Impact of Blood Pressure Targets on Central Hemodynamics during intensive care after Out-of-Hospital Cardiac Arrest

OBJECTIVES: The aim was to investigate the advanced hemodynamic effects of the two MAP-targets during intensive care on systemic hemodynamics in comatose patients after cardiac arrest Design: Secondary analysis of a randomized controlled trial.

SETTING: Primary vasopressor used was per protocol norepinephrine. Hemodynamic monitoring was done with pulmonary artery catheters (PAC) and measurements were made on predefined time points. The primary endpoint of this substudy was the difference in cardiac index within 48h from a repeated measurements-mixed model. Secondary endpoints included systemic vascular resistance index (SVRI), heart rate, and stroke volume index.

PATIENTS: Comatose survivors after out-of-hospital cardiac arrest.

INTERVENTIONS: The "Blood pressure and oxygenations targets after out-of-hospital cardiac arrest (BOX)"-trial was a randomized, controlled, double-blinded, multicenter-study comparing targeted mean arterial pressure (MAP) of 63 mmHg (MAP63) vs 77 mmHg (MAP77).

MEASUREMENTS AND MAIN RESULTS: Among 789 randomized patients, 730 (93%) patients were included in the hemodynamic substudy. From PAC-insertion (median 1 hours after ICU-admission) and the next 48 hours, the MAP77-group received significantly higher doses of norepinephrine (mean difference 0.09 µg/kg/min, 95% confidence interval (CI) 0.07-0.11, pgroup<0.0001). Cardiac index was significantly increased (0.20 L/min/m2 (CI 0.12 - 0.28), pgroup<0.0001) as was SVRI with an overall difference of (43 dynes m2/s/cm5 (CI 7-79); Pgroup=0.02). Heart rate was increased in the MAP77-group (4 beats/minute; CI 2-6, pgroup<0.003), but stroke volume index was not (pgroup=0.10).

CONCLUSIONS: Targeted MAP at 77 mmHg compared to 63 mmHg resulted in a higher dose of norepinephrine, increased cardiac index and SVRI. Heart rate was also increased, but stroke volume index was not affected by a higher blood pressure target.