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Kidney Week

Abstract: PO0180

Urinary Oxygen Partial Pressure to Monitor AKI Risk

Session Information

Category: Acute Kidney Injury

  • 101 AKI: Epidemiology, Risk Factors, and Prevention


  • Lofgren, Lars, University of Utah Health, Salt Lake City, Utah, United States
  • Kuck, Kai, University of Utah Health, Salt Lake City, Utah, United States
  • Silverton, Natalie, University of Utah Health, Salt Lake City, Utah, United States

In a prior study, we showed that patients who developed acute kidney injury (AKI) had lower mean urinary oxygen partial pressure (PuO2) following cardiopulmonary bypass (CPB). However, PuO2 is unreliable when urine flow is low and little is known about the distribution of urine flow intraoperatively. The objective of this research was to determine the distribution of the length of sections of unreliable PuO2 data due to low flow.


Following IRB approval and informed consent, a device that measures PuO2 and urine flow was placed in cardiothoracic surgery patients. PuO2 and urine flow (sampled at 1 Hz) were deemed not reliable when urine flow was below a threshold. Patients who did not meet a percent valid data threshold were excluded. Mean PuO2 following CPB and the maximum and median length of sections of invalid data were calculated. Data were generated for a percent valid data threshold of 30 % and urine flow rate thresholds of 0.1 to 1 mL/kg/hr at 0.1 increments. Patients who met the KDIGO criteria for AKI were compared to non-AKI patients. In addition, patients with Stage 2 or 3 AKI based on the KDIGO serum creatinine criteria were assigned to the Severe AKI group and were compared to patients with stage 1 or no AKI. The area under the curve (AUC) of a receiver-operator (ROC) plot of mean PuO2 estimating AKI development was calculated for each comparison.


AUC was 0.69 for AKI when the flow threshold was 0.4 ml/kg/hr. The average for all patients of the median and maximum length of invalid data was 37 seconds and 387 seconds, respectively. For Severe AKI, the AUC was 0.81 for a flow threshold of 0.7 ml/kg/hr. As the maximum length of invalid data sections increases the AUC decreases.


Sections of unreliable PuO2 data are sufficiently short and do not significantly impact the performance of PuO2 as a marker of AKI when a urine flow threshold is used to filter the data. The data demonstrate the feasibility of measuring PuO2 to monitor AKI risk during cardiothoracic surgery. Further research is needed to determine if intraoperative PuO2 can reduce the incidence of AKI.

AUC of mean PuO2 and distribution of length of invalid data sections