Incidence of Acute Kidney Injury in Noncritical Pediatric Hospital Inpatients

Among critically ill pediatric hospital inpatients, studies have demonstrated a high rate of acute kidney injury (AKI), which is associated with increased mortality, increased length of stay, permanent loss of kidney function, and increased risk for chronic kidney disease (CKD). However, there are few data available on the incidence of AKI among hospitalized children, adolescents, and young adults not requiring intensive care.

Tracy L. McGregor, MD, and colleagues recently conducted a study designed examine the incidence of AKI as defined by Kidney Disease: Improving Global Outcomes (KDIGO) criteria among noncritically ill young patients. The researchers reported results of the retrospective observational cohort study in the American Journal of Kidney Diseases [2016;67(3):384-390].

The researchers utilized electronic medical records (EMRs) of 13,914 noncritical admissions to a tertiary-care children’s hospital during 2011 and 2012 to identify the incidence of AKI in noncritically ill children using KDIGO serum creatinine criteria with modification to allow ascertainment from clinically obtained EMR data. Exclusion criteria were age <28 days or >21 years and presence of CKD. Inclusion criteria included ≥2 serum creatinine measurements.

Of the 13,914 unique patients meeting inclusion and exclusion criteria, 17% (n=2374) had both a baseline and inpatient value to allow for AKI evaluation. Among the 11,540 patients not evaluated for AKI, 3704 had one serum creatinine measurement during hospitalization. Also included were 7836 (56% of all patients) patients who had no inpatient serum creatinine measurement; of those, 840 had a measurement in the 90 days prior to hospital admission.

There were some significant differences between those who were not evaluated for AKI and those who were in respect to race (74% and 77% white, respectively; P<.001) and ethnicity (9% and 7% Hispanic or Latino; P<.001). There were similarities in sex (55% and 54% male; P=.2). Those not evaluated for AKI were younger than those evaluated (median age, 5.8 vs 8.8 years; P<.001) and had shorter lengths of stay (median, 1 vs 3 days; P<.001).

Patients not evaluated for AKI also had fewer total unique medication exposures in the 24 hours before and initial 48 hours of admission (median, 2 vs 4 medications; P<.001). Finally, fewer patients not evaluated had nephrotoxic drug exposures (median, 0 vs 1; P<.001) compared with evaluated patients.

Of the 2374 patients who were evaluated for AKI, 30% (n=722; 5% of all eligible patients) met criteria for AKI. Compared with those who were evaluated but did not meet the AKI criteria (n=1652), those with AKI were younger (median age, 5.3 vs 10.5 years; P<.001); had lower weight for age (z score, –0.4 vs 0.0; P<.001), lower baseline serum creatinine (0.26 vs 0.42 mg/dL; P<.001), and higher maximum serum creatinine levels (0.53 vs 0.49 mg/dL; P<.001).

The numbers of total medication exposures per day and nephrotoxic medication exposures were similar in those with and without AKI (median, 4 vs 4; P=.004 and 1 vs 1; P=.05, respectively). Rates of contrast exposure were lower in patients with AKI (6% vs 10%; P=.002); median lengths of hospital stay were longer in those with AKI compared with those without AKI (4 vs 3 days; P<.001).

The definition of serum creatinine used in the study allowed for measurement of the nadir value before and after the peak serum creatinine measurement. The researchers conducted additional analyses of the 225 patients with AKI who had measured serum creatinine values before and after AKI to assess whether nadir serum creatinine measurements following AKI were systematically lower or higher. Results of that analysis demonstrated that minimal, if any, systematic increase or decrease occurred.

The study also included a close examination of clinical factors in the patients who met AKI criteria to categorize them by KDIGO stage. Of the 722 patients who met AKI criteria, 61% (n=443) met KDIGO criteria stage 1; 28% (n=199) met stage 2 criteria; and 11% (n=80) met stage 3 criteria. Those with stages 2 and 3 were younger (median age for stage 1, 6.4 years; stage 2, 4.1 years, and stage 3, 4.2 years; P<.001) and had longer hospital stays (4, 5, and 5 days, respectively; P<.001).

Proportions of patients exposed to group 1 nephrotoxic medications in the 24 hours before and 48 hours after admission were similar across AKI stages; however, proportions of patients exposed to group 2 nephrotoxic drugs increased across KDIGO stages (21%, 31%, and 34%, respectively; P<.001).Median tally of total unique medications per day was similar across AKI stages.

There were some limitations to the study cited by the authors, including the EMR data used for the study being derived from a single tertiary-care hospital and examined retrospectively; basing the definition of AKI on KDIGO criteria for changes in serum creatinine rather than including g urine output or estimation of glomerular filtration rate; and not requiring baseline values of serum creatinine to be measured before the elevated creatinine values indicating the AKI episode.

In their conclusion, the researchers said, “The ultimate goal of early detection and prevention of AKI requires more comprehensive screening of patients at risk and increased clinical recognition. In this cohort, even patients with previously described risk factors such as dehydration and nephrotoxic medication use were not universally screened. One strategy that has met success is the routine screening of children based on specific parameters around nephrotoxic medication use. Based on the data presented here, not only are these children at risk for AKI, but also those in a broader cohort that includes at least 5% of patients cared for in noncritical inpatient pediatric settings. Clinicians should have a lower threshold for screening their patients for AKI with serum creatinine measurement, especially in the setting of modifiable factors such as nephrotoxic medication, contrast exposure, and fluid management.”

Takeaway Points

  1. This study was conducted to assess the incidence of acute kidney injury (AKI) among children, adolescents, and young adults in a noncritical inpatient setting.
  2. Of 2374 patients evaluated, 30% (n=722) met Kidney Disease: Improving Global Outcomes criteria for AKI.
  3. At least 5% of all noncritical pediatric hospital inpatients without chronic kidney disease have an AKI episode during the routine hospital admission.