AKI and Dialysis Flashcards
What are 2 main types of insults in AKI?
1) Acute ischemia –> Patchy lesions along proximal and distal tubules, basement cell membrane is affected and necrosis is present
2) Acute toxic –> Basement membrane usually left intact, tubular destruction ranges from swelling to necrosis, damage is generalized and widespread
What are the 3 main categories of AKI?
1) Prerenal
2) Intrarenal
3) Postrenal
What is prerenal failure?
Physiological response to insult that occurs before blood reaches kidney.
Result in renal hypoperfusion, decrease GFR, oliguria.
Nephrons remain normal and can recover
What are causes of pre-renal failure?
Local causes: Emboli, thrombus, surgery, hepatorenal syndrome
General causes: Hypoperfusion, decreased CO
What is intra-renal failure?
Parenchymal damage to nephrons resulting from disease or nephrotoxic agents. Damage can involve both glomerulus and tubular epithelium
**ATN (Acute Tubular Necrosis)
What causes intra-renal failure / ATN?
Nephrotoxic or ischemic injury to the renal tubular epithelium. Damage can extend to the basement membrane
What are the differences between Ischemic vs toxic ATN?
Ischemic: Damage is irregular along PCT and DCT, failure of autoregulatory properties of afferent and efferent arterioles that regulate GFR. ***Basement membrane damaged and necrotic
Toxic: Some nephrotoxins are vasoconstrictors (contrast dye), uniform widedspread damage to tubules range from swelling to necrosis. ***Basement membrane not as severely injured
What is pathophys of ATN?
Inflammatory process Tubular swelling, cast formation (cellular debris) Obstruction decrease capillary BF Ischemia, cell injury Decrease O2, ATP Decrease cell function O2 free radicals attract Ca intracellularly Decrease serum Ca Further injury
Why do AKI pts become anuric?
Glomerular pressure equals hydrostatic pressure.
Obstructions increase tubular hydrostatic pressure that eventually equals filtration pressure
What is postrenal failure?
Physiological response caused by disruption of urine flow from urinary tract to bladder.
Rare but accounts for most anuric cases.
What are the 4 stages of acute renal failure?
1) Initiation (onset phase)
2) Maintenance (oliguric / anuric phase)
3) Diuretic
4) Recovery
What happens in initiation phase?
Time of onset to cell damage, decrease in GFR due to impaired renal BF. Glomerular filtrate backleaks into tissues.
Pt has fatigue, fluid retention, anemia, decreased UO
What happens in maintenance phase?
Oliguria, severe decrease GFR with excessive H2O retention leading to dilutional hyponatremia
Increased K –> due to decreased excretion, muscle breakdown
Increased H+ –> leading to metabolic acidosis
Anemia –> due to suppressed erythropoietin
Creatinine, urea, phosphate elevated –> Muscle breakdown and inability to excrete waste
Hypocalcemia –> Decreased gut absorption due to decreased Vit D activation in kidney and O2 free radicals attracting calcium intra-cellularly
Azotemia (Buildup of metabolic waste)
What happens in the diuretic stage?
GFR begins to increase, reabsorption might not follow for a while. Gradual increase in UO
May have polyuria and dehydration d/t INABILITY TO CONCENTRATE URINE
Kidneys can clear volume but not solutes
What happens in recovery stage?
GFR returns to 70-80% normal
BUN and Cr may never completely normalize
Final stage is ability to concentrate urine