Acute Renal Failure (Diagnosis Approach and Management

8/12/2019 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



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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


Malaysian Paediatric Protocol 3rdEdition

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Acute Renal Failure (Diagnosis Approach and Management