Acute renal failure (ARF) - PowerPoint Presentation

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Acute renal failure (ARF)

acute kidney injury AKI is a sudden and usually reversible loss of renal function which develops over days or weeks and is usually accompanied by a reduction in urine volume.

A rasied creatinine level can be due to acute, acute on chronic of chronic kidney disease.

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Two small kidneys on ultrasound indicate chronicity.

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Causes of ARF

Pre renal

Systemic

Heart failure

Blood/ fluid loss/ shock called hypovolemia

Local

Renal artery stenosis

Disease affecting arterioles

Under perfusion initially causes rapidly reversible changes,. Subsequently, acute tubular necrosis that may lead to intrinsic renal failure.

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Intrinsic renal disease

Toxic /septic renal failure 85%

glomerular diseases 5%

Primary

Component of systemic disease

Interstitial disease 10%

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Post renal causes

Obstruction

Stones

Tumor

Enlarged prostate

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Reversible pre renal acute renal failure

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Pathogenesis

The kidneys can regulate its own blood flow and GFR over a wide range of perfusion pressure

When the perfusion pressure falls—as in hypovolaemia, shock, heart failure or narrowing of renal arteries—the resistance vessels in kidneys dilate. It is mediated by prostaglandins.

(this is impaired by NSAIDS)

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if autoregualtion of blood is fails, the GFR can stillbe maintained by selective constriction of efferent arteriols by rennin angiotensin mechanism ( it is inhibited by ACE inhibitors)

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More sever or prolonged under perfusion of kidneys may lead to failure of these compensatory responses, and acute fall in GFR. This leads to formation of low volume concentrated urine (osmolality >600mOsm/kg) but low in sodium (<20mmol/l)

Note these changes may be absent in patient with pre existing renal impairment or those who received diuretics

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Clinical features:

Marked hypotension

Signs of hypoperfusion such as delayed capillary return, cool peripheries etc.

Postural hypotension is reliable sign of early hypovolemia.

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The causes reduces renal hypo perfusion

The sign suggesting following may be present

Shock

Blood loss

Crush injuries

Burns

Sepsis

These causes should be assessed

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Management

Establish and correct the under lying causes is very important step.

Treat hypovolemia with restore blood volume as soon as possible ( with blood, plasm, isotonic saline 0.9%)

Optimize systemic haemodynamics. Monitoring the central venous pressure and pulmonary wedge pressure is necessary for fluid administration.

Note: Meta analysis trials do not support the role of low dose dopamine in ARf.

Correct the metabolic acidosis

Restoring the blood volume will correct the acidosis by restoring the kidney function.

Sodium bi carbonate (50 ml of 8.4%) may be used severe acidosis.

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Prognosis

Good full recovery of renal function if early treatment is given.

In some case treatments is ineffective and renal failure becomes established.

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Established acute renal failure (ARF)

Acute renal failure (ARF) may develop follwing severe and prolonged underperfusion of kidneys when the histological pattern of acute tubular necrosis is usually seen.

Acute tubular necrosis (ATN)

It is necrosis of renal tubular cells may result from ischemia of nephrotoxicity caused by chemicals, bacterial toxins or combination.

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Drugs includes

Aminoglycosides antibiotics like gentamicin, the cytotoxic drugs cisplastin, anti fungal amphotericin B.

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Fortunately there is good recovery because renal tubular cells can regenerate and reform basement membrane.

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Features of established ARF

These show the causal conditions

Urea and creatinine

Raised urea and creatinine

Alterationin urine volume

Oliguria/ anuria

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Disturbance in fluid, electrolytes and acid base balance

Hyperkalaemia

Due massive tissue breakdown, hemolysis, and metabolic acidosis.

Dilutional hyponatraemia

Oliguric patient continue to drink of excessive fluid is given

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Metabolic acidosis

Hypocalcaemia

Reduced renal production of 1,25 dihydroxychlocalciferol

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Uremia

Uremic features:

Anorexia

Nausea and vomiting

Drowsiness

Apathy, confusion

Hiccups

Fits, coma and death.

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Respiratory features

Inc resp. rate

due to acidosis

infection

pulmonary edema due to excessive fluid administration

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Blood

anemia

Bloold loss

Hemolysis

Dec.erythropoetin secretion.

Platelets and cogulation dysfunctions.

Severe infection

Depressed immunity.

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Management

Initial Management is targeted at following priorities:

Hyperkalemia

Pulmonary edema

Infection

Uremia itself

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Hyperkalemia

i.v calcium gluconate (10ml of 10% solution)

Inhaled

β

2 agonist e.g salbutamol

i.v glucose (50ml of 50% solution)

Insulin 5 U actrapid

Intravenous sodium bicarbonate.

Iv lasix and normal saline.

Ion exchange resin ( resonium) orally or rectally

Dialysis

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Immediate fluid management

Volume replacement

CVP monitoring

Pulmonary edema may require dialysis to remove water and sodium from the body.

Temporary respiratory support

CPEP

IPPV

Severe acidosis may require sodium bi carbonate if volume status allows

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Addressing the underlying causes of ARF

Remove post renal obstruction

Uretric dilation

Prostate surgery

Percutaneous nephrostomy

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No specifis treatment of ATN

immuno suppressive drugs for rapidly progressive glomerulo nephritis.

Plasma exchange in micro angiopathic disease.

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FlUID AND ELECTROLYTE BALANCE

After initial resusitation,

Maintain I/O chart

Daily weight

Daily intake should equal the urinr out put plus 500 ml to cover insensible loss.

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Protein and energy intake

By dietary protein restriction ( 40g per day), in whom dialysis is likely to be avoided.

Patients on dialysis may require more dietary proteins ( 1 g / kg proteins daily and 10-12g nitrogen).

Adequate energy is needed in hypercatabolic states like sepsis and burns.

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Infection control

Treated accordingly with porper antibiotics.

dose adjustment is required.

Drugs like NSAIDS and ACE inhibitors should usually be avoided.

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Renal replacement therapy

This may be required as supportive management in ARF.

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Prognosis

In uncomplicated ARF, due to blood loss, hypovolemia, mortality is low.

In ARF associated with serious infection/ sepsis and multi organ failure , mortality is 50 to 70 %.

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