The impact of blood pressure targets on haemodynamics in patients with cardiogenic shock caused by infarction-related out-of-hospital cardiac arrest: a substudy of the BOX-trial

BACKGROUND: Noradrenaline is frequently used to increase mean arterial pressure (MAP) in patients with cardiogenic shock caused by infarction-related out-of-hospital cardiac arrest (OHCA-AMICS). This Blood pressure and Oxygenation-Targets after OHCA (BOX)-trial subanalysis investigates the impact of different noradrenaline-mediated MAP-targets on overall hemodynamics and outcomes in OHCA-AMICS patients. METHODS: The BOX-trial compared randomized, double-blinded MAP-targets of 63 mmHg (low-target) and 77 mmHg (high-target) in comatose OHCA patients. For this subanalysis, patients meeting eligibility criteria for AMICS according to the ongoing NORshock trial were included (percutaneous coronary intervention, hypotension, signs of hypoperfusion and <30 minutes to ROSC). Hemodynamic parameters assessed were cardiac index (CI) and pulmonary capillary wedge pressure (PCWP). Markers of tissue perfusion comprised SvO₂ and lactate. Clinical endpoints included 365-day mortality, renal replacement therapy (RRT) and neurological outcomes. RESULTS: Within the cohort of 258 patients (Low-target n = 132, High-target n = 126), mean age was 63 (±11) years, 84% were male, and patient characteristics were well balanced between groups. The high-target group received significantly higher doses of noradrenaline. CI increased over time in both groups (Low-target: 1.50→2.88; High-target: 1.77→2.92 L/min/m²). Despite 8-19% higher CIs during the first 24 hours, the high-target group consistently exhibited higher PCWPs. SvO2 was higher in the high-target group. Lactate levels were comparable and on average normalized in both groups within 6 hours. Mortality, need for RRT and neurological outcomes did not differ significantly. CONCLUSION: In OHCA-AMICS patients, higher noradrenaline-mediated MAP increased CI and SvO2 but did not enhance tissue perfusion or clinical outcomes, and were associated with higher left-sided filling pressures.