Association between Urinary Potassium Excretion and Acute Kidney Injury in Critically Ill Patients

Abstract

A bstract Introduction Acute kidney injury (AKI) is defined in terms of serum creatinine (SrCrt) and urine output (UO). AKI occurs in 25% of critically ill patients, which increases the risk of morbidity and mortality. Early diagnosis of AKI is challenging, as utility of biomarkers is limited. This study is the first of its kind to estimate urinary potassium (UrK) excretion and its association with AKI in an Indian intensive care unit (ICU). Aims and objectives To study the association between UrK excretion and its ability to predict AKI in ICU patients. Material and methods During this prospective observational study, the patient's urinary indices and renal function tests were measured on day 1 of the ICU admission. UrK excretion and creatinine clearance (CrCl) were calculated from a 2-hour morning urine sample. Association between 2-hour UrK excretion and calculated CrCl and their ability to predict AKI in the subsequent 7 days was evaluated by Kidney Disease Improving Global Outcome (KDIGO)–AKI grading. Results Hundred patients admitted to ICU with a mean age of 53.59 ± 15.8 years were studied. The mean UrK excretion of 4.39 ± 2.52 was correlated linearly with CrCl and has a better prediction to AKI with the area under the receiver-operating characteristic curve value of 0.809 (CI 0.719–0.899), with a significant p -value ( p <0.05). UrK excretion value of 3.49 on day 1 of ICU admission had 87% sensitivity and 74% specificity in predicting AKI. Thirty-one (31%) developed AKI, of which seven (22.58%) required renal replacement therapy (RRT), with 19% of all-cause mortality. Conclusion Diagnosis of AKI with traditional methods is not promising. UrK excretion correlates well with CrCl, which can be considered as the simplest accessible marker for predicting AKI in ICUs. How to cite this article Kumar NS, Kumar GN, Misra KC, Rao M, Chitithoti S, Prakash SY . Association between Urinary Potassium Excretion and Acute Kidney Injury in Critically Ill Patients. Indian J Crit Care Med 2021;25(7):768–772.

Urine biochemistry assessment in the sequential evaluation of renal function: Time to think outside the box

“…Its major utility is to anticipate changes in sCr and is particularly helpful in patients with normal sCr. Urinary K + excretion is also helpful as it requires only urine sampling and is reliable even when obtained over a period of time as short as 2 h ( 36 , 37 ). However, it is possible that the early increases in FeK preclude an even earlier reduction in urinary K + excretion.…”

“…This phenomenon postpones the rise in serum K + (sK) as well as the decline in K + excretion during AKI development. Both FeK and urinary K + excretion have been proposed as useful parameters in renal function monitoring (33,(35)(36)(37)(38)(39). FeK is very different from urinary K + excretion: the former tends to elevate in AKI development while the latter tends to drop.…”

“…From this point of view, urinary K + excretion has the advantage of not being directly affected by sCr and is promptly available without blood sample collection. It must be obtained over a certain time period, which can be as short as 2 h ( 36 , 37 ). Although FeK calculation has the practical disadvantage of needing both serum and urinary sample collections, it is usually difficult to interpret urinary values uncoupled with their corresponding blood counterparts.…”

Low urinary sodium-to-potassium ratio in the early phase following single-unit cord blood transplantation is a predictive factor for poor non-relapse mortality in adults

“…On the other hand, urinary Na or K excretion and Na/K ratio have been reported to be associated with renal dysfunction and mortality in critically ill patients or those with cirrhosis 16 – 23 . Among critically ill patients, lower urinary Na excretion 17 , 21 and higher urinary K excretion 19 , 20 were associated with renal dysfunction and predicted progress of acute kidney injury. Moreover, lower urinary Na/K ratio was associated with renal dysfunction and mortality among patients with cirrhosis 22 , 23 .…”