Paediatrics: Acute kidney injury - diagnosis and treatment

2021-03-04 12:00 AM

The following urinary indices may be helpful providing no diuretics have been given.

Diagnosis

To accurately interpret the fractional excretion of sodium (FENa), patients should not have recently received diuretics. FENa is greater than 1% (and usually greater than 3%) with acute tubular necrosis and severe obstruction of the urinary drainage.

FENa = [(UNa × PCr)/(PNa × UCr)] × 100

where UNa and UCr are urinary Na and creatinine, respectively, and PNa and PCr are plasma Na and creatinine, respectively.

Treatment

Liaise with a paediatric nephrology centre early and treat the following.

  • Hyperkalaemia (K+>6.5mmol/L;).
  • Metabolic acidosis.
  • Hypertension.
  • Shock.
  • Fluid overload.
  • Hypocalcaemia.
  • Hypo/hypernatraemia.

Specific treatment depends on the underlying cause. However, the following general management principles apply:

  • Observations: daily weight, BP, strict fluid input and output monitoring.
  • Fluids management: Pre-renal-fluid bolus (10mL/kg of 0.9% saline)and furosemide. Otherwise, restrict to insensible losses (400mL/m2) + urine output. Consider adding diuretic therapy.

Electrolytes: monitor at least 12-hourly until stable. K+ and PO4 restricted diet. Consider adding a PO4 binder.

  • BP: treat hypertension.
  • Medications: adjust drug doses according to the level of renal impairment.

The patient may require transfer to a paediatric nephrology centre if dialysis looks likely or there is uncertainty about the diagnosis.

Indications for dialysis

The following are indications for urgent dialysis in ARF.

  • Severe hyperkalaemia.
  • Symptomatic uraemia with vomiting/encephalopathy (usually urea >40mmol/L).
  • Rapidly rising urea and creatinine.
  • Symptomatic fluid overload, especially cardiac failure or pericardial
  • effusion.
  • Uncontrollable hypertension.
  • Symptomatic electrolyte problems or acidosis.
  • Encephalopathy or seizures.
  • Prolonged oliguria: conservative regimen controls ARF, but causes nutritional failure.
  • Removal of exogenous toxins or metabolite (inborn error).

Note: Patients with the haemolytic–uraemic syndrome should be referred as soon as the child becomes oliguric or if urea is raised as current practice is to dialyse early to reduce neurological complications and to allow transfusion.

  • Acute dialysis-methods
  • Peritoneal dialysis (abdominal catheter).
  • Haemodialysis (femoral or jugular access).
  • Haemofiltration (usually continuous venovenous haemofiltration).