Acute Kidney Injury (AKI)

Definition

Abrupt loss of kidney function leading to decreased glomerular filtration rate, retention of nitrogenous waste products and/or dysregulation of extracellular volume and electrolytes.

Diagnosis

Anuria (,0,2 ml/kg/h) or Oliguria (<0.5ml/kg/h for 6 hours) OR increasing creatinine (>0.3 mg/dL above baseline)

Classification of AKI

• Pre-renal: reduced renal perfusion
• Renal: structural damage to the renal parenchyma
• Post-renal: obstruction to urinary outflow

Causes of AKI

• Decreased intravascular volume
  • Dehydration
  • Severe diarrhoea and vomiting
  • Bleeding
  • Burns
  • Nephrotic sydnrome
• Peripheral vasodilatation
  • Septic shock
  • Anaphylaxis
• Decreased cardiac function
  • Heart failure

• Tubular injury (often acute tubular necrosis (ATN))
  • Prolonged hypoperfusion
  • Nephrotoxins
  • Infections ( Malaria)
  • Rhabdomyolysis, severe hemolysis
• Vascular
  
  • Hemolytic uremic syndrome (recent bloody diarrhea)
  • Vasculitidies (symptoms from other systems - lungs, brain, joints, skin)
• Interstitial
  • Interstitial nephritis (nephrotoxins, infections)
• Glomerular
  • Post-infectious GN, rapidly progressive GN (lupus, vascilitidies)

• Bilateral urinary tract obstruction
  • Renal calculi, neurogenic bladder, urethral valve, spinal trauma/ tumours

Important points on examination

Pre-renal problem

• Tachycardia
• Weak pulses
• Poorly perfused peripheries
• Pallor
• Hypotension

Intrinsic renal problem

• Evidence of fluid overload (normal or raised BP, raised JVP, gallop rhythm)
• Rash (Henoch Schönlein Purpura, HIV)
• History of nephrotoxic medications, previous infections, bloody diarrhea, symptoms of autoimmune disease

Post-renal problem

• Large palpable bladder
• Obvious spinal lesion
• Neurological deficit

Investigations

• Blood pressure
• Urine dipstick
  Normal: prerenal and postrenal AKI
  Specific gravity: High in prerenal disease, low in ATN
• Urine microscopy
  Red cell casts: glomerulonephritis
  Granular or epithelial cell casts: ATN
  White cell casts: Interstitial nephritis or pyelonephritis
• FBC
• Creatinine
  Normal values: Newborn 0.3-1mg/dL, Infant 0.2-0.4mg/dL, Child 0.3-0.7mg/dL, Adolescent 0.5-1mg/dL
• K, Na, blood gases, if possible
• HIV
• Hepatitis B and C
• Renal ultrasound (especially rule out hydronephrosis and check kidney size)
• Peripheral blood film (fragmentation hemolysis in HUS)
• ECG, if K not available or hyperkalemic
• Echo + chest X-ray, if underlying chronic kidney disease is suspected (LVH?)

Management

• Admit
• Careful monitoring of blood pressure, urine output, fluid balance (input and output), weight - Strict fluid chart, see below
• Urinary catheter
• Optimize fluid balance
• Avoid nephrotoxins (NSAIDs, gentamycin, tenofovir)
• Treat the underlying cause (sepsis, malaria)

Pre-renal failure

• If the child is in hypovolaemic shock and /or severely dehydrated, give a fluid bolus of 10 ml/kg of normosaline rapidly. Repeat if necessary
• Continue fluid resuscitation following Plan C. Reassess regularly until euvolemic.
• Thereafter maintain careful fluid balance
• When euvolemic state is gained or patient has developed fluid overload, try Furosemide 1-2mg/kg bolus and consider regular furosemide, if the child is oliguric.

Intrinsic acute renal failure

• As above
• Treat possible hypertension with
  • Calcium channel blockers: Nifedipine initial dose 0.25-0.5mg/kg divided in 2 doses/day, titrate upwards up to 3mg/kg over 7-14 days
  • and if needed with Betablockers: Atenolol initial dose 0.5-1mg/kg/day and titrate up to 2mg/day
• Treat fluid overload with salt restriction and frusemide (start with 1 mg/kg OD)
• Consider steroids (Prednisolon 2mg/kg)
  • talk to senior
  • In severe poststreptococcal GN, interstitial nephritis, rapidly progressive GN

Post-renal failure

• Urgent catheterization
• Surgical consultation

For all types of acute renal failure

• Avoid nephrotoxins
• Adjust the doses of renally excreted drugs (penicillin, amoxicillin, cotrimoxazole, ciprofloxacin)
• Nutrition
  • Low salt diet
  • Low potassium diet (no bananas, tomatoes, unboiled potatoes, citrus fruits)
  • High caloric diet
  • Breastfeeding can be continued
• Consider Dialysis, if the child is not improving
  • Indications: Hyperkalemia, Acidosis, Severe fluid overload, Uremic symptoms (nausea, vomiting, confusion, convulsions)

Monitoring

Example of fluid balance chart - can be drawn out by hand

Complications

• Hyperkalemia with cardiac arrhythmias
• Acidosis - no clear guidelines of sodium bicarbonate, but it can be considered in severe metabolic acidosis (pH < 7,0) (1-2mEq/kg/dose iv)
• Hypocalcemia. IV-calcium in severe symptomatic hypocalcemia (arpopedal spasm, tetany, seizures). Give Calcium gluconate 10% (940mg/10 ml = 2,1 mmol) 20mg/kg (=0,2ml/kg) diluted 1:1 with Normale saline over 10-15 minutes. Can be given 1-2 times/day). Do not run faster than 4 ml of this solution (0,45 mmol Calcium) per minute
• Hypertension treatment as above

When to discharge

• Children can be discharged when they are passing normal volumes of urine and are able to eat and drink freely.

Follow-up

• Follow-up can be arranged in renal clinic (every second and last Thursday of the month)
• All children who have had acute kidney injury should be followed until they are normotensive without medications and creatinine is normal.