Acute Renal Failure Final

7/29/2019 Acute Renal Failure Final

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Acute Renal Failure


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Acute Renal Failure ( ARF )

- is a rapid loss of renal function due to

damage of the kidneys.

- depending on the duration and severity, a

wide range of potentially life-threatening

metabolic complications can occur.


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- widely accepted criterion for ARF

50% or greater in serum creatinine above

baseline

Urine volume may be normal or changes may

occur. Possible changes include:

Oliguria

Nonoliguria

anuria


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When reductions in renal blood flow

interrupt glomerular pressure; the result is the

development of acute renal failure.

Prerenal ARF occurs in 60% to 70% of cases

- result of impaired blood flow

that leads to hypoperfusion of

the kidney and a decrease in

the GFR.

Categories of ARF


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Intrarenal ARF anything that causes direct

insult to the kidneys.

- Acute tubular necrosis (ATN) isthe most common type of

intrarenal ARF.

Characteristics of ATN:Intratubular Obstruction

Tubular back leak

vasoconstriction

Changes in glomerular permeability


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Postrenal ATF results from obstruction distal

to the kidney.

pressure rises in the kidney

tubules and eventually, the GRF

.


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Causes of ARF

1. Prerenal Failure- volume depletion

- impaired cardiac efficiency

- vasodilation

2. Intrarenal Failure

- prolonged renal ischemia

- nephrotoxic agents- infectious processes


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3. Postrenal Failure

- urinary tract obstruction, including:

Calculi

Tumors

Benign prostatic hyperplasia

Strictures

Blood clots


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Phases of ARF

1. Initiation begins with the initial insultand ends with oliguria develops. This phase

can last from hours to days and is

characterized by:

Renal flow at 25% of normal

Oxygenation to the tissue at 25% of normal

Urine output at 30 ml (or less) per hour

Urine sodium excretion greater than 40 mEq/L.


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2. Oliguric - this phase usually lasts between8-14 days and is characterized by further

damage to the renal tubular wall and

membranes. Other characteristics in the

oliguric phase include:

Great reduction in the GFR

Increased BUN/Creatinine

Electrolyte abnormalities (hyperkalemia,

hyperphosphatemia and hypocalcemia)

Metabolic acidosis


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3. Diuresis - this phase occurs when thesource of obstruction has been removed but

the residual scarring and edema of the renal

tubules remains. This phase usually lasts and

additional 7-14 days and is characterized by: Increase in GFR

Urine output as high as 2-4 L/day

Urine that flows through renal tubules Renal cells that cannot concentrate urine


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4. Recovery - The recovery phase can lastfrom several months to over a year.. Signals

the improvement of renal function. At this

point the GFR has usually returned to 70% to

80% of normal.


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Pathophysiology

decline in renal blood flow (RBF)

decreased glomerular filtration

causes tissue ischemia and eventually cell necrosis or

cell death

produces oxygen free radicals and other enzymes

which exacerbate the problem

sloughing of cells which in turn block renal tubules and

cause a back leak of glomerular filtrate


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Assessment

History

Changes in the urine output

- varies from scanty to a normal volume

- hematuria may be present

- urine has low specific gravity- inability to concentrate urine early

manifestation of tubular damage

- prerenal azotemia: amount of Na in theurine normal urinary sediment

-intrarenal azotemia: amount of Na inurine with urinary cast and cellular debris


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BUN level

- steadily at a rate dependent on the

degree of catabolism, renal perfusion, protein

intake

Creatinine level

- useful in monitoring kidney function


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Assess pts for hyperkalemia

- may lead to dysrhythmias, such as

ventricular tachycardia and cardiac arrest

Progressive metabolic acidosis

- cannot eliminate metabolic load of acid-

type substances produced by the normal

metabolic processes


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There may be an increase in blood phosphate

concentrations

Calciums level may be low

Anemia as a result of reduced erythropoietin

production, uremic GI lesions, reduced RBC

lifespan and blood loss from the GI tract


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Diagnostic studies

- ultrasonography effective in

determining existing renal failure and/orobstruction of the urinary collecting system

- CT or MRI scan may show evidence of

anatomic changes

-Creatinine Clearance Test this is

believed to be the most accurate test to

determine glomerular filtration rates- blood exam


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- urinalysis

- renal biopsy only be done if the result will

alter the treatment plan

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Acute Renal Failure Final