Acute Kidney Injury

Acute Kidney Injury

1. Sudden decrease in renal function

   • Build up of waste, fluid, and electrolyte imbalane
     • Can be reversible!!!

2. Causes

   • Pre-renal: issue with perfusion to kidney, decreases kidney function, decrease blood to kidney to filter and deprives kidney of nutrients
     • Ex: MI, bleeding, dehydration, burns
   • Intra-renal: damage to the nephrons, causing decreased ability to filter blood, remove waste and excess water, and maintain electrolyte levels.
     • Ex: nephrotoxic drugs (NSAIDs, chemo drugs, contrast dye, aminoglycosides), infection (glomerulonephritis), injury
   • Post-renal: block in the urinary track after the kidney to the urethra, that prevents urine draining out of the system. This increases pressure in the kidney, increases waste, and this decreases kidney function.
     • Ex: renal calculi, enlarged prostate, neuro injury, stroke (bladder doesn't empty properly)

3. Phases

   • Oliguric
     • Urine output less than 400 mL/day due to glomerulus decreased ability to filter blood (decreased GFR)
     • Increase BUN, increase creatinine, neuro changes, itching, hyperkalemia, increased fluid in the body (edema, pulmonary issues), metabolic acidosis
     • Nursing interventions: low protein diet, restrict potassium foods, monitor EKG, I & O, daily weights, O2
   • Diuresis
     • Nephrons on their way to recovery. Filters blood but cannot concentrate urine.
     • GFR starts improving, BUN and creatinine decrease, patients mental status increases
     • Patient voiding 3-6 L per day due to osmotic diuresis, this can cause hypovolemia, dehydration, hypotension, hypokalemia
   • Recovery
     • When GFR returns to normal
     • Urine output is 1-2 L , BUN and creatinine is normal, electrolytes are balanced

4. Creatinine

   • Waste product from muscle breakdown
   • 0.6 - 1.20 mg/dL, increase creatinine level, decrease kidney function
   • Solely filtered from blood via glomerulus and is not reabsorbed or secreted in the nephron, which is why its a good indicator of kidney filtering ability.
   • Creatinine clearance: the amount of blood the kidneys make per minute that is free of creatinine

5. GFR

   • Normal: 90 mL/min or high (rate of blood flow through the kidneys
   • Decreased GFR = decreased urine output, increased water in the body, increased waste and electrolyte imbalance

6. BUN

   • 6 - 20 mg/dL
   • Protein breakdown by liver, secreted in blood and filtered by the kidneys

7. Treatment

   • Temporary hemodialysis, antihypertensives, medications to balance electrolytes, diuretics, renal diet