Macrovascular and Microvascular Response to Fluid Removal during Hemodialysis for Acute Kidney Injury

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Project Summary Over 13 million people develop acute kidney injury (AKI) each year. AKI increases the risk of incident chronic kidney disease, end-stage kidney disease, and death. Fluid removal (ultrafiltration) is an important component of managing dialysis-requiring AKI (AKI-D), but safe achievement of optimal volume status involves a delicate balance between preventing fluid overload and avoiding circulatory compromise. Acuity of illness and comorbid conditions render patients with AKI highly susceptible to even modest hemodynamic changes, and routine blood pressure monitoring may be inadequate to detect subtle, yet clinically meaningful, perfusion changes during hemodialysis. Continuous monitoring of systemic or local tissue perfusion is feasible using a variety of near-infrared optical technologies, but there has been limited application of these devices during hemodialysis particularly in the setting of AKI. The overarching premise of this proposal is that optimizing fluid management in an already vulnerable AKI population requires (1) a marker that captures an individualized hemodynamic response to fluid removal throughout hemodialysis treatments, and (2) more sensitive techniques to detect hypoperfusion. Funded by an F32 award, Dr. Wang previously leveraged continuous hematocrit monitoring (CHM) during maintenance hemodialysis treatments to calculate a semi-instantaneous plasma refill rate (PRR), which refers to the rate of refilling of the vascular space from the interstitial space during ultrafiltration. Through this K23 proposal, Dr. Wang will extend her investigations of PRR to the AKI setting and will evaluate novel approaches to assessing perfusion during hemodialysis. Specifically, Dr. Wang will perform mediation analysis using data from a large cohort of patients on maintenance hemodialysis to determine whether PRR mediates the effects of treatment-related factors on intradialytic hypotension (Aim 1); and, in a prospective cohort of patients with AKI-D, she will combine continuous hematocrit monitoring with two noninvasive techniques – diffuse correlation spectroscopy and diffuse optic spectroscopy ‒ to simultaneously measure changes in systemic perfusion (Aim 2) and cerebral perfusion and oxygenation (Aim 3) as a novel approach to elucidate the physiology underlying both overt and subtle hemodynamic effects of hemodialysis. Additionally, she will use bedside testing to link spatiotemporal changes in tissue physiology with changes in cognitive function. To conduct this work, Dr. Wang will utilize the formal methodologic training and practical experience in epidemiology, study design, and longitudinal analysis that she acquired through the Master of Science in Clinical Epidemiology Program. Through her K23 career development plan, she will gain (1) skills in designing and implementing prospective studies in dialysis, (2) experience studying outcomes in acute care, and (3) expertise in advanced methods for analyzing multidimensional data. Upon completion of this work, Dr. Wang will be well-positioned to obtain R01 funding to continue working toward her long-term goal of developing novel approaches that will increase the precision of renal replacement therapy and improve patient outcomes.