Neobook — clinical reference

Definition

Sudden reduction in renal function resulting in azotemia and disturbed metabolic fluid and electrolyte balance.Abnormal Na+ and K+ = emergency. If renal failure suspected, do not assume it was a haemolysed specimen. Do blood gas and formal K+ urgently.

Clinical

History and signs of underlying disease
Vomiting / lethargy / anorexia / tachypnoea & acidotic breathing
Fluid imbalance – oedema / pulmonary oedema / hypertension
Decreased urine output
Encephalopathy / twitching / seizures

Causes of acute renal failure

Pre-Renal	Shock/hypovolaemia/dehydration Haemorrhage Burns with 3rd space losses
Intra-Renal	Nephritis Acute tubular necrosis Haemolytic uraemic syndrome Pyelonephritis Toxins Renovascular disease
Post-Renal	Post urethral valves Ureteric obstruction (bilateral) Masses

Investigations

Urine: Dipstix and send to lab for chemistry. Measure intake and output (may require catheterization)
Fractional excretion of Sodium =
Blood: Gas / U&E / Ca+ Mg + Phoshate / Protein / Albumin / FBC + Diff + Smear
Radiology: CXR / urgent renal ultrasound

	Pre-Renal	Intra-Renal	Post-Renal
Urine SG	>1020	<1000	-
Urine Osmolality	> 500	< 300	300 - 400
Urine/Plasma Osmol	>1.3	<1.3	-
Urine/Plasma Creat	>40	<20	<20
Urine Na (Meq/l)	<20	>40	>40
Fe Na	<1%	>2%	>3%

Management

Treat underlying cause = if hypovolaemic / shock give crystalloid in 5 ml – 10 ml/kg boluses and reassess regularly.
Avoid potassium containing fluid if potassium is raised (and treat hyperkalaemia)
If oliguria persists after correcting fluid deficit, try lasix 1 mg – 4 mg/kg slow IV.
Record intake:output strictly (catheterise)
Give insensible losses only to begin with – especially if overloaded = 30 ml/kg/day. Choose fluid according to U&E results: may need to start with 5% - 10% dextrose/water initially.
Monitor and treat raised BP.
Seizures: IV Lorazepam 0,1 mg/kg
Rectal Diazepam 0,5 mg/kg

Indications for dialysis

Anuria unresponsive to aggressive diuretic treatment
Severe fluid overload causing pulmonary oedema unresponsive to diuretic treatment
Uncontrollable Hyperkalaemia or hyponatraemia not responding to conservative treatment
Uncontrollable metabolic acidosis (pH < 7,1) or serum bicarbonate < 10 mmol/L.
Uraemic: Altered level of consciousness / seizures / bleeding diathesis
Inborn error of metabolism; especially if ammonia is increased
Central nervous system signs, e.g. convulsions or coma.
Severe hyperphosphataemia and hypocalcaemia.
Uncontrollable hypertension.

Acute Renal Failure

Drugs mentioned