What is Acute Kidney Injury (AKI)?

From the Guidelines

Acute Kidney Injury (AKI) should be diagnosed based on an increase in creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline (within prior 7 days) or urine volume 0.5 mL/kg/hr for 6 hours, as defined by recent studies 1. The diagnosis of AKI is crucial, as it affects up to 20% of hospital inpatients and between 30% to 60% of critically ill patients, with a significant impact on patient morbidity and mortality 1. AKI can be categorized as prerenal, renal, or postrenal, with prerenal and renal etiologies accounting for more than 97% of AKI cases 1. Key factors to consider in the diagnosis of AKI include:

• A thorough history and physical examination
• Laboratory analysis of blood and urine
• Measurement of serum creatinine and urine output
• Identification of the specific cause of AKI to guide treatment Some important points to note in the evaluation of AKI include:
• The need for renal replacement therapy (dialysis or hemofiltration) indicates stage 3 AKI, the highest stage
• Urine volume measurement is less important than measurement of serum creatinine in the diagnosis of AKI
• Renal biopsy may be indicated for differentiation of nephritic and nephrotic syndromes 1. Chronic Kidney Disease (CKD) is also an important consideration, defined as an abnormality of kidney structure or function, present for more than 3 months, with health consequences 1. CKD is common, affecting 10% of the world population, and is defined by five stages based on estimated Glomerular Filtration Rate (GFR) calculated using serum creatinine and standard equations 1. Evaluation of the patient with CKD will include a thorough history, physical examination, laboratory, and serologic workups, as well as markers of kidney damage such as measurement of albuminuria and urinary sediment 1.

From the Research

Definition and Causes of Acute Kidney Injury (AKI)

• Acute kidney injury (AKI) is defined as an increase in serum creatinine or a decrease in urine output over hours to days 2
• AKI can be categorized into prerenal, intrinsic renal, or postrenal causes, which can be determined through a thorough history and physical examination 2

Management and Treatment of AKI

• Fluid therapy is the cornerstone for the prevention and management of critically ill patients with AKI, but excessive fluid administration can negatively impact clinical outcomes 3, 4
• Diuretic therapy in AKI remains controversial, and its use is common despite a lack of evidence showing improved clinical outcomes 3
• Conservative management should be attempted first for patients with AKI, and renal replacement therapy or hemodialysis can be used if conservative management fails 5
• Fluid resuscitation should be individualized and take into account patient characteristics, nature of the acute illness, and risks and benefits of fluids 4

Prevention and Risk Factors of AKI

• Even one episode of AKI increases the risk of cardiovascular disease, chronic kidney disease, and death 2
• AKI appears to be related to increased rates of subsequent chronic kidney disease, and patients with AKI should be monitored closely 6
• Intravenous fluid use is beneficial for the prevention of contrast-induced AKI, while N-acetylcysteine use is not as well established 6

Fluid Management in AKI

• Buffered solutions are preferred for fluid resuscitation of patients at risk of AKI who do not have hypochloremia 4
• Albumin has a limited role, and starches should be avoided 4
• Fluids should only be administered until intravascular hypovolemia has been corrected and euvolemia has been achieved using the minimum amount of fluid required 4