European Journal of Cardiovascular Medicine

Acute kidney injury (AKI) represents a sudden decline in renal function, characterised by the impaired elimination of metabolic waste products3 . In children, AKI is a significant cause of morbidity and mortality, particularly in the intensive care setting20 . Over the past decade, there has been considerable progress in understanding AKI in paediatric patients, addressing previous limitations in data and methodological consistency21 . The development and refinement of standardised definitions for AKI, such as the Risk, Injury, Failure, Loss, End-stage renal disease (RIFLE) criteria and its paediatric adaptation (pRIFLE), as well as the Acute Kidney Injury Network (AKIN) and Kidney Disease Improving Global Outcomes (KDIGO) classifications, have facilitated more consistent epidemiological reporting2 ....

However, the incidence, aetiology, and outcomes of AKI in children can vary significantly between developed and developing countries, and even within a single country based on the hospital and its resources2 . The majority of existing data on paediatric AKI originates from Western nations, and there is a relative paucity of information from our country2 . Understanding the specific diseases and conditions leading to AKI in our local paediatric population is crucial for early identification, prevention, and targeted treatment strategies2 . This study aimed to investigate the incidence, risk factors, and outcome of AKI among children aged 1 to 12 years admitted to the intensive care unit of a tertiary care hospital in Guntur, Andhra Pradesh, India3.

Aim and Objectives

The primary aim of this study was to determine the incidence, risk factors, and outcome of acute kidney injury in children between 1 year and 12 years of age admitted to the intensive care unit in a tertiary care hospital³ .

The specific objectives were:

• To determine the incidence of AKI in children admitted to the PICU.
• To identify the risk factors associated with the development of AKI in this population.
• To assess the outcomes of AKI, including mortality, length of PICU stay, need for mechanical ventilation and dialysis, and recovery rates.

Study Design and Setting: This was a prospective and observational study conducted in the Department of Paediatrics at Guntur Medical College (GGH), Guntur, a tertiary care hospital in Andhra Pradesh, India⁴ .

Study Duration and Participants: The study was conducted over a period of 21 months, from October 2022 to June 20244 . The study population comprised children aged between 1 year and 12 years who were admitted to the PICU during the study period⁴ . A convenience sampling technique was employed to recruit more than 1000 participants⁴ .

Inclusion and Exclusion Criteria: Children aged between 1 and 12 years admitted to the PICU were included in the study⁴ . Children with pre-existing kidney disease and those whose parents or guardians did not provide informed consent were excluded⁶ .

Data Collection: After obtaining informed consent from the parent or guardian6 ..., patient demographic data, medical history, and clinical details were collected using a pre-structured case pro forma (Annexures⁾⁶ .... A thorough clinical examination was performed, and essential routine investigations, including serum creatinine and urine output, were recorded6 ....

Definition and Classification of AKI: Patients were classified as AKI cases based on the RIFLE criteria6 .... The RIFLE criteria categorises AKI into three stages of severity: Risk, Injury, and Failure, based on changes in serum creatinine or urine output²⁵ . Regardless of the stage based on these criteria, patients requiring renal replacement therapy (RRT) were classified as having reached the Failure stage²⁵ .

Data Analysis: The collected data were analysed using the statistical package for the social sciences (SPSS 20) version 20.0 and Microsoft Excel5 . Descriptive statistics were used to summarise the data, and appropriate statistical tests (Chi-Square test, Fisher’s Exact test, t-tests) were employed to assess associations between variables and the incidence and outcomes of AKI. A p-value of less than 0.05 was considered statistically significant9 .... Multivariate logistic regression analysis was performed to identify independent risk factors for the development of AKI²² .

Ethical Considerations: The study was approved by the Institutional Ethical Committee of Guntur Medical College²⁶ . Informed consent was obtained from the parents or guardians of all participating children after explaining the study's objectives, procedures, potential risks, and benefits in their own language7 .... Confidentiality of patient data was maintained throughout the study⁷ .

Incidence of AKI: Out of the 1159 children admitted to the PICU during the study period, 198 (17.1%) developed AKI8 . The remaining 961 (82.9%) did not develop AKI⁸ .

AKI Stage based on RIFLE Criteria: Among the 198 patients who developed AKI, 125 (63.1%) were classified as Risk, 53 (26.8%) as Injury, and 20 (10.1%) as Failure based on the RIFLE criteria²⁸ .

Association of Age and Gender with AKI: The incidence of AKI varied across different age groups, with the highest incidence of 33.8% observed in the 6-10 years age group9 . This association was statistically significant (p=0.04)9 . There was no statistically significant association between gender and the incidence of AKI [Table 5].

