Acute Kidney Injury Management

Definition and Diagnosis

Acute kidney injury (AKI) is defined as a rise in serum creatinine of ≥26 μmol/l (0.3 mg/dl) within 48 hours, or a 50% or greater increase in serum creatinine from baseline within 7 days, or a reduction in urine output to less than 0.5 ml/kg/h for more than 6 hours, according to the Kidney Disease Improving Global Outcomes (KDIGO) guideline 1
The KDIGO Classification (2012) is the most widely accepted definition, combining elements of RIFLE and AKIN, as stated by the Kidney Disease Improving Global Outcomes (KDIGO) 1

Diagnose acute renal failure using KDIGO criteria:

Stage	Serum Creatinine Criterion	Urine Output Criterion
1	Increase ≥0.3 mg/dL within 48h or 1.5-1.9 times baseline	<0.5 mL/kg/h for 6-12h
2	2.0-2.9 times baseline	<0.5 mL/kg/h for ≥12h
3	≥3.0 times baseline or ≥4.0 mg/dL or RRT initiation	<0.3 mL/kg/h for ≥24h or anuria for ≥12h	[2]

Clinical features of AKI include history of volume depletion, hypotension or signs of decreased effective circulating volume, and response to fluid resuscitation, often occurring in patients with cirrhosis, heart failure, or sepsis 3
Laboratory findings for AKI include urine sodium >40 mEq/L, FENa >2%, urine osmolality <350 mOsm/kg, abnormal urine sediment, and elevated urinary biomarkers like NGAL 3

Renal ultrasound is the first-line imaging modality for all AKI cases, evaluating kidney size, echogenicity, and hydronephrosis, with normal kidney size suggesting AKI rather than CKD 4
Color Doppler ultrasound assesses renal perfusion, evaluates for renal vein thrombosis, and confirms presence/absence of ureteral jets in bladder 4
CT scan is used when ultrasound is inconclusive, better for identifying obstruction cause, with unenhanced CT preferred to avoid contrast nephrotoxicity 4
Monitor for transition to chronic kidney disease, as AKI is a significant risk factor for developing CKD 5

Discontinue vancomycin immediately to prevent further kidney damage 5
Remove all other nephrotoxic agents, including NSAIDs, aminoglycosides, and ACE inhibitors/ARBs, to minimize kidney injury 5
Adjust all medications for the new level of renal function to avoid further toxicity 5
Avoid further nephrotoxic insults during the recovery phase to promote kidney recovery 5
The American Society of Nephrology recommends discontinuing nephrotoxic medications, such as NSAIDs, aminoglycosides, ACE inhibitors/ARBs, in patients with acute kidney injury 2

For patients with hypervolemia, the American Gastroenterological Association suggests considering diuretics or renal replacement therapy if severe, with a focus on balanced fluid management 6
In patients with cirrhosis, the American Association for the Study of Liver Diseases recommends considering albumin 1 g/kg/day for 2 days if serum creatinine shows doubling from baseline, to prevent further kidney injury 6
The American Gastroenterological Association advises monitoring for fluid overload, especially when administering albumin, due to the risk of pulmonary edema 6
Provide initial fluid resuscitation with isotonic crystalloids at a higher rate than 80 ml/hour, followed by vasopressors once adequate volume has been administered, as recommended by the Journal of Hepatology guidelines 7, 2
The American Journal of Kidney Diseases recommends immediate fluid resuscitation with isotonic crystalloid bolus, preferably balanced crystalloid solution, with an initial bolus of 500-1000 mL given rapidly to restore organ perfusion in patients with AKI and severe hypotension 8
Balanced crystalloid solutions, such as Lactated Ringer's or PlasmaLyte, are the first choice for fluid resuscitation due to their lower risk of hyperchloremic acidosis and association with reduced risk of AKI progression 9
0.9% sodium chloride (normal saline) is an acceptable alternative, but its use should be limited to 1-1.5 L to avoid hyperchloremic acidosis, particularly if balanced solutions are unavailable 8, 9

Provide 20-30 kcal/kg/day total energy intake, and recommend protein intake of 0.8-1.0 g/kg/day in noncatabolic patients without dialysis, as recommended by the Kidney International guideline 7
Prefer enteral nutrition when possible, and consider continuous renal replacement therapy (CRRT) as the first-line modality for hemodynamically unstable AKI patients, as recommended by the Kidney International society 7, 2
Consider RRT when severe metabolic acidosis persists, hyperkalemia is refractory to medical management, volume overload remains unresponsive to conservative measures, or uremic symptoms develop, with a high level of evidence 7, 10, 2

Follow patients who recover from AKI closely, with assessment of serum creatinine every 2-4 days during hospitalization and every 2-4 weeks for 6 months after discharge, as recommended by the American Association for the Study of Liver Diseases 11
Refer patients with AKI to nephrology based on severity, with all Stage 3 AKI patients requiring nephrology consultation, as recommended by the Kidney International and Nature Reviews Nephrology guidelines 2, 5
Adjust or discontinue ACE inhibitors/ARBs in patients with advanced CKD, and use with extreme caution or discontinue in patients with eGFR <30 ml/min/1.73m², as recommended by the American Heart Association 12
Initiate dietary phosphate restriction to 800-1000 mg/day, start phosphate binders with meals, and monitor serum calcium, phosphate, and PTH levels regularly, as recommended by the American Diabetes Association 13
Restrict sodium intake to <2 g/day, and consider potassium restriction if hyperkalemia develops, as recommended by the American Diabetes Association 13