What is Acute Kidney Injury (AKI)?

From the Guidelines

Acute Kidney Injury (AKI) should be diagnosed and staged according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria, which defines AKI as an increase in creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline within 7 days, or urine volume less than 0.5 mL/kg/hr for 6 hours 1.

Diagnosis and Staging of AKI

The diagnosis of AKI is based on the KDIGO criteria, which includes an increase in creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline within 7 days, or urine volume less than 0.5 mL/kg/hr for 6 hours. The staging of AKI is carried out retrospectively when the episode is complete, and patients are classified according to the highest possible stage where the criterion is met, either by creatinine rise or by urine output.

Management of AKI

Management of AKI focuses on identifying and treating the underlying cause, maintaining fluid and electrolyte balance, and preventing further kidney damage. For volume depletion, intravenous fluids (typically isotonic crystalloids like normal saline at 10-20 mL/kg) should be administered. Nephrotoxic medications such as NSAIDs, aminoglycosides, and certain contrast agents should be discontinued or dose-adjusted. Electrolyte abnormalities, particularly hyperkalemia, require prompt treatment with calcium gluconate (10 mL of 10% solution IV), insulin (10 units regular insulin with 50 mL of 50% dextrose), and sodium bicarbonate (50 mEq IV) for severe cases.

Prevention Strategies

Prevention strategies include maintaining adequate hydration, especially before contrast procedures (with pre-hydration using isotonic saline at 1 mL/kg/hr for 6-12 hours before and after contrast), avoiding nephrotoxic medication combinations, and dose-adjusting medications for patients with pre-existing kidney disease. Renal replacement therapy (dialysis) should be considered for refractory hyperkalemia, volume overload, severe metabolic acidosis, or uremic symptoms. Some key points to consider in the management of AKI include:

• Identifying and treating the underlying cause of AKI
• Maintaining fluid and electrolyte balance
• Preventing further kidney damage
• Discontinuing or dose-adjusting nephrotoxic medications
• Promptly treating electrolyte abnormalities, particularly hyperkalemia
• Considering renal replacement therapy for severe cases The KDIGO criteria provide a standardized approach to the diagnosis and staging of AKI, and management should be tailored to the individual patient's needs and underlying cause of AKI, as supported by the study 1.

From the Research

Definition and Diagnosis of AKI

• Acute kidney injury (AKI) is characterized by an abrupt decrease in renal function or the onset of frank renal failure 2.
• AKI is defined as an increase in serum creatinine or a decrease in urine output over hours to days 3.
• The Kidney Disease: Improving Global Outcomes (KDIGO) defines AKI as an increase in the serum creatinine (SCr) level of 0.3 mg/dL or more within 48 hours, an SCr level increase of 1.5 times or more of the baseline level within 7 days, or a decrease in urine output to less than 0.5 mL/kg/hour for 6 hours 2.

Causes and Risk Factors of AKI

• AKI typically is caused by systemic illness or toxic exposure 2.
• Determining the cause is critical when possible, and the history should focus on risk factors, including nephrotoxic drugs 2.
• A thorough history and physical examination can help categorize the underlying cause as prerenal, intrinsic renal, or postrenal 3.

Management and Treatment of AKI

• AKI management includes control of the underlying cause, achievement and maintenance of euvolemia, nutritional optimization, blood glucose control, and pharmacotherapy 2.
• Treatment with fluid resuscitation or diuresis is guided by the volume status 2.
• Diuretics are a common intervention in critically ill patients with AKI, with furosemide being the most commonly used 4.
• Continuous infusion of furosemide seems to be effective in promoting diuresis and decreasing the need for renal replacement therapy (RRT) 5.

Referral and Follow-up

• Emergent referral to a nephrology subspecialist is recommended for patients with stage 2 or 3 AKI; patients with stage 1 AKI and a concomitant, decompensated condition; or if the etiology of the AKI is unclear 2.
• Urgent referral should be considered if the injury does not improve with treatment or if glomerulonephritis is suspected 2.
• Early determination of etiology, management, and long-term follow-up of AKI are essential, as even one episode of AKI increases the risk of cardiovascular disease, chronic kidney disease, and death 3.