The impact of blood pressure targets on venous return physiology during post cardiac arrest care

Abstract

Background: Venous return (VR) physiology may be elucidated using a calculated mean systemic filling pressure analogue (Pmsa) that reflects the stressed intravascular volume. The aim of this study was to explore differences in VR physiological variables with the hypothesis that vasopressor therapy targeting a higher mean arterial pressure (MAP) would associate with an increased volume state. This would be important to appreciate the intravascular volume effect of an intervention that traditionally is judged by the pressure response alone. Methods: This exploratory study used data from the BOX trial that investigated a higher (MAP of 77 mmHg, MAP77) versus a lower (63 mmHg, MAP63) blood pressure target during intensive care of survivors from out-of-hospital cardiac arrest. Data from 730 patients (MAP63, n = 362 and MAP77, n = 368) were used to calculate Pmsa, the driving pressure for VR (VRdP, the difference between Pmsa and central venous pressure [CVP]), the resistance to venous return (RVR, the VRdP divided by the cardiac output [CO]) and heart efficiency (Eh, the VRdP divided by Pmsa). Linear mixed models were used to evaluate longitudinal haemodynamic data captured from admission to the intensive care unit and over 36 h. Results: The Pmsa was consistently higher in the MAP77 group (p