Adult Medical-Surgical Nursing Renal Module: Acute Renal Failure

Acute Renal Failure: GFR  The glomerular filtration rate (GFR) indicates the efficiency of the kidney nephrons:  In concentrating urine to excrete toxins from the body  In maintaining water and electrolyte balance in the body  Average urine output is approximately 1500 ml/ 24 hours

Acute Renal Failure: Classification  A sudden decrease in the glomerular filtration rate (occurring in hours to days)  Oliguria: < 400ml urine output in 24 hours  Anuria: < 50 ml in 24 hours  There may be normal volume but failure to concentrate urine therefore inability to rid the body of waste products  Urine output should be at least 30ml/ hour (400 ml/24 hours) in order to excrete metabolic waste

Acute Renal Failure: Causes  Pre-renal (60% of cases)  Acute Tubular Necrosis (35-40%)  Post-renal (5%)

Acute Renal Failure: Pre-renal Causes (Hypoperfusion)  Pre-renal: hypoperfusion of the kidneys. Impaired blood flow leads to ↓ GFR and urine output  Caused by:  Hypovolaemia (haemorrhage, burns, diarrhoea and vomiting)  Impaired cardiac function  Vasodilation (anaphylactic or septic shock)

Acute Renal Failure: Acute Tubular Necrosis  Direct trauma or toxicity to kidney tissue (nephrons: glomeruli, tubules) from:  Burns } myoglobin from muscle  Crush injuries  ABO incompatibility (agglutination RBCs)  Drugs: including nephrotoxic chemotherapy  Severe infections/ auto-immune reactions: pyelonephritis/ glomerulonephritis

Acute Renal Failure: Post-renal Causes  Obstruction to urine flow in the renal tract leads to back-pressure, progressing to hydronephrosis and ↓ GFR. Caused by:  Tumours  Strictures  Calculi (stones)  Clots  Prostatic hyperplasia

Acute Renal Failure: Four Clinical Phases  Initiation phase: from time of insult to oliguria (hours to days)  Oliguric period: Period of most clinical manifestations and abnormal kidney function tests (KFT) (10-20 days but may be months)  Diuresis: ↑ urine output but urine may be mostly water. Risk of dehydration. Symptoms/ KFT begin to improve (2-3 weeks)  Recovery: Symptoms/ KFT improved (3- 12 months)

Acute Renal Failure: Outcome  Recovery is possible but may not be complete: GFR 1-3% below normal  50% of patients do not recover: acute renal failure may result in death or chronic renal failure

Acute Renal Failure: Effects  Failure of kidney function causes:  Reduced urine volume, fluid retention, circulatory overload, ↑ BP  Reduced urine concentration and excretion of toxic waste products of metabolism, most significantly:  Raised blood urea/ creatinine  Raised potassium: dysrhythmias  Acidic substances: metabolic acidosis

Acute Renal Failure: Clinical Manifestations  Reduced urine output  Weight gain and oedema; hypertension  Lethargy, drowsiness, sleep disturbance, convulsions, coma  Nausea, vomiting, cramps, diarrhoea  Hiccoughs, muscle twitching, restlessness  Cardiac dysrhythmias  Hyperventilation (acidosis)  Dry skin/ mucous membranes, fetor on breath

Acute Renal Failure: Diagnosis  History and clinical picture  Oliguria  Altered KFT:  Raised blood urea, creatinine, potassium, uric acid, phosphates  Low serum calcium  Changes in urine specific gravity  ↑ urine sodium, cellular debris, RBC, WBC, casts  Metabolic acidosis (basal deficit; bicarb ↓ )

Acute Renal Failure: Clinical Management  Treat the cause  Support the patient (ICU) until recovery by:  Dialysis (usually via temporary central line)  Ventilation if necessary  Strict fluid intake restriction  Foley catheter  Diuretics to stimulate kidney function  Monitor for dysrhythmias and overload  Medications

Acute Renal Failure: Nursing Considerations  Care in ICU; on ventilator if necessary  Continuous ECG monitoring  Monitor BP, JVP, oedema (overload)  Strict monitoring of intake/ output  Care of Foley catheter; hourly output (report <30ml)  Monitor progress through general condition, urine output, lab tests  Support relatives

Acute Renal Failure: Medications  Diuretics: stimulate renal function  Insulin and Dextrose } ↓ high blood  Kayexalatepotassium level  Calcium Gluconate  Sodium Bicarbonate: correct acidity  Aluminium hydroxide } correct  Calcium carbonate phosphate/ calcium levels

Acute Renal Failure: Follow-up  Diet: Fluid restriction  Increased CHO (protein-sparing)  Reduced protein initially  Reduced potassium-containing foods  Reduced medication doses as toxic  Monitor progress: urine output, weight, BP, KFT  Monitor for anaemia: erythropoietin ↓