Abstract Body: Introduction: Sepsis and septic shock remain global healthcare issues associated with high mortality rates affecting millions every year despite best care efforts. Activation of the renin-angiotensin-system (RAS) is an early event in sepsis, and renin levels may more strongly associate with mortality than serum lactate, a widely accepted index of patient status. We postulated that reduced levels of Angiotensinogen (AGT) may reflect a dysfunctional RAS driven by high renin levels but an attenuated expression of Ang II to adequately support tissue perfusion and blood pressure. This study compared the association with mortality of AGT to serum lactate and active renin in a subset of the VICTAS (Vitamin C, Thiamine, and Steroids in Sepsis) cohort (N=103) at baseline (day 0) prior to treatment.

Methods: Serum levels of intact AGT and active renin protein were quantified by separate ELISAs. Biomarker discrimination for all-cause 30-day mortality was compared by receiver operating characteristic (ROC) curves generated by logistic regression models adjusted for age, sex, sequential organ failure assessment (SOFA) score, systolic blood pressure, and in-hospital vasopressor support. Association of serum AGT, renin, and lactate with mortality was assessed by Kaplan-Meier curves with log rank test and hazard ratios derived from Cox regression.

Results: Median [interquartile range] serum levels for AGT were: 114 [78.2-205.4] nM; renin: 4.9 [2.2-13.6] pM; and lactate: 2.6 [1.7-3.8] mM. ROC curves revealed better discrimination of AGT for mortality than either active renin or lactate. The area under the curve (AUC) of AGT (0.82, 95% CI: 0.70, 0.93) was greater than lactate (AUC=0.68, 95% CI: 0.57, 0.80; p=0.022). Kaplan-Meier curves and log rank test also revealed that AGT levels below 114 nM associated with reduced survival. Renin levels greater than 4.9 pM were also associated with patient mortality albeit less than that for AGT while higher lactate levels (>2.6 mM) were not associated with mortality in this cohort.

Conclusion: AGT levels more strongly associated with 30-day mortality than renin or lactate in the VICTAS cohort. Reduced AGT may reflect increased consumption by high renin coupled with reduced expression by the liver ultimately impairing Ang II-AT₁R tone in critically ill patients. The prospective assessment of circulating AGT may facilitate more precise therapeutic approaches treatment to restore a dysfunctional RAS and improve overall mortality in sepsis.