Renal oxygenation measurement during partial nephrectomy using hyperspectral imaging may predict acute postoperative renal function

Abstract

Background and purpose: Digital Light Processing hyperspectral imaging (HsI) produces a highly sensitive, real-time tissue oxygenation map to monitor renal perfusion/oxygenation during partial nephrectomy (PN). Our initial experience with HsI revealed considerable variation in the baseline renal oxygenation, and we sought to correlate these differences with postoperative renal function.

Patients and methods: Hyperspectral images were collected intraoperatively in patients undergoing PN for cortical tumors. The kidney was illuminated with visible light (520-645 nm), the spectrum corresponding to that of oxyhemoglobin. Reflectance images were captured and digitally processed to determine the percentage of oxyhemoglobin (HbO2) at each image pixel. Images were taken before hilar occlusion; these %HbO2 values were used to categorize patients as high (>75% HbO2) or low (<75% HbO2) oxygenation, and postoperative eGFR was assessed.

Results: There were 26 patients who underwent PN with ice cooling and HsI imaging. Nineteen patients had a "low" preclamp oxygenation (mean 69%) while the other 7 had a "high" HbO2 (mean 77%). There was no difference in tumor size, hematocrit value, clamp time, or preoperative eGFR between the two groups. Patients with a higher baseline %HbO2 had no significant postoperative change in their eGFR (mean 0 mL/min/1.73 m(2), +4%), while those with the lower baseline %HbO2 had a significant acute decline (mean 15 mL/min/1.73 m(2), -20%, P=0.02, 0.006).

Conclusions: Baseline renal oxygenation, as measured with HsI, may help predict risk of postoperative renal insufficiency and may distinguish between patients with otherwise similar baseline characteristics, such as eGFR. HsI may provide individualized assessment of renal function to influence intraoperative decision-making to help preserve renal function.