Investigating the Relationship Between Age-Adjusted Shock Index and AKI in Children Admitted to the Pediatric Intensive Care Unit

Abstract

Background: Acute kidney injury (AKI) is a serious complication in critically ill children admitted to pediatric intensive care units (PICUs) and is associated with increased morbidity and mortality. However, early identification of patients at risk for AKI remains a clinical challenge. Objectives: This study aimed to investigate the association between the age-adjusted shock index (SI) and the development of AKI in critically ill children admitted to the PICU. Methods: This prospective cohort study was conducted in the PICU at Amir Kabir Hospital, Arak, Iran, from February to July 2023. A total of 80 children aged 1 month to 18 years with a PICU stay ≥ 24 hours were enrolled. The shock index was calculated as heart rate divided by systolic blood pressure and categorized using age-adjusted thresholds. Acute kidney injury was diagnosed according to KDIGO criteria, based on changes in serum creatinine and urine output within 48 hours of admission. Independent t tests, Mann-Whitney U tests, chi-square tests, and logistic regression were used to analyze the data using STATA version 12. Results: The mean age of the participants was 7.21 ± 4.76 years, and 46.3% were male. The overall prevalence of AKI was 90% (n = 72; 95% CI, 81.0 - 95.0% using the Wilson method; 95% CI, 81.4 - 94.8% using the exact binomial method). Patients with elevated SI had significantly lower urine output (0.33 ± 0.11 vs 0.63 ± 0.04 mL/kg/h; P = 0.038) and a lower glomerular filtration rate (GFR) at 24 hours (62.86 ± 20.88 vs 88.29 ± 19.9 mL/min/1.73m2; P = 0.002) than those with normal SI. Elevated SI was present in 90.3% of patients with AKI versus 50% of patients without AKI. Logistic regression showed that patients with elevated SI had 9.28-fold higher odds of developing AKI (95% CI, 1.34 - 59.98; P = 0.001) and 8-fold higher odds of GFR reduction (95% CI, 1.18 - 50.47; P = 0.003). Conclusions: An elevated age-adjusted shock index was significantly associated with AKI development and reduced kidney function in critically ill children admitted to the PICU. Routine monitoring of this simple, noninvasive parameter may facilitate the early identification of high-risk patients and guide preventive interventions.