Page 399 - Critical Care Nursing Demystified

384 CRITICAL CARE NURSING DeMYSTIFIED

necrosis (ATN). ATN occurs when destruction of tubular epithelial cells results
in increased intraluminal pressure, which greatly reduces GFR and renal func-
tion. Direct damage of the nephrons or cortex results in tubular swelling
and then necrosis, thus the title ATN. Debris from swelling and necrosis leads
to blocking blood and filtrate flow further leads to stasis of urine and more
necrosis.
Other causes of intrarenal failure include acute glomerulonephritis, nephro-
toxic drugs (contrast dye, aminoglycoside antibiotics) and ischemia.
Postrenal failure is basically obstructive in nature. Obstructions can occur
anywhere in the kidney or the ducts and organs that drain to the urethra.
Abnormalities like kidney stones or tumors can lead to backup of urine and
stasis leading to dilation of the system, increased GFR, and increased edema
from water and sodium reabsorption and infection.
No matter where the renal failure occurs, the end result of this insult will
lead to retention of wastes, chiefly nitrogen and electrolytes, and metabolic
acidosis, which can lead to organ failure.

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A large amount of radiographic dye is injected during arteriograms of many organs
like the heart, brain, and kidney. ATN from intrarenal failure can start 48 hours after
drug administration and peak in 3 days. If the patient is discharged earlier than these
times, nursing teaching at discharge regarding signs/symptoms of ATN is imperative
to preserve kidney functioning.

TABLE 8–7 Types of Acute Renal Failure (ARF)

Type of ARF Location of Failure Causes
Prerenal failure Reduced blood flow Decreased blood supply* from low
(60% of cases) to kidneys cardiac output disorders like
dysrhythmias, cardiogenic shock,
heart failure and MI
Hypovolemia from burns, diuretics,
dehydration, hemorrhage, shock,
sepsis, and trauma
Severe vasoconstriction from DIC
High doses of dopamine ACE
inhibitors/ARBs in combination
with diuretics
Mechanical ventilation with PEEP