Acute kidney injury (AKI; previously called acute renal failure) is the sudden loss of renal function necessary to maintain normal fluid and electrolyte balance and clear metabolic waste.1,2 AKI is typically manifested by an increase in serum creatinine, although the increase will not necessarily cause the creatinine to be outside the normal range. Use of serum creatinine alone to define AKI, however, is problematic because creatinine is an inaccurate estimate of glomerular filtration rate, it can be removed by dialysis, and variable cutoff values for creatinine have been used in AKI.3 Therefore, the international classification system, Kidney Disease: Improving Global Outcomes (Table 137-1), is preferred.4,5 The system uses creatinine and urine output criteria and can be applied to both children and adults, minimizing practice variation.2-4
TABLE 137-1KDIGO Classification of Renal Injury |Favorite Table|Download (.pdf) TABLE 137-1 KDIGO Classification of Renal Injury
|Stage* ||Lab Criteria ||Urine Output Criteria ||Other Criteria ||Neonatal Criteria |
|I ||Serum creatinine 1.5–1.9 times baseline or increase of ≥0.3 milligram/dL ||Urine output <0.5 mL/kg/h for 6 h || ||Creatinine as per children. Urine output <0.5 mL/kg/h for 6–12 h |
|II ||Serum creatinine 2–2.9 times baseline ||Urine output <0.5 mL/kg/h for 12 h || ||Creatinine as per children. Urine output <0.5 mL/kg/h for ≥12 h |
|III ||Serum creatinine 3 times baseline or increase in serum creatinine to ≥4 milligrams/dL ||Urine output <0.3 mL/kg/h for 24 h or anuria for ≥12 h ||Initiation or renal replacement therapy ||Serum creatinine >3 times baseline or ≥2.5 milligrams/dL. Urine output as for children |
In neonates, baseline creatinine is influenced by maternal creatinine and clearance is decreased in premature kidneys. Suggested modifications to the Kidney Disease: Improving Global Outcomes Classification for neonates are listed in Table 137-1.
AKI is common in critically ill children, with an incidence of 27% overall among children hospitalized for intensive care; 12% have severe AKI, and 1.5% require renal replacement therapy.6,7 Among children admitted to non–intensive care settings, the incidence is approximately 5%.8 While the incidence is highest among adolescents, it is also common in neonates, and more common in boys than girls.9 The most common causes of AKI in developed countries include cardiac and oncologic disease and their complications as well as nephrotoxin exposure, whereas sepsis, hypovolemia, and glomerulonephritis are common in the developing world.3,10-12 Regardless of etiology, AKI is consistently associated with morbidity and mortality among survivors, as well as long-term loss of renal function.3,12,13
AKI is the result of nephrotoxic and/or hypoxic injury to the glomeruli and renal tubules. Reduced blood flow causes hypoxic injury and damages the proximal tubular cells. Common nephrotoxins include aminoglycosides, contrast agents, calcineurin inhibitors, amphotericin B, NSAIDs, and cancer chemotherapeutics.14...