Comparison of Neutrophil Gelatinase-associated Lipocalin and Renal Resistive Index as Acute Kidney Injury Predictor in Critically Ill Patients at ICU H. Adam Malik Hospital Medan

BACKGROUND: Acute kidney injury (AKI) is a complication found in critically ill patients. Current consensus explains that diagnosis of AKI based on increased serum creatinine and decreased urine output. Neutrophil gelatinase-associated lipocalin (NGAL) level is increased a few hours after tubular damage occurred and can predict AKI more significantly than serum creatinine. Renal resistive index (RRI) is also a good marker in predicting the early stage of AKI. AIM: This study aimed to compare RRI and NGAL level as marker to predict incidence of AKI in critically ill patients treated in the Intensive Care Unit (ICU) at H. Adam Malik Hospital Medan. METHODS: This was an observational prospective cohort study and conducted in ICU at H. Adam Malik Hospital Medan in April-May 2021. This study had been approved by the Ethics Committee of Faculty of Medicine, Sumatera Utara University and H. Adam Malik Hospital Medan. Inclusion criteria are critical patients aged 18–65 years with 1st and 2nd priority level. Consecutive sampling was used. Resistive Index (RI) measured using USG Doppler by researcher and the results confirmed by ICU supervisors, while urine NGAL level measured within 3 h after ICU admission. Plasma urea and creatinine level measured after 24h after ICU admission. RESULTS: A total of 40 samples were collected; percentage of men and women are 66–35%, respectively (p = 0.001). There was a significant difference RI between AKI-group and non-AKI group (0.719 ± 0.060 and 0.060 ± 0.077, respectively) (p = 0.001). RI has a sensitivity of 71%, specificity of 84%, and accuracy of 87% in predicting occurrence of AKI with AUROC = 0.873. Meanwhile, NGAL has a sensitivity, specificity, and accuracy (66%, 89%, 78%, respectively) in early prediction of AKI incidence in critically ill patients. CONCLUSION: RI value was higher in AKI group than non-AKI group. RRI has better sensitivity than NGAL in predicting incidence of AKI.

Renal Resistive Index on Intensive Care Unit Admission Correlates with Tissue Hypoperfusion Indices and Predicts Clinical Outcome

Background: Recent advancements in the context of shock pathophysiology, support ultrasound assessment of organ perfusion. Renal resistive index (RRI) has been used to evaluate renal blood flow. Our aim was to investigate the relation between RRI, and global tissue hypoperfusion indices, in mechanically ventilated critically ill patients and their association with clinical outcome.Methods: In this prospective observational study, RRI was measured within 24 hours of intensive care unit (ICU) admission. Clinical and laboratory data, routine hemodynamic variables and gas exchange at the time of RRI assessment were recorded. The ratio of central venous-to-arterial carbon dioxide partial pressure difference by arterial-to-central venous oxygen content difference (P(cv-a)CO2/C(a-cv)O2) and lactate were used as global tissue hypoperfusion indices. Results A total of 126 mechanically ventilated patients were included [median age 61 (IQR 28) years, 74% males]. Seventy-seven patients had RRI values >0.7. P(cv-a)CO2/C(a-cv)O2 ratio and arterial lactate, were significantly higher in patients with RRI > 0.7 compared to those with RRI ≤0.7 [2.4 (2.2) versus 1.2 (0.6) and 2.88 (3.39) versus 0.62 (0.57) mmol/l respectively, both p<0.001)]. RRI was significantly correlated with P(cv-a)CO2/C(a-cv)O2 ratio and arterial lactate for the whole patient population (rho=0.64, both p<0.0001) as well as for the subset of patients with shock (rho=0.47, p=0.001; and r=0.64, p<0.0001 respectively).All-cause ICU mortality was 27.8%. Compared to survivors, ICU non-survivors had a higher RRI [0.80 (0.10) versus 0.70 (0.10), p<0.001] and higher P(cv-a)CO2 / C(a-cv)O2 ratio [3.67 (3.8) versus 0.91 (1.4)] and lactate levels [2.80 (2.00) versus 1.50 (1.20)], both p <0.001). Logistic regression models showed a significant association between RRI and P(cv-a)CO2/C(a-cv)O2 ratio with clinical outcome. RRI showed good ability to predict ICU mortality (AUC 74.9% (95% CI 61% - 88.8%). The combination of RRI with P(cv-a)CO2)/(C(a-cv)O2 ratio and lactate better predicted mortality than RRI alone [AUC 84.8% (95% CI 5.1% - 94.4%)] versus 0.74.9%, respectively, p<0.001).Conclusions: In mechanically ventilated patients, renal blood flow impairment, assessed by the RRI on ICU admission, correlates with global tissue hypoperfusion indices. In addition, RRI in combination with tissue perfusion estimation is more valuable in predicting clinical outcome than RRI alone.