The Effects of Vasoactive Medications on Mean Circulatory Filling Pressure, Venous Resistance, Systemic Vascular Resistance, Cardiac Index, and Oxygen Extraction After Pediatric Heart Transplant: Leveraging High-Fidelity Physiologic Data

Background: The physiologic effects of vasoactive medications on the venous circulation remain incompletely understood. Contemporary bedside management often emphasizes the arterial circulation, whereas Guytonian physiology emphasizes the venous circulation and mean circulatory in determining steady-state cardiac output. The primary aim of this study was to characterize the effect of vasoactive medications on mean circulatory filling pressure and venous resistance. Methods: Demographic data and vasoactive data were collected from the electronic health record and collated with high-fidelity physiologic monitoring data. Mean circulatory filling pressure and venous resistance were calculated using clinically validated equations and then were modeled using a random forest regression incorporating postoperative time and infusion doses of epinephrine, norepinephrine, milrinone, vasopressin, phenylephrine, calcium, sodium nitroprusside, and nicardipine. Similar models were constructed for indexed systemic vascular resistance, cardiac index, cerebral oxygen extraction, and renal oxygen extraction. Results: Data from a total of 57 unique patients comprising 9,654,239 data points were analyzed. The model explained 91% of the variance in mean circulatory filling pressure and 58% of the variance in venous resistance. Vasopressin and norepinephrine were the most influential for mean circulatory filling pressure and venous resistance. Conclusion: Vasoactive medications modulate venous tone and impact mean circulatory filling pressure and venous resistance. High-fidelity physiologic data allow for characterizing these effects and guide titration of vasoactive medications at the bedside.