Continuous measurements of GFR valuable for tracking perioperative changes in renal function

The pilot study, published in the International Journal of Nephrology, showed the feasibility of continuous GFR by measurements by continuous iohexol infusion in patients undergoing robot-assisted colorectal cancer surgery.

Previous studies have shown perioperative acute kidney injury (AKI) to be associated with considerable mortality and morbidity. Still, more needs to be done to prevent and treat this condition. This could be due to an inadequate understanding of renal pathology and a need for more tools for continuously monitoring overall kidney function in this setting. The best overall indicator of renal function is the measured GFR (mGFR); creatinine and cystatin C are more often used for GFR monitoring after surgery. Accurate determination of GFR is also critical for drug dosing, particularly for drugs with a narrow therapeutic window.

Iohexol's plasma clearance has been established as a reliable tool for GFR measurement in the steady-state condition. A recent study revealed that a continuous low-dose iohexol infusion could direct GFR changes in ICU patients at high AKI risk. Therefore, Lars M. Ytrebø, UiT – The Arctic University of Norway, Tromsø, Norway, and colleagues aimed to demonstrate that the method can also monitor GFR variations in patients without AKI risk factors undergoing robot-assisted colorectal cancer surgery during the first 72 hrs of the postoperative period.

The study included four patients undergoing robot-assisted colorectal cancer surgery from elective surgery listings. Postoperatively, GFR was determined by the single-sample iohexol clearance method and postoperatively at time intervals by a continuous iohexol infusion for 72 hrs.

Concurrent measurements of plasma concentrations of cystatin C and creatinine were done. GFR was calculated as (iohexol infusion rate (mg/min))/(plasma iohexol concentration (mg/mL)). The association of the three different filtration markers and GFR with time were analyzed. In all four patients, continuous infusion of iohexol was established and maintained throughout the study period without interference with ordinary postoperative care.

The researchers reported the following findings:

• Postoperative GFR at 2 hours were elevated compared to the preoperative measurements for patients 1, 2, and 3 but not for patient 4.
• Patients 1, 2, and 3 had u-shaped postoperative mGFR curves; patient 4 demonstrated a linear increase in mGFR with time.

"Continuous GFR monitoring over an extended period is feasible and can be utilized to investigate postoperative changes in renal function," the authors concluded.

They, however, acknowledged that continuous iohexol infusion is unlikely to become a clinically routine methodology. Still, it may become a valuable tool to evaluate renal function in patients at high risk of acute kidney injury.

Reference:

Kjellbjørn Jakobsen, Bjørn O. Eriksen, Ole M. Fuskevåg, Stephen J. Hodges, Lars M. Ytrebø, "Continuous Infusion of Iohexol to Monitor Perioperative Glomerular Filtration Rate", International Journal of Nephrology, vol. 2022, Article ID 8267829, 6 pages, 2022. https://doi.org/10.1155/2022/8267829