Measurement of Cerebral Status under Non-Chronic Hemodynamic Conditions

Blood flow is a critical physiological function. Despite its importance it is almost never assessed as actual flow, but rather by a surrogate, most typically blood pressure assessed using an arm or wrist cuff. More sophisticated methods of acquiring blood flow information include imaging using ultrasound pulse-wave or color flow. However, they mostly provide flow velocity instead of blood flow in milliliters per minute. Mean velocities can be used to estimate actual flow, but these calculations are based on often invalid assumptions. We have shown previously that 3D color flow can yield actual volumetric blood flow without any assumptions (3DVF). Here we employ an acute preclinical injury model that simulates severe traumatic brain injury. Specifically in a Yorkshire mix pig model, we simulate brain trauma by the placement and inflation of a subdural balloon catheter. We also simulate an associated traumatic abdominal injury with massive blood loss, hemorrhage, of 40 to 50%. Actual blood flow is obtained by an invasive flowmeter. Blood gases, intracranial pressure and blood flow were acquired among other parameters. During normal physiology (baseline), the mean oxygen extraction ratio obtained in the jugular vein was 40.6%±13.0%. Hemorrhagic shock caused an increase to a peak of 68.4%±15.6%. Blood flow was acquired with an average bias of -9.6% (-14.3% root mean squared error). The flowmeter itself showed a median error of -11.5% to 39.7%. Phases of flow reversal did not negatively impact 3DVF flow estimation.