Acute Kidney Injury Flashcards
(21 cards)
What is Acute Kidney Injury (AKI)?
- abrupt loss of kidney function and GFR over a period of hours to days
- reversible
What are the three classifications of AKI?
- prerenal
- intrarenal
- postrenal
What causes prerenal AKI?
Decreased blood flow to the kidney
What are situations that cause blood volume depletion?
- Hypovolemia
- Hemorrhage
- Gastrointestinal (GI) losses
- Vasodilated states (shock)
What causes intrarenal AKI?
Direct damage to the kidney tissue
What are situations that cause damage to the kidneys?
- Ischemia and possible necrosis
- Nephrotoxic drugs
- Radiographic contrast dyes
- Myoglobinemia
- Blood transfusions
What causes postrenal AKI?
Obstruction of urine outflow, leading to backflow of urine in the kidneys
What are situations that cause obstruction of urine outflow?
- Calculi in the urinary tract
- Enlarged prostate (BPH)
- Strictures
- Tumors
- Congenital defects
What is the normal range for GFR/eGFR?
110–125 mL/min/1.73m²
What is the normal range for cardiac output?
5–7 L/min
What is the relationship between cardiac output and normal kidney function?
- kidneys receive ~20-25% of CO
- ↓ cardiac output → ↓ renal perfusion, leading to prerenal AKI
What is the significance of mean arterial pressure (MAP) in kidney function?
- Normal MAP: 70-110 mmHg
- kidneys need a MAP of ≥ 65 mmHg for adequate perfusion
- lower MAP can cause AKI due to ischemia
MAP represents blood to vital organs and tissues
Why is N-acetylcysteine given with contrast dye?
- protects the kidneys by increasing the excretion of toxins
administered orally or IV
What are the 4 phases of AKI?
- Initiation
- Oliguric/Anuric
- Diuretic
- Recover
Describe initiation phase.
Injury begins, no major symptoms yet
Describe oliguric/anuric phase.
- ↓ urine output (< 400 mL/day)
- hypervolemia
- fluid retention
Describe the diuretic phase.
start of healing process
Describe the recovery phase.
- improved kidney function and energy level
- mostly everything is back to normal
What fluid, electrolyte, and lab changes occur in the oliguric/anuric phase?
- ↓ GFR (115-125 ml/min)
- ↑ BUN (10-20 mg/dL)
- ↑ Creatinine (0.6-1.2 mg/dL)
- ↑ Potassium (3.5-5.0 mEq/L)
- Metabolic acidosis (H+ retention, ↓ HCO₃)
What compensatory mechanism could occur if the patient develops metabolic acidosis?
Hyperventilation
trying to get rid of extra CO₂
What fluid, electrolyte, and lab changes occur in the diuretic phase?
- ↑ GFR
- ↑ urine output → dehydration, hypotension
- ↓ BUN/creatinine (still abnormal)
- risk of metabolic alkalosis (due to H+ loss)
