AKI Flashcards
DEFINITION OF AKI
- Rapid loss of kidney function
- Rise in serum creatinine or reduction of urine output
- Can develop azotemia (increase in nitrogenous waste)
AKI most common causes
-Hypotension, Hypovolemia, Exposure of nephrotoxic agents
most common reason for AKI in the hospital
- prerenal causes
- acute tubular necrosis (ATN)
Pre renal
- is due to factors external to the kidney that reduce circulation causing reduction in renal blood flow and decreased glomerular perfusion
- body will compensate in prerenal AKI to increase blood flow by increasing blood volume angiotensin II, aldosterone, norepinephrine, and antidiuretic hormone to.
- can lead to intrarenal.
Intrarenal
- caused by direct damage to the kidney tissue which leads to impaired nephron functioning
- Causes for this can be prolonged ischemia, nephrotoxins, hemoglobin release from hemolyzed RBCs, or myoglobin released from necrotic muscles cells
- ATN could be a cause
post renal
- caused by mechanical obstruction of urinary flow and is below the kidneys
- 10% of AKI
- most common cause is BPH, prostate CA, calculi, trauma, or external tumors
- If you have bilateral ureter obstruction this can lead to hydronephrosis.
- If a blockage is fixed within 48 hours there generally is complete recovery.
acute tubular necrosis (ATN)
- Caused by disruption in the basement membrane and patchy destruction of the tubular epithelium
- Nephrotoxic agents cause tubular epithelial cells to slough off and plug the tubules.
- nephrotoxic agents build up and plug the tubules of the kidney which alters the ability of the kidney to filter appropriately.
- can be reversed death from AKI in the hospital can be high
Risk stage of RIFLE
- Serum creatinine incresed by 1.5 or GFR decreased by 25 %
- urine output is less than 0.5 ml/kg/hr fro 6 hr
Injury phase of RIFLE
- serum creatinine increased by 2 or GFR decreased by 50%
- UO less than 0.5 for 12 hours
Failure stage of RIFLE
- serum creatinine increased by 3 or greater than 4 mg with acute rise of more than 0.5 mg GFR decreased by 75%
- UO less than 0.3 for 24 hours (oliguria) or anuria for 12 hours
Loss stage of RIFLE
- persistant acute kindey failure; complete loss of function > 4 weeks
end stage kidney disease stage of RIFLE
-complete loss of kidney function > 3 months
oliguric phase
- reduction of urine output of less than 400mL/day and can occur within 1-7 days of injury
- lasts 10-14 days
- 50 % of people may not experience this
- The longer in the oliguric phase the poorer the prognosis
- changes in UO do not always correspond to changes in GFR. Rather the changes in urine output can help determine the cause. Further diagnostics can be done to determine the cause of AKI.
difference in oliguria and nonoliguria
- Nonoliguric have a higher GFR than oliguric patients and/or they may reabsorb less in the tubules.
- The difference in urine output between oliguric and nonoliguric ATN may be due to variations in GFR or in the rate of tubular reabsorption
- Treatment based on oliguria vs. nonoliguria
diuretics with oliguric ATN
- does not shorten the duration of renal failure, decrease the requirement for dialysis, or improve survival and might delay timely initiation of dialysis.
- Among patients with oliguria and established ATN, diuretics should not be used as a possible therapy of ATN. -Diuretics may be given for a short length of time for volume control, but such use should not postpone the initiation of dialysis (if required).
- However, giving crystalloids maybe appropriate depending on the cause like if the person is hypovolemic.
clinical manifestations during the oliguric phase
- fluid volume- retention to due to hypovolemia
- metabolic acidosis: not excreting enough hydrogen
- Sodium balance: cannot conserve sodium so urine has high sodium and serum has low to normal levels
- Potassium excess: K+ > 6mEqL emergency
- Hematologic disorders: leukocytosis
- Waste product accumulation: increase urea
- Neurologic disorders: build up of waste = fatigue, difficulty concentrating, stupor, coma
fluid volume in oliguric phase
- retention is occurring because of hypovolemia.
- By repleting fluids, issues can be resolved.
- However, in some cases there can be fluid overload such with anuria where neck veins could be distended or other complications like pulmonary edema or HF can occur.
metabolic acidosis in oliguric phase
-This can occur because the kidneys cannot excrete hydrogen. Acid builds up. Serum bicarbonate is depleted and production is decreased.
sodium balance in oliguric phase
- The damaged tubules cannot conserve sodium so urine has high amounts of sodium and normal to lower levels of serum NA.
- Always be careful on replacement of NA because excess intake of NA can cause volume expansion. Likewise, hyponatremia can lead to cerebral edema.
potassium excess in oliguric phase
- Kidneys normally excrete potassium
- with AKI they are not able to do that.
- monitor for peaked T waves and widening of the QRS and ST segment depression.
hematologic disorders in oliguric phase
-Leukocytosis (high WBC) is often present with AKI and the most common cause of death in AKI is infection.
waste product accumulation in oliguric phase
Normally kidneys excrete urea the end product of protein metabolism, this will be increased with AKI.
neurologic disorders in oliguric phase
as nitrogenous waste builds people can experience fatigue and difficulty concentrating and eventually seizures, stupor and/or coma.
Urine analysis for oliguric phase
- RBCs
- Casts
- WBCs
- Specific gravity 1.010
- Osom: 300 mOsm/kg (this is the same osom of plasma which means there is tubular damage and the kidneys can no longer concentrate urine)
- Proteinuria (if related to glomerular membrane dysfunction)
diuretic phase
- Begins with gradual increase in UO
- May last 1-3 weeks
- normalizing of acid-base
- electrolyte and waste product parameters indicate improvement of renal failure
- Nephrons still cannot concentrate urine, but the kidneys can now excrete wastes
- Assess for hypovolemia and hypotension from fluid loss – replace fluids
- Assess for hyponatremia, hypokalemia and dehydration (Since the nephrons can excrete waste now but not concentrate it)
recovery phase
- Begins when Glomerular Filtration Rate increases, allowing BUN and creatinine levels to plateau/decrease
- Improvement can occur up to 12 months
AKI dx
- Hx
- UA
- Labs
- Ultrasound
- Renal scan
- CT
- Renal biopsy
prerenal causes
hx of cardiac dx, dehydration, blood loss
intrarenal causes
nephrotoxic meds, blood transfusion, exposure to contrast media
postrenal causes
hx changes in urinary stream, hematuria, stones, ca of bladder or prostate