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Acute Kidney Injury
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Formerly known as acute renal failure, acute kidney injury (AKI) is a reversible rapid reduction in glomerular filtration rate (GFR) or kidney function, resulting in an increase in serum blood urea nitrogen (BUN), creatinine, and metabolic waste products (Okusa & Rosner, 2023). If left untreated, AKI can lead to reduced urine output, fluid retention, volume overload, and ultimately irreversible loss of kidney cells and nephrons leading to chronic kidney disease.
Definition (Kellum & Lameire, 2012)
The Kidney Disease: Improving Global Outcomes (KDIGO) organization defines AKI as
any of the following:
- Increase in serum creatinine (SCr) by greater than or equal to 0.3 mg/dL (25.6 µmol/L) within 48 hours
- Increase in SCr greater than or equal to 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days
- Urine volume less than 0.5 mL/kg/hour for 6 hours
Classifications of Acute Kidney Injury
(Lippincott Advisor, 2024) |
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Prerenal |
Intrarenal
(Intinsic) |
Postrenal |
Pathophysiology |
Decreased blood flow to kidneys (decreased renal perfusion) |
Structural injury that causes vessel constriction within the kidney |
Blockage along the urinary tract obstructing urine outflow from the kidney |
Causes |
- Absolute decrease in circulating volume (Banasik, 2022)
- vomiting, diarrhea
- hemorrhage
- burns
- dehydration
- Relative decrease in circulating volume
- Systemic vasodilation and hypotension caused by sepsis, anaphylaxis, anesthesia, drug overdose
- Third spacing and edema
- Decreased cardiac output
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- Coagulation defect
- Leukemia, lymphoma
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- Renal calculi
- Emboli
- Prostate enlargement
- Genetic anatomic narrowing
- Intra-abdominal tumors
- Urinary tract strictures
- Kinked or obstructed indwelling urinary catheters
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Contrast-induced AKI (CI-AKI) (Kellum & Lameire, 2012)
CI-AKI [which may also be referred to as contrast-induced nephropathy (CIN)] may occur in patients who receive iodinated radiocontrast for procedures. Patients should be screened for risk factors such as impaired renal function, advanced age, diabetes, hypertension, congestive heart failure, chronic kidney disease, volume depletion, hemodynamic instability, concurrent nephrotoxic medication use and use of large volume and/or high osmolality contrast agents. To minimize risk, consider these strategies:
- Consider alternative methods of imaging studies that do not require the use of contrast.
- Use low dose iso-osmolar or low-osmolar contrast medium through an intravenous (IV) route and the lowest dose possible.
- Begin IV fluids (isotonic sodium chloride or sodium bicarbonate) at least one hour before administration of contrast media and continue for 3 to 6 hours after administration to achieve urine output greater than 150 mL/hour in 6 hours. For patients at increased risk of developing CI-AKI, do not rely on oral hydration alone.
- Withhold potentially nephrotoxic medications prior to contrast administration.