Renin Levels and Angiotensin II Responsiveness in Vasopressor-Dependent Hypotension.

OBJECTIVES: The relationship between renin levels, exposure to renin-angiotensin system (RAS) inhibitors, angiotensin II (ANGII) responsiveness, and outcome in patients with vasopressor-dependent vasodilatory hypotension is unknown. DESIGN: We conducted a single-center prospective observational study to explore whether recent RAS inhibitor exposure affected baseline renin levels, whether baseline renin levels predicted ANGII responsiveness, and whether renin levels at 24 hours were associated with clinical outcomes. SETTING: An academic ICU in Melbourne, VIC, Australia. PATIENTS: Forty critically ill adults who received ANGII as the primary agent for vasopressor-dependent vasodilatory hypotension who were included in the Acute Renal effects of Angiotensin II Management in Shock study. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: After multivariable adjustment, recent exposure to a RAS inhibitor was independently associated with a relative increase in baseline renin levels by 198% (95% CI, 36-552%). The peak amount of ANGII required to achieve target mean arterial pressure was independently associated with baseline renin level (increase by 46% per ten-fold increase; 95% CI, 8-98%). Higher renin levels at 24 hours after ANGII initiation were independently associated with fewer days alive and free of continuous renal replacement therapy (CRRT) (-7 d per ten-fold increase; 95% CI, -12 to -1). CONCLUSIONS: In patients with vasopressor-dependent vasodilatory hypotension, recent RAS inhibitor exposure was associated with higher baseline renin levels. Such higher renin levels were then associated with decreased ANGII responsiveness. Higher renin levels at 24 hours despite ANGII infusion were associated with fewer days alive and CRRT-free. These preliminary findings emphasize the importance of the RAS and the role of renin as a biomarker in patients with vasopressor-dependent vasodilatory hypotension.

Exploring the norepinephrine to angiotensin II conversion ratio in patients with vasodilatory hypotension: A post-hoc analysis of the ARAMIS trial.

PURPOSE: Angiotensin II is approved for catecholamine-refractory vasodilatory shock but the conversion dose ratio from norepinephrine to angiotensin II remains unclear. METHODS: We conducted a post-hoc analysis of the Acute Renal effects of Angiotensin II Management in Shock (ARAMIS) trial involving patients with vasodilatory hypotension. We determined the norepinephrine equivalent dose immediately prior to angiotensin II initiation and calculated the conversion dose ratio between norepinephrine and angiotensin II. We performed subgroup analyses based on recent exposure to angiotensin receptor blockers (ARBs) and renin levels at baseline. RESULTS: In 37 patients, the median conversion dose ratio between norepinephrine equivalent and angiotensin II was to 10:1 for norepinephrine bitartrate (5:1 for norepinephrine base). The conversion ratio was not affected by the baseline renin, with a median ratio of 10 (7-21) in the high renin group versus 12 (5-22) in the low renin group. Finally, exposure to ARBs prior admission appeared to diminish the conversion ratio with a median ratio of 7 (4-13) in ARB patients vs. 12 (7-22) in non-ARB patients. CONCLUSIONS: The norepinephrine to angiotensin II conversion dose ratio is 10:1 in a vasodilatory hypotension population. These findings can guide clinicians and researchers in the use, dosing, and study of angiotensin II in critical care.

A PILOT STUDY OF ANGIOTENSIN II AS PRIMARY VASOPRESSOR IN CRITICALLY ILL ADULTS WITH VASODILATORY HYPOTENSION: THE ARAMIS STUDY.

ABSTRACT: Objective: The aim of the study is to evaluate the efficacy and safety of using angiotensin II (Ang2) as primary vasopressor for vasodilatory hypotension. Methods: This was a prospective observational study of critically ill adults admitted to an academic intensive care unit (ICU) with vasodilatory hypotension. We treated 40 patients with Ang2 as primary vasopressor and compared them with 80 matched controls who received conventional vasopressors (norepinephrine, vasopressin, metaraminol, epinephrine, or combinations). Results : Mean age was 63 years and median Acute Physiology and Chronic Health Evaluation III score was 65. Ang2 patients had lower ICU mortality (10% vs 26%, P = 0.04); however, their 28- and 90-day mortality was not significantly different (18% vs 29%, P = 0.18; 22% vs 30%, P = 0.39). Peak serum creatinine levels were similar (128 vs 126 µmol/L, P = 0.81), as was the incidence and stage of acute kidney injury (70% vs 74%, P = 0.66), requirement for continuous renal replacement therapy (14% vs 13%, P = 0.84), and risk of major adverse kidney events at 7 days (20% vs 29%, P = 0.30). However, Ang2 patients with prior exposure to renin angiotensin aldosterone system inhibitors had a lower peak serum creatinine ( P = 0.03 for interaction) than conventional vasopressors patients, and serum troponin elevations were less common with Ang2 (8% vs 22%, P = 0.04). The incidence of thromboembolic complications was similar. Conclusions: Primary Ang2 administration in vasodilatory hypotension did not seem harmful compared with conventional vasopressors. Although Ang2 did not decrease peak serum creatinine levels or major adverse kidney events, its effects on intensive care unit survival, serum troponin, and renal function in patients on renin angiotensin aldosterone system inhibitors warrant further exploration in randomized trials (ACTRN12621000281897).