Acute Renal Failure Management and Investigation

*Avoid giving Ibuprofen

• Patient Weight – Required Daily
  
• Urine Output
• Blood Pressure
• Hydration Status
• Blood Biochemistry and FBC
• Cardiorespiratory Examination
• Neurological Examination
• Musculoskeletal Examination
• Bruising/Bleeding
• Drug History Investigations

Consider the following on clinical grounds

For calculation of FENa- http://www.mdcalc.com/fractional-excretion-of-sodium-fena/

Fluid Management

• Correction of Hypovolaemia
• Fluid Overload (Red Flag):
  • Furosemide 2 - 5mg/kg over 1 hour
  • Fluid restriction
  • Minimalise drug infusion volumes
  • Accurate input/output
  • Daily weight
  • Dialysis 
• Beware Polyuria 

Aim is to maintain isovolaemia erring on the side of minimal fluid overload.

As a rule of thumb, daily fluid requirements should equal insensible fluid losses plus output (urine, vomiting, drain losses, diarrhoea etc). Insensible fluid losses can be calculated as per the table below: 

Electrolyte Abnormalities

Hyponatraemia

• Salt loss > water loss 
  • Volume resuscitation
  • Sodium deficit (140-Na) x 0.65 x Body weight
  • Replace deficit with 0.9% saline, usual maintenance
• Water gain > Na
• Fluid restriction
• Hypertonic saline with loop diuretic
• Mannitol

Hypernatraemia

Hypernatraemia may be due to:

• Extrarenal fluid loss in PICU patients
• Excess sodium bicarbonate
• Volume resuscitation
• Water deficit 
  - weight x 0.65 x ((Actual Na/140)-1))
  - Replace with 0.45% saline over 36-72 hrs
• Central DI- DDAVP
• Nephrogenic DI- Diuretic therapy

Hypocalcaemia

• Emergency- 0.5ml/kg/hr of 10% Ca Gluconate
• 50ml/kg Ca/kg/day
• If resistant, check Mg

Hyperphosphataemia

• Phosphate restriction
• Phosphate binders e.g. Ca Carbonate

Hypophosphataemia

• Polyuric states

Hyperkalaemia

These are invariably acidosis and are often mixed respiratory and metabolic especially in the intensive care setting. Treatment is generally only indicated if there is associated hyperkalaemia or if the acidosis is profound. 

Treatment of Acid-Base Disorders

• Base Deficit (mmol) = Base Excess x Weight/3
• Replace half of the deficit initially
• Sodium Bicarbonate is hypertonic with a risk of CNS complications or hypernatraemia and is only effective with adequate ventilation.
• Rapid correction of acidosis may cause hypocalcaemia and tetany or seizures
• Therefore rapid correction to be avoided

Acute renal failure is a hypercatabolic state and requires aggressive nutritional support. Unlike adults there is no indication for dietary protein restriction, which should be delivered in amino acids or protein of high biological value. The majority of calories should however be delivered as carbohydrates. 

• Calories 1400 kcal/m2/day
• Protein 0.6g/kg/day (1.5g if dialysed)
• Intralipid - medium chain triglycerides
• Folate and Vitamin supplementation

May relate solely to salt and water overload and therefore in the presence of oligo/anuria and in the absence of hypovolaemia an initial trial of diuretic therapy is justified.

For further details of the management and investigation of hypertension – see appropriate protocol.

Drug therapy for the emergency treatment of hypertension is outlined below.