Defining human mean circulatory filling pressure in the Intensive Care Unit.

INTRODUCTION Potentially, mean circulatory filling pressure (Pmcf) could aid hemodynamic management in patients admitted to the intensive care unit (ICU). However, data regarding the normal range for Pmcf do not exist challenging its clinical use. We aimed to define the range for Pmcf for ICU patients and also calculated in what percentage of cases equilibrium between arterial blood pressure (ABP) and central venous pressure (CVP) was reached. In patients in which no equilibrium was reached, we corrected for arterial to venous compliance differences. Finally, we studied the influence of patient characteristics on Pmcf. We hypothesized fluid balance, the use of vasoactive medication, being on mechanical ventilation and the level of positive end-expiratory pressure would be positively associated with Pmcf. METHODS We retrospectively studied a cohort of 311 patients that had cardiac arrest in ICU whilst having active recording of ABP and CVP one minute after death. RESULTS Median Pmcf was 15 mmHg (IQR 12-18). ABP and CVP reached an equilibrium state in 52% of the cases. Correction for arterial to venous compliances differences resulted in a maximum alteration of 1.3 mmHg in Pmcf. Fluid balance over the last 24 hours, the use of vasoactive medication and being on mechanical ventilation were associated with a higher Pmcf. CONCLUSION Median Pmcf was 15 mmHg (IQR 12-18). When ABP remained higher than CVP, correction for arterial to venous compliance differences did not result in a clinically relevant alteration of Pmcf. Pmcf was affected by factors known to alter vasomotor tone and effective circulating blood volume.