Acute Kidney Injury (AKI) Case Study Simulator

Acute Kidney Injury (AKI): A Comprehensive Guide for Nurses

Acute Kidney Injury (AKI), formerly known as acute renal failure, is a sudden decline in kidney function that occurs over a period of hours to days. It leads to an inability to:

• Excrete waste products
• Maintain fluid and electrolyte balance
• Regulate acid-base status

AKI is a common condition in hospitalized patients and can result in significant morbidity and mortality, making its early recognition and management essential. Nurses play a critical role in the care of AKI patients, providing vital assessments, interventions, and education to optimize patient outcomes.

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Definition and Overview

Acute Kidney Injury is defined by one or both of the following criteria:

• Increase in Serum Creatinine:
  • ≥0.3 mg/dL (26.5 μmol/L) within 48 hours, or
  • ≥1.5 times baseline within seven days
• Reduction in Urine Output:
  • <0.5 mL/kg/hour for more than six hours

The severity of AKI is classified into three stages using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria:

• Stage 1:
  • Serum creatinine 1.5–1.9 times baseline, or
  • Urine output <0.5 mL/kg/hr for 6–12 hours
• Stage 2:
  • Serum creatinine 2–2.9 times baseline, or
  • Urine output <0.5 mL/kg/hr for >12 hours
• Stage 3:
  • Serum creatinine ≥3 times baseline, or
  • Serum creatinine ≥4.0 mg/dL, or
  • Urine output <0.3 mL/kg/hr for >24 hours or anuria

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Pathophysiology of AKI

The causes of AKI are divided into three categories:

Pre-Renal AKI

• Cause: Reduced blood flow to the kidneys, leading to decreased perfusion and filtration
• Common causes:
  • Hypovolemia (e.g., dehydration, bleeding)
  • Heart failure
  • Sepsis
  • Significant blood loss

Intrinsic AKI

• Cause: Direct damage to the kidney structures, including the glomeruli, tubules, interstitium, or vasculature
• Common causes:
  • Acute tubular necrosis (ATN)
  • Glomerulonephritis
  • Vasculitis
  • Nephrotoxic drugs (e.g., aminoglycosides, NSAIDs)

Post-Renal AKI

• Cause: Obstruction of urine outflow from the kidneys
• Common causes:
  • Kidney stones
  • Ureteral strictures
  • Enlarged prostate
  • Bladder outlet obstruction

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Risk Factors

Risk factors for AKI can be modifiable or non-modifiable:

Non-Modifiable Risk Factors

• Pre-existing chronic kidney disease (CKD)
• Advanced age
• Diabetes mellitus
• Hypertension
• Sepsis and systemic infections
• Major surgeries, especially cardiac or abdominal

Modifiable Risk Factors

• Exposure to nephrotoxic medications (e.g., NSAIDs, antibiotics like aminoglycosides)
• Hypovolemia due to dehydration or bleeding

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Clinical Manifestations

The symptoms of AKI vary depending on the underlying cause, but common signs and symptoms include:

General Symptoms

• Fatigue
• Malaise
• Weakness
• Nausea
• Vomiting

Oliguria or Anuria

• Decreased urine output:
• Oliguria: <400 mL/day
• Anuria: <100 mL/day

Edema

• Fluid retention, particularly in the legs, feet, or face

Signs of Electrolyte Imbalance

• Hyperkalemia:
  • Weakness
  • Arrhythmias
• Hyponatremia:
  • Confusion
  • Seizures
• Metabolic Acidosis:
  • Kussmaul respirations
  • Drowsiness

Uremic Symptoms

• Uremic frost
• Pericarditis
• Confusion or encephalopathy in severe cases

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Nursing Assessment

A comprehensive nursing assessment is crucial to identify potential causes and monitor kidney function:

History and Physical Examination

• Identify possible triggers (e.g., recent illness, medication use, volume depletion)
• Assess for signs of hypovolemia, infection, or obstruction

Laboratory Tests

• Serum Creatinine and BUN:
  • Elevated levels confirm AKI
  • A rising BUN:Creatinine ratio may indicate pre-renal AKI
• Electrolytes:
  • Monitor for hyperkalemia, hyperphosphatemia, and metabolic acidosis
• Urinalysis:
  • May show proteinuria, hematuria, or specific casts (e.g., muddy brown casts in ATN)

Imaging

• Renal Ultrasound:
  • Detects structural abnormalities or post-renal obstruction
• CT/MRI:
  • Identifies stones or masses if obstruction is suspected

Special Tests

• Fractional Excretion of Sodium (FeNa):
  • Helps differentiate between pre-renal (<1%) and intrinsic (>2%) AKI
• Biopsy:
  • Performed in selected cases of glomerulonephritis or vasculitis

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Management of AKI

The goals of AKI management are to treat the underlying cause, restore kidney function, and prevent complications.

General Supportive Care

• Monitor fluid status through daily weight, intake/output charts, and vital signs
• Discontinue nephrotoxic medications when possible
• Correct electrolyte imbalances (e.g., calcium gluconate for hyperkalemia)

Treatment Based on AKI Type

• Pre-Renal AKI:
  • Restore perfusion with intravenous fluids (e.g., isotonic saline)
  • Treat underlying causes such as hypovolemia or heart failure
• Intrinsic AKI:
  • For ATN:
    • Supportive care
    • Avoidance of nephrotoxins
  • For Glomerulonephritis:
    • Immunosuppressive therapy
    • Plasmapheresis
• Post-Renal AKI:
  • Relieve obstruction using urinary catheterization, nephrostomy, or surgical intervention

Renal Replacement Therapy (RRT)

• Indications:
  • Severe AKI with refractory fluid overload
  • Hyperkalemia
  • Metabolic acidosis
  • Uremic symptoms
• Options include:
  • Hemodialysis
  • Continuous renal replacement therapy (CRRT)
  • Peritoneal dialysis

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Nursing Interventions

Nurses play a pivotal role in managing AKI patients. Key interventions include:

Monitoring

• Assess changes in urine output and signs of fluid overload (e.g., pulmonary edema)
• Regularly monitor laboratory values, such as creatinine, potassium, and bicarbonate

Fluid Management

• Administer IV fluids as prescribed
• Monitor for signs of fluid overload
• Restrict fluid intake if indicated (e.g., in oliguria or anuria)

Medication Administration

• Ensure proper dosing of medications, considering reduced renal clearance
• Administer prescribed treatments for hyperkalemia, such as:
• Insulin and dextrose
• Sodium bicarbonate

Patient Education

• Teach patients to recognize early symptoms of AKI
• Advise on avoiding nephrotoxic agents
• Educate on the importance of hydration, especially during illness or periods of fluid loss

Infection Control

• Maintain aseptic technique during catheter care or dialysis to prevent infections

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Complications of AKI

If untreated, AKI can lead to severe complications, including:

• Hyperkalemia-induced cardiac arrhythmias
• Pulmonary edema from fluid overload
• Chronic kidney disease (CKD) or end-stage renal disease (ESRD)
• Uremic complications:
  • Pericarditis
  • Encephalopathy

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Prevention of AKI

Preventive measures are essential to reduce the incidence of AKI, including:

• Hydration:
  • Ensure adequate hydration in high-risk patients (e.g., undergoing surgery or receiving contrast media)
• Regular Monitoring:
  • Monitor kidney function regularly in patients with chronic diseases or on nephrotoxic medications
• Patient Education:
  • Teach patients to recognize early symptoms of dehydration or kidney dysfunction

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Conclusion

Acute Kidney Injury is a potentially reversible condition if identified and managed early. Nurses are essential in:

• Early detection
• Monitoring
• Patient education
• Providing care to prevent complications

By understanding the pathophysiology, risk factors, and management strategies for AKI, nurses can deliver high-quality, evidence-based care that improves patient recovery and reduces the risk of long-term kidney damage.