acute renal failure (diagnosis approach and management
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INVESTIGATIONS
Blood: Full blood count, Arterial blood gas, serum albumin,
Calcium ,Phosphate.
Urine: UFEME, Urinalysis
Renal function test: blood urea, electrolytes, creatinine.
Imaging: Renal ultrasound
Chest Xray
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TO DIFFERENTIATE PRE RENAL AND INTRINSIC RF
1) Fractional excretion of sodium[U/P Na U/P Creatinine] x 100
U= Urine concentration
P= Plasma concentration
2%= intrinsic renal dysfunction
Nelson Paediatric Textbook 6thEd.
2) Urine Chemical Profile
-Pre renal : Na40mEq/L
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URINALYSIS
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RENAL FUNCTION TEST
Serum BUSE
Hyperkalemia [serum K > 6.0 mmol/l
(neonates) and > 5.5 mmol/l (children] Hyponatremia [136-145mmol/L]
Hypocalcemia[9-11mg/dL]
Serum creatinine- 0.6-1.3mg/dL
Creatinine clearance75-125ml/min( decreases with age)
Blood Urea Nitrogen
- If elevated = AZOTEMIA
- 2 years= 5-20mg/dL
Hyponatremia is due to
dilutional disturbance ,
corrected by fluid restriction
Nelson Paediatric Textbook 6thEd.
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Acute Kidney Failure
Considerations
Volume status
Blood pressure status
Electrolyte abnormalities status
Acid Base status
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ManagementCONSERVATIVE AND SUPPORTIVE
Fluid resuscitation(30% of
maintenance)
Fluid bolus of isotonic saline (10-
20ml/kg/dose) with careful
hemodynamic monitoring
If fluid therapy adequate but oliguriapersists, give furosemide to convert to
non oliguric state
Monitor for fluid overload signs
(hypertension,raised JVP, basal
crepitations,hepatomegaly)
Medical Management
Hypertension
Electrolyte imbalance
Acid base imbalance
Paediatric Protocol 3rdEdition
If the child did not pass urine within 2 hours, a catheter/suprapubic tap has to
be done to assess if there is any urine formation. If the child has no urine
formation, CVP has to be monitored.
Post renal causes should be elicited and treated.
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Fluid Balance
In hypovolaemia:
- Fluid resuscitation regardless of oliguric or anuric state
- Give crystalloids, e.g. isotonic 0.9% saline/ Ringers lactate 20ml/kg fast(in
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In hypervolaemia:
Features of volume overload signs (hypertension,raised JVP, basal
crepitations,hepatomegaly)
- If necessary to give fluid, restrict to insensible loss (400ml/m2/day or30ml/kg in neonates depending on conditions)
- IV Frusemide 2mg/kg/dose9over 10-15minutes), maximum of
5mg/kg/dose.
- Dialysis if no response or if volume overload is life threatening
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Hypertension
Related to fluid overload or alteration in vascular tone.
Choice of anti hypertensive drugs depends on degree of BP elevation,
presence of CNS symptoms of hypertension and cause of renal failure.
A diuretic is usually needed.
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Electrolyte Abnormalities
Hyperkalaemia:
- serum K+ > 6.0mmol/L(neonates) and
> 5.5 mmol/L (children)
- cardiac toxicity develops when plasma potassium >7mmol/LHyperkalemia on ECG
1. Tall peak T waves k>6
2. Prolonged PR interval K>83. Widened QRS complex K>7
4. Flattened P wave K>9
5. Sine waves QRS complex merge with peaked T waves) K> 6-7
6. VF or asystole K> very high
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Hyponatraemia:
- Usually dilutional from fluid overload
- If asymptomatic, fluid restrict
- Dialyse if symptomatic or above measure fails
Hypocalcaemia:
- Treat if symptomatic(serum Ca2+ < 1.8mmol/L) and if sodium bicarbonateis required for hyperkalaemia, with IV 10% Calcium gluconate 0.5ml/kg, givenover 10-20 minutes, with ECG monitoring.
Hyperphosphataemia:
- Phosphate binders e.g. calcium carbonate or aluminium hydroxide orallywith main meals
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Acid Base Imbalance Mild metabolic acidosis is common in ARF as a result of retention of
hydrogen ions, phosphate, and sulfate, but it rarely requires treatment.
If acidosis is severe (arterial pH < 7.15; serum bicarbonate
< 8mEq/L) or contributes to hyperkalemia, treatment is required.
Correction of metabolic acidosis with intravenous sodium bicarbonatemay precipitate tetany in patients with renal failure as rapid correctionof acidosis reduces the ionized calcium concentration.
Ensure that patients serum calcium is >1.8mmol/L to preventhypocalcemic seizure with sodium bicarbonate therapy.
Bicarbonate deficit= 0.3x body weight(kg)x base excess
-replace the half of deficit with IV 8.4% sodium bicarbonate
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Indications for Dialysis
Volume overload with evidence of severe pulmonary edema andrefractory hypertension
Persistent hyperkalemia
Severe electrolyte abnormalities (Calcium/phosphorus imbalance,with hypocalcemic tetany, symptomatic hyponatraemia)
Severe metabolic acidosis unresponsive to medical therapy
Blood urea nitrogen > 100-150mg/dL
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Types of Dialysis
Intermittent hemodialysis:
- Useful in patients with relatively stable hemodynamic status.
- This highly efficient process accomplishes both fluid and electrolyteremoval in 34/hr sessions using a pump-driven extracorporeal circuit and
large central venous catheter.
- Intermittent hemodialysis may be performed three to seven times a week
based on the patient's fluid and electrolyte balance.
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Peritoneal dialysis:
- Most commonly employed in neonates and infants with ARF.
- Hyperosmolar dialysate is infused into the peritoneal cavity via a surgicallyor percutaneously placed peritoneal dialysis catheter.
- The fluid is allowed to dwell for 4560/min and is then drained from thepatient by gravity (manually or with the use of a cycler machine).
- Cycles are repeated for 824?hr/day based on the patient's fluid andelectrolyte balance; peritoneal dialysis is contraindicated in patients withabdominal disorders.
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Continuous renal replacement therapy :
- (CRRT) is useful in patients with unstable hemodynamic status,concomitant sepsis, or multiorgan failure in the intensive care setting.
- CRRT is an extracorporeal therapy in which fluid, electrolytes, and small-and medium-sized solutes are continuously removed from the blood(24hr/day) using a specialized pump-driven machine.
- Usually, a double-lumen catheter is placed into the subclavian, internal
jugular, or femoral vein.
- The patient is then connected to the pump-driven CRRT circuit, whichcontinuously passes the patient's blood across a highly permeable filter.
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CRRT
CVVHF
Continuos Veno-Venous Hemofiltration
CVVHD
Continuous Veno-Venous HemoDialysis
CVVHDF Continuous Veno-Venous HemoDiafiltration
(CVVH-D) utilizes the principle of diffusion by circulating dialysate in a
countercurrent direction on the ultrafiltrate side of the membrane. Noreplacement fluid is used.
Continuous hemodiafiltration (CVVH-DF) employs both replacement fluid
and dialysate, offering the most effective solute removal of all forms of
CRRT.
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CVVHD Circuit
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CVVHDF Circuit
H2OH2O
H2O
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Continuous Hemofiltration
Easy to use in PICU
Rapid electrolyte correction
Excellent solute clearances
Rapid acid/base correction
Controllable fluid balance
Tolerated by unstable pts.
Early use of TPN
Bedside vascular access
routine
Systemic anticoagulation
(except citrate)
Frequent filter clotting
Vascular access in infants
Advantages Disadvantages
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References
Nelson Paediatric Textbook 6thEd.
Malaysian Paediatric Protocol 3rdEdition