Dr. Silverton’s Research

Urine Oxygen: a Diagnostic and Therapeutic Tool for Hemorrhagic Shock

Perioperative acute kidney injury (AKI) is a concern for any anesthesiologist. While AKI increases morbidity and mortality, the problem is under-recognized because the diagnosis does not occur until 1-2 days post-surgery. This delay is because changes in serum creatinine take 24 – 48 hours to increase after injury has occurred. While the pathophysiology of AKI is multifactorial, surgical hemorrhage, anemia, and transfusion are likely significant contributors. A real-time monitor of end-organ oxygenation may result in earlier intervention, better end-organ perfusion, and decreased incidence of AKI. Multiple studies have proposed urinary oxygen concentration (PuO2) as a surrogate of kidney oxygenation. Preliminary data suggests that low PuO2 using a novel noninvasive monitor is associated with perioperative AKI and that simultaneous PuO2 and kidney tissue oxygen measurements are feasible in pigs. This trial seeks to investigate the following specific aims. Specific Aim 1: To establish noninvasive PuO2 as an early detection tool for kidney hypoxia during hemorrhage. Noninvasive PuO2 will be measured during controlled hemorrhage in pigs. During hemorrhage, it is hypothesized that changes in PuO2 will detect kidney hypoxia better than mean arterial pressure (MAP). Specific Aim 2: To determine whether a resuscitation protocol that includes PuO2 reduces kidney hypoxia compared to standard practice. After hemorrhage, pigs will be randomized to a resuscitation protocol driven by 1. MAP and urine output (UOP) or 2. MAP, UOP, and noninvasive PuO2. The hypothesis will be tested that the average kidney oxygen concentration will be higher in animals resuscitated using the PuO2 protocol compared to MAP and UOP alone. Furthermore, it is hypothesized that in this PuO2 group, there will be less kidney injury based on biomarkers and histology. Impact: By providing real-time data on critical end-organ oxygenation, the noninvasive device has the potential to reduce AKI and improve outcome.