Matthew Luchette
Boston Children's Hospital
Boston, Massachusetts
Disclosure information not submitted.
Kerri LaRovere, MD
Assistant Professor of Neurology
Boston Children's Hospital, United States
Disclosure information not submitted.
Robert Tasker, MA, MD, MBBS, FRCP
Senior Associate Staff Physician
Boston Children's Hospital
Milton, Massachusetts
Disclosure information not submitted.
Alireza Akhondi-Asl, PhD
Instructor in Anaesthesia
Boston Children's Hospital, United States
Disclosure information not submitted.
Title: Cerebral Perfusion Requires Elevated Mean Arterial Pressure with in silico Model of Sepsis
Introduction: Ensuring optimal perfusion to end organs is a principal management component of the patient with septic shock. In this state, systemic vascular resistance (SVR) is lowered, resulting in a decreased mean arterial pressure (MAP), which causes a compensatory increase in cardiac output (CO). While adult studies suggest that targeting a MAP greater than the 5th-percentile may be sufficient for end organ perfusion, similar consensus is lacking in the pediatric literature. Furthermore, the lower bound for MAP at which cerebral autoregulation is maintained remains unknown. We performed an in silico simulation of blood flow through the Circle of Willis to assess the optimal MAP threshold for maintaining cerebral perfusion.
Methods: We created a coupled model of cerebral autoregulation incorporating a one-dimensional model of the primary branches of the cerebral arteries and a zero-dimensional model of resistance control. We modeled flow and pressure in the left and right Middle Cerebral Artery (MCA) in two patient states: the baseline state, in which SVR was 100%, CO was maintained at 5.6 L/min, and MAP maintained at 103 mmHg (adult 95th-percentile); and the septic shock state, in which SVR was 35%, CO was maintained at 9.0 L/min and MAP maintained at 64 mmHg (adult 5th-percentile).
Results: The average pressure in each MCA for the baseline state was 93.14 mmHg, with an average flow of 102.6 mL/min. For the simulated patient with septic shock, the average MCA pressure decreased to 55 mmHg, with a corresponding decrease in flow to 77.4 mL/min. Increasing the cardiac output to 12.4 L/min, with a corresponding increase in MAP to 86.5 mmHg, the 50th-percentile, results in MCA blood flow similar to the baseline non-septic state.
Conclusions: Using an in silico model of the Circle of Willis, we show that MCA blood flow is decreased in septic shock when the 5th-percentile of blood pressure is accepted, suggesting that cerebral autoregulation is unable to compensate for this degree of hypotension. Blood flow returns to baseline, however, when cardiac output increases with generation of the 50th-percentile of blood pressure. Future clinical studies should investigate the consequence and differences in tolerating the 5th- as opposed to the 50th-percentile in blood pressure on cerebral blood flow.