BACKGROUND: No standardized index exists to assess cardiovascular responsiveness to angiotensin-II. We hypothesized that a standardized index of initial blood pressure response to angiotensin-II treatment would be associated with clinical outcomes. METHODS: Using data from the Angiotensin Therapy for High Output Shock (ATHOS-3) trial, we developed an Angiotensin-II Initial MAP Response Index of Treatment Effect (AIMRITE) defined as (MAP at hr1 - MAP at baseline)/study drug dose. We assessed AIMRITE continuously and, based on observed distributions, we additionally categorized patients as "responsive" or "resistant", with responsiveness defined by an AIMRITE ≥ 0.90 mmHg/ng/kg/min. The primary clinical outcome was 28-day mortality. Secondary outcomes included days alive and vasopressor- or ventilator- or renal replacement therapy-free at day-7. Biological outcomes included baseline renin, angiotensin-II, and renin/angiotensin-II ratio, and their change at hr3. RESULTS: Of 158 placebo patients, as expected, 157 (99%) had AIMRITE <
0.90 mmHg/ng/kg/min (median AIMRITE 0.02
IQR - 0.03-0.10). In contrast, 163 patients assigned to angiotensin-II had a median AIMRITE of 1.43 mmHg/ng/kg/min (IQR 0.35-2.83). Of these, 97 (60%) were responsive (median AIMRITE 2.55
IQR 1.66-4.12) and 66 (40%) were resistant (median AIMRITE 0.24
IQR 0.10-0.52). Each 1.0-unit increase in AIMRITE was associated with a 16% lower hazard of death (HR: 0.84 per-mmHg/ng/kg/min [95% CI 0.74-0.95], p = 0.0062). Responsive patients had half the mortality hazard than resistant patients (HR: 0.50 [95% CI 0.32-0.78], p = 0.0026) and placebo patients (HR 0.58 [95% CI 0.40-0.86], p = 0.0064). Resistant patients had a similar mortality hazard to placebo (HR 1.17 [95% CI 0.80-1.72], p = 0.41). Compared to resistant patients, responsive patients had lower baseline renin and renin/angiotensin-II ratio, but a greater decrease in both at hr3. When stratified by baseline renin level, mortality was highest in placebo patients with high renin (69%) and angiotensin-II resistant patients with low renin (61%). CONCLUSIONS: Among patients with catecholamine-refractory vasodilatory shock treated with angiotensin-II, the AIMRITE was associated with mortality at day-28. Responsive angiotensin-II patients had higher survival versus both angiotensin-II resistant patients and those treated with placebo plus standard vasopressors. This index may serve as a prognostic indicator and early identifier of patients most likely to benefit from angiotensin-II.