Early prediction of acute kidney injury in neurocritical patients: relevance of renal resistance index and intrarenal venous Doppler as diagnostic tools

Abstract

Introduction: Implementing renal POCUS in critical care is a valuable tool complementing the physical examination of critical patients. As it is noninvasive, accessible, innocuous, and economical, it makes it possible to assess, at the bedside of patients, renal perfusion via ultrasound measurements such as the renal resistance index (RRI) and intrarenal venous Doppler (IRVD), which are considered early predictors of the acute renal lesion. Goals: Determine the relationship between the renal resistance index (RRI) and the degree of acute renal lesion according to KDIGO in neurocritical patients. Correlate the alterations to intrarenal venous Doppler (IRVD) flow with the degree of the acute renal lesion, according to KDIGO. Methods: An observational, analytical, prospective, longitudinal study was carried out in an ICU with an influx of neurocritical patients. Forty-three (43) patients participated. Their renal resistance index (RRI) and intrarenal venous Doppler (IRVD) were measured upon admission, 72 hours later, and 7 days after admission. Which of these tools better predicts acute renal lesions according to KDIGO was assessed. Results: In the study with 43 critical patients, no significant correlation was found between the RRI value and the acute renal lesion, according to KDIGO. On the contrary, a significant relation was found between intrarenal venous Doppler (IRVD) upon admission, 72 hours later, and 7 days after admission with the acute renal lesion according to KDIGO, with a value of r: 43=0.95 (P=0.54); 0.49 (P=0.001); 0.58 (P=0.000). When analyzing via the classification tree, it was determined that the variables better predicting the risk of suffering from an acute renal lesion before its occurrence are the measurement of intrarenal venous Doppler (IRVD) 7 days after admission and the value of the accumulated water balance. Conclusions: There is a positive and significant correlation between intrarenal venous Doppler (IRVD) and the acute renal lesion. Intrarenal venous Doppler (IRVD) and the accumulated water balance better predict the risk of suffering from an acute renal lesion in critical patients. In contrast, the renal resistance index (RRI) was unrelated to the acute renal lesion in the studied population