Renal failure

Question 1

Investigations

Answer 1

Proteinuria or microscopic haematuria with casts suggest primary renal insult

Renal ultrasound always mandatory in anuric

Prerenal from Intrinsic
Prerenal has good concentrating ability making urine with high osmolarity and high urea, as well as low sodium concentration

ATN has low osmolar urine with high sodium and low sodium urea/creatinine

If kidneys are small with echo bright parenchyma –> suggests chronic damage

Sometimes echo bright due to oedema

Question 2

Rhabdo

Answer 2

Crush injury, acute limb ischaemia, prolonged surgery or immobility

Test for myoglobin

Need to aggressively volume expand and give sodium bicarbonate to alkalinise the urine
Also need to diurese and limit negative effect of acid breakdown products of myoglobin on renal tubules

Question 3

Indications for RRT

Answer 3

Absolute
Refractive high K
Refractory pulmonary oedema
Uraemic encephalopathy

Relative
Acidosis
Uraemia
Pericarditis
Toxin removal

Question 4

Haemodialysis

Answer 4

Uses LMW solute between blood and diayslate compartment separated by semi permeable membrane
Solute waste moves down concentration gradient

Intermittent –> rapid changes in plasma osmolality and volume, continuous better in critically ill

Question 5

Haemofiