Healthcare Utilization after Acute Kidney Injury in the Pediatric Intensive Care Unit

Abstract

Background and objectives: Little is known about the long-term burden of AKI in the pediatric intensive care unit. We aim to evaluate if pediatric AKI is associated with higher health service use post-hospital discharge.

Design, setting, participants, & measurements: This is a retrospective cohort study of children (≤18 years old) admitted to two tertiary centers in Montreal, Canada. Only the first admission per patient was included. AKI was defined in two ways: serum creatinine alone or serum creatinine and/or urine output. The outcomes were 30-day, 1-year, and 5-year hospitalizations, emergency room visits, and physician visits per person-time using provincial administrative data. Univariable and multivariable Poisson regression were used to evaluate AKI associations with outcomes.

Results: A total of 2041 children were included (56% male, mean admission age 6.5±5.8 years); 299 of 1575 (19%) developed AKI defined using serum creatinine alone, and when urine output was included in the AKI definition 355 of 1622 (22%) children developed AKI. AKI defined using serum creatinine alone and AKI defined using serum creatinine and urine output were both associated with higher 1- and 5-year hospitalization risk (AKI by serum creatinine alone adjusted relative risk, 1.42; 95% confidence interval, 1.12 to 1.82; and 1.80; 1.54 to 2.11, respectively [similar when urine output was included]) and higher 5-year physician visits (adjusted relative risk, 1.26; 95% confidence interval, 1.14 to 1.39). AKI was not associated with emergency room use after adjustments.

Conclusions: AKI is independently associated with higher hospitalizations and physician visits postdischarge.

Keywords: Acute Kidney Injury; Confidence Intervals; Emergency Service, Hospital; Epidemiology and outcomes; Intensive Care Units, Pediatric; Patient Discharge; Retrospective Studies; Risk; acute renal failure; children; clinical epidemiology; creatinine; hospitalization; pediatric nephrology; pediatrics.

Graphical abstract

Figure 1.

Study flow and selection criteria leading to the analysis population.

Figure 2.

Unadjusted and adjusted associations of AKI with 30-day, 1-year, and 5-year postdischarge hospitalizations. Relative risk (95% confidence interval) for 30-day, 1-year, and 5-year hospitalizations for patients with (A) AKI defined using serum creatinine alone (n=1575) and (B) AKI defined using serum creatinine and urine output (n=1622). The unadjusted (squares), model 1 adjustments (crosses), model 2 adjustments (triangles), and model 2 adjustments with effect modifiers (circles) relative risks and 95% confidence intervals for (A) AKI by serum creatinine criteria and (B) AKI by serum creatinine and urine output criteria, for 30-day, 1-year, and 5-year hospitalizations for patients. Multivariable Poisson regression was used in all multivariable analyses to calculate adjusted relative risks. Model 2 adjustments were not made for the 30-day outcomes due to low numbers of hospitalizations. Model 1 adjusted for age (continuous), sex, center, significant diagnoses from univariable analysis (oncologic, diabetes, trauma, infection, cardiac [nonsurgical], kidney, neurology/gastrointestinal/respiratory), death rate fourth quartile versus others, nephrotoxic antibiotics, vasopressors, and steroids. Model 2 adjusted for all variables in model 1 plus deprivation index (fourth/fifth quintile versus others), Pediatric Medical Complexity Algorithm score, rural versus urban, baseline number of hospitalizations, and family doctor/pediatrician (5 years only). Effect modifiers added to model 2 include: AKI×death rate, AKI×material deprivation index, AKI×social deprivation index, AKI×number of hospitalizations 12 months prior, and AKI×primary care doctor (yes/no). For model 2 the total N decreases because the deprivation index could not be calculated on all patients. n values for model 2: (A) AKI serum creatinine alone (n=1497), (B) AKI serum creatinine and urine output (n=1539). *P<0.05; **P<0.001.

Figure 3.

Unadjusted and adjusted associations of AKI with 30-day, 1-year, and 5-year postdischarge physician visits. Relative risk (95% confidence interval) for 30-day, 1-year, and 5-year physician visits for patients with (A) AKI defined using serum creatinine alone (n=1575) and (B) AKI defined using serum creatinine and urine output (n=1622). The unadjusted (squares), model 1 adjustments (crosses), model 2 adjustments (triangles), and model 2 adjustments with effect modifiers (circles) relative risks and 95% confidence intervals for (A) AKI by serum creatinine criteria and (B) AKI by serum creatinine and urine output criteria, for 30-day, 1-year, and 5-year physician visits for patients. Multivariable Poisson regression was used in all multivariable analyses to calculate adjusted relative risks. Model 1 and model 2 are the same as described in Figure 2 except we did not control for family physician/pediatrician for the 5-year outcome in model 2. Effect modifiers added to model 2 include: AKI×sex, AKI×center, AKI×oncologic, AKI×infection, AKI×cardiac (nonsurgical), AKI×kidney, AKI×neurology/gastrointestinal/respiratory, AKI×death rate, AKI×material deprivation index, AKI×Pediatric Medical Complexity Algorithm, and AKI×number of hospitalizations 12 months prior. For model 2 the total N decreases because the deprivation index could not be calculated on all patients. n values for model 2: (A) AKI serum creatinine alone (n=1497), (B) AKI serum creatinine and urine output (n=1539). **P<0.001.