Duration of PICU Stay and AKI: The study found a statistically significant association between the duration of stay in the PICU and the incidence of AKI [Table 6, 44].

Serum Creatinine and Creatinine Clearance: Minimum and maximum serum creatinine levels were significantly different between patients with and without AKI (p<0.001)10 .... AKI patients had significantly higher serum creatinine levels11 .... Similarly, minimum and maximum creatinine clearance rates were significantly lower in patients who developed AKI (p<0.001)¹²

Mortality and AKI: The mortality rate was significantly higher in the AKI group (18.2%) compared to the non-AKI group (2.7%) (p<0.001)¹³

Mechanical Ventilation and AKI: A significantly higher proportion of AKI patients (18.7%) required mechanical ventilation compared to non-AKI patients (6.7%) (p<0.001)14 . The duration of ventilation was also significantly longer in the AKI group (p<0.001)¹⁵ .

Dialysis and AKI: Six (3.0%) patients in the AKI group required dialysis16 .

Causes of AKI: The most common cause of AKI identified in this study was pre-renal aetiology (70.7%), followed by intrinsic (15.2%) and post-renal (4.0%) causes [Table 17]. Sepsis was noted as a significant cause in 6.1% of AKI cases [Table 17, 40].

Recovery from AKI: Complete recovery was observed in 159 (80.3%) of the 198 patients who developed AKI¹⁷ ....

Risk Factors for AKI: Multivariate logistic regression analysis revealed that hypotension, use of nephrotoxic drugs, sepsis, and the need for ventilation were independent risk factors for the development of AKI

(p<0.001)¹⁶ ....

Association between Creatinine and Urine Output Staging: A significant correlation was found between creatinine criteria staging and urine output staging among AKI patients³⁷

This study provides valuable insights into the incidence, risk factors, and outcomes of AKI in a cohort of critically ill children in a tertiary care hospital in South India. The incidence of AKI (17.1%) is comparable to findings from other studies in paediatric intensive care units37 ..., although variations exist depending on the definition used and the patient population studied²³ .... The higher incidence of AKI in the 6-10 years age group could be attributed to the spectrum of illnesses prevalent in this age range requiring PICU admission⁹ .

The significant association between prolonged PICU stay and AKI highlights the potential for AKI to develop during critical illness and the impact of AKI on the duration of hospitalisation²⁹ . The study's findings strongly support the role of elevated serum creatinine and reduced creatinine clearance as key indicators of AKI, consistent with other research²⁹ ....

The significantly higher mortality rate in children with AKI underscores the severity of this complication in critically ill patients¹³ .... This is in line with previous studies that have identified AKI as an independent risk factor for mortality in the PICU20 . The increased need for and duration of mechanical ventilation in AKI patients likely reflects the overall severity of illness and the complex interplay between organ systems¹⁴ .... The finding that pre-renal causes were the most common aetiology suggests that factors leading to reduced renal perfusion are prevalent in this setting³⁴ .

The identified independent risk factors for AKI – hypotension, nephrotoxic drug use, sepsis, and ventilation – are well-established in the literature¹⁶ .... These factors often coexist in critically ill children and contribute to the pathogenesis of AKI through various mechanisms, including haemodynamic instability, direct tubular injury, and inflammatory responses⁴⁵ .... The significant correlation between creatinine and urine output staging reinforces the importance of monitoring both these parameters for early detection and assessment of AKI severity³⁷ ....

The relatively high rate of complete recovery (80.3%) in AKI survivors suggests that with timely and appropriate management, renal function can often be restored in children with AKI¹⁷ .... However, the significant proportion who did not recover highlights the potential for long-term renal sequelae and the need for follow-up studies¹⁵ ....

Limitations: This study was conducted in a single tertiary care centre, which may limit the generalisability of the findings to other settings. The use of convenience sampling might have introduced some selection bias. While the RIFLE criteria were used for AKI classification, other definitions like KDIGO and AKIN also exist and might yield slightly different incidence rates²³

This study demonstrates that AKI is a common and serious complication in children aged 1 to 12 years admitted to the PICU of this tertiary care hospital. The identified incidence, risk factors, and adverse outcomes, particularly increased mortality and prolonged resource utilisation, underscore the clinical significance of AKI in this vulnerable population¹⁸ . Early detection using standardised criteria like RIFLE, meticulous attention to modifiable risk factors such as hypotension and nephrotoxic drug exposure, aggressive management of sepsis, and judicious use of mechanical ventilation are crucial strategies for preventing the development and progression of AKI and ultimately improving patient outcomes19 .... Further research, including multi-centre studies, is warranted to validate these findings and develop evidence-based guidelines for the prevention and management of paediatric AKI in our region.

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