Acute Kidney Injury (AKI) Overview

• Acute Kidney Injury (AKI) is also known as Acute Kidney Failure

Functions of the Kidney

• Eliminates metabolic waste
• Regulates blood pressure
• Produces erythrocytes
• Activates Vitamin D
• Autoregulates blood flow
• Balances acid-base levels
• Balances fluids and electrolytes

Acute Kidney Injury (AKI)

• Sudden failure of renal function is caused by decreased perfusion, intrarenal disease, or obstruction
• Decreased glomerular filtration rate (GFR) leads to metabolic waste build-up, and a loss of homeostasis

Causes of AKI

• Prerenal causes include decreased perfusion, dehydration, hemorrhage, and sepsis
• Intrarenal causes include direct kidney damage from trauma and surgery and are classified as tubular, glomerular, interstitial, and vascular
• Postrenal causes include obstruction, e.g. kidney stones, enlarged prostate, bladder not emptying, blood clots, and cancer

Acute vs Chronic Renal Failure

• Acute Renal Failure:

  • Happens suddenly
  • Caused by hypoperfusion due to low BP, dehydration, hemorrhage, sepsis, etc
  • Assessed by increased BUN and creatinine, anemia, oliguria, hypocalcemia, hyperphosphatemia, metabolic acidosis, and hyperkalemia
  • Managed by correcting hypoperfusion with fluids or sepsis treatment and may require CRRT in the ICU

• Chronic Renal Failure:

  • Happens over months or years
  • Typically due to disease like Diabetes and/or hypertension
  • Assessed by increased BUN and creatinine, decreased GFR, hyperkalemia, hyperphosphatemia, hypocalcemia, metabolic acidosis, anemia, oliguria, fluid volume excess (FVE), and edema
  • Managed with dialysis, peritoneal dialysis, or CRRT in the ICU

Dialysis

• Indicated by Acid/Base disturbances, Electrolyte disorders, Intoxication from lithium or antifreeze, Fluid Overload, or Uremia/Azotemia

Azotemia vs Uremia

• Azotemia is when there's nitrogen in the blood
• Uremia occurs when there's urea in the blood

Types of Dialysis

• Hemodialysis involves blood with waste products that pass through a membrane, exiting fluids to a dialysate line
• Peritoneal Dialysis involves dialysis solution in the abdomen, draining out waste, fluid, and chemicals through a peritoneal membrane
• Continuous Renal Replacement Therapy (CRRT)

CRRT Defined

• CRRT is Continuous Renal Replacement Therapy
• It is a slow therapy to remove fluid for hemodynamically unstable patients
• Occurs over 24 hours per day
• Suited for clients who cannot tolerate normal hemodialysis
• Requires a 1:1 nurse ratio
• Less stress occurs on the heart due to longer periods

Ultrafiltration

• Ultrafiltration is the movement of fluid through a membrane caused by a pressure gradient that facilitates fluid volume reduction

CRRT vs Hemodialysis

• CRRT:
  • Continuous
  • Can utilize venous access
  • Less hemodynamic instability
  • Fluids and electrolytes are constantly adjusted
• Hemodialysis:
  • Intermittent
  • May use arterial access
  • Greater hemodynamic instability
  • Faster clearance related to greater flow rates

Disadvantages of CRRT

• Requires specialty education and is labor-intensive for bedside RNs
• Can cause frequent clotting of filter and access
• Requires anticoagulation
• Increases patient acuity
• Decreases patient mobility
• Medication dosing is based on a 24-hour run

Why Use CRRT?

• Minimal changes in plasma osmolality occur
• It provides better control of azotemia, electrolytes, and acid/base status
• Easier parenteral nutrition and medication administration
• Effective fluid removal
• Able to remove large molecules with cardio-depressant, vasodilatory, and inflammatory properties
• Able to remove toxins