Renal failure

  • Reduction in renal excretory or regulatory function
  • Results in the retention of waste products normally excreted by the kidney
  • Normal adult urine output = 0.5 ml/kg/hr
  • Renal failure can be:
    • Anuric
    • Oliguric
    • Polyuric

Causes of acute renal failure

Type Causes
Pre-renal failure Hypovolaemia secondary to acute blood or plasma loss
Fluid and electrolyte depletion 
Hypotension secondary to cardiogenic shock 
Hypotension secondary to sepsis
Intrinsic renal failure Acute tubular necrosis due to prolonged renal hypoperfusion
Acute tubular necrosis due to contrast nephropathy 
Acute glomerulonephritis 
Drug induced nephrotoxic damage  
Athero-embolic disease 
Acute pyelonephritis
Renal outflow obstruction Calculi 
Blood clot  
Ureteric damage and ligation  
Prostatic hypertrophy

Biochemical changes of acute renal failure

  • Hyponatraemia
  • Hyperkalaemia
  • Hypocalcaemia
  • Metabolic acidosis

Urinary biochemistry

  • In pre-renal failure
    • Urine specific gravity - >1.016
    • Low urinary sodium - <20 mmol/l
    • High urinary urea - >250 mmol/l
    • High osmolality - > 500 mosm/kg
  • In intrinsic renal failure
    • Urine specific gravity - <1.010
    • High urinary sodium - >40 mmol/l
    • Low urinary urea - <185 mmol/l
    • Isotonic urine - 300-350 mosm/kg

Management of renal failure

  • Remove precipitating cause
  • Most surgical patients are hypovolaemic
  • Require volume resuscitation
  • If inadequate perfusion pressure consider inotropic support
  • Oxygen
  • Consider bicarbonate if
    • Base excess > 10
    • Arterial pH <7

Hyperkalaemia

  • Requires urgent treatment if
    • Symptomatic
    • ECG changes - increased pr interval, tented t waves, ventricular tachycardia
    • Serum potassium > 6 mmol/l
  • Treatment options
    • 10 ml 10% calcium chloride intravenously
    • 10u Actrapid in 50 ml 50% dextrose
    • Salbutamol nebuliser
    • Calcium resonium 15-30 mg pr twice daily

Bibliography

Esson M L,  Schrier R W.  Diagnosis and treatment of acute tubular necrosis.  Ann Int Med 2002;  137:  744-752.

Kapadia F N,  Bhojani K, Shah B.  Special issues in the patient with renal failure.  Crit Care Med 2003;  19:  233-251.

Mehta R L,  Clark W C,  Schetz M.  Techniques for assessing and achieving fluid balance in acute renal failure.  Curr Opin Crit Care 2002;  8:  5350543.

Singri N,  Ahya S N,  Levin M L.  Acute renal failure.  JAMA 2003;  289:  747-751.

 

 
 

Last updated: 09 November 2010

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