Impaired Renal Function

  1. Prerenal (AKI)
    Inadequate perfusion to the kidneys resulting in decreased glomerular filtration rate (GFR)

    • Causes: Any condition that decreases blood flow, blood pressure or kidney perfusion before arterial blood in the renal artery enters the kidney
    • -sepsis
    • -shock
    • -dehydration

    • Assessment:
    • -underlying cause
    • -GFR decline and oliguria
    • -azotemia/uremia (↑ BUN & Cr)

    • Prognosis:
    • -accounts for 40-80% of the cases or AKI
    • -may be reversed if perfusion quickly restored
  2. Intrarenal (AKI)
    Damage to kidney cells from intrinsic causes

    • Causes:Conditions producing an ischemic or nephrotoxic insult that injures the filtering structures of the kidneys
    • -90% of cases result in acute tubular necrosis
    • -mechanicsms:
    • bacterial infections
    • trauma
    • nephrotoxic injury- endogenous (rhabdomyolosis, sickle-cell), exogenous (IV dye, aminoglycosides, NSAIDS)
    • Ischemic injury (persistent prerenal conditions)

    • Assessment:
    • -BUN and Cr typically begin to rise 48-72 hours and initial insult
    • -Urine studies
    • Myoglobinuria (tea colored urine)
    • hemoglobinuria
    • casts, cellular debris, protein, glucose

    • Prognosis:
    • -usually causes irreparable damage leading to chronic renal failure
    • -ischemia may be reversed if caught early enough
  3. Postrenal (AKI)
    Any obstruction that hinders flow of urine from beyond the kidney

    • Causes: Urine reflux into the renal pelvis, impairing kidney function
    • -bladder obstruction
    • tumor
    • anticholinergic drugs (muscles can't relax to pee)
    • -Ureteral obstruction
    • calculi/stones
    • retroperintoneal fibrosis of hemorrhage
    • -Urethral obstruction
    • strictures
    • BPH

    • Assessment:
    • -risk factors
    • -filter urine
    • -ultrasound
    • -sudden decrease in urine output or anuria (<100ml/24hrs)

    • Prognosis:
    • -Relieve obstruction as quickly as possible (within 48 hours)
    • lithotripsy
  4. Initiation (onset phase)
    • Period from the initial insult until cell injury occurs
    • -GFR decreased due to impairment blood flow to the kidney and decreased pressure within glomerulus
    • -last hours to days, depending on severity
    • -if tx initiated in this phase, damage may be reversible
    • -search for reversible causes and provide appropriate interventions
  5. Oliguric or Anuric Phase
    • <400ml-100ml of urine/24hrs
    • this second phase lasts anywhere from 5-10days

    • Kidney damange becomes apparent and GFR greatly reduced:
    • -accumulation of necrotic cellular debris that may block of urine
    • -accumulation of waste products (BUN, Cr) may cause Asterixis (hand flapping)
    • -electrolyte abnormalities (hyperkalemia, hyperphosphatemia, hypocalemia)
    • -metabolic acidosis

    Closely monitor fluid intake and output with signs of fluid overload

    Maintain fluid restriction or light fluid therapy
  6. Diuretic phase
    Gradual increase of urine with 1-3L/day up to 5L

    • -Third phase may last 1-3 weeks
    • -high urea concentration in the glomerulus and tubules leads to osmsotic diuresis
    • -GFR increases, kidneys able to excrete wastes and fluid, but cannot concentrate urine
    • -Monitor for s/s of hypovolemia, hypotension, dehydration , hyponatremia, and hypokalemia
    • -Near the end of this phase
  7. Recovery Phase
    • Gradual improvement to baseline
    • can take 3-12months to stabilize

    • GFR increases and BUN/Cr levels may return to normal
    • some individuals do not make a full recovery and progress to chronic kidney disease
    • approx 62% recover to normal kidney function, with approx 33% develop residual damage, and 5% require long term dialysis
Card Set
Impaired Renal Function
Renal nursing