care. Methods: This prospective study included patients aged 18 years or older who were hospitalized in the intensive care unit (ICU). A total of 69 patients were enrolled, of whom 37 had circulatory shock and were all diagnosed with septic shock according to Sepsis-3 criteria, while 32 patients did not have shock. Patient groups were compared, and survival analysis was carried out. Mortality predictions of PRC, lactate and combined tests (including PRC, mottling scores, central venous saturation of oxygen, C-reactive protein, procalcitonin, and lactate) were investigated with ROC analysis. Results: ICU 28-day mortality was 36.2% (n = 25) and was significantly higher in patients with circulatory shock than those without (CS:21, 56.8% vs. NS:4, 12.5%, respectively, p < 0.001). The survival was significantly higher in patients without circulatory shock than those with shock (17 vs. 16 days; p = 0.038). The increase in mottling score (HR: 1.64 [95%CI: 1.15–2.33]; p < 0.01) and PRC (HR = 1.01 [95%CI: 1.00–1.02]; p < 0.05) levels and the decrease in glomerular filtration rate (GFR) (HR = 0.98 [95%CI: 0.96–0.99]; p < 0.05) were associated with decreased survival times in the ICU patients (p < 0.001). Combined tests yielded better prediction of mortality than PRC level alone. Conclusions: PRC may reflect circulatory shock and predict survival in critically ill patients; however, larger prospective studies incorporating serial PRC measurements are needed before it can be recommended as an independent biomarker of mortality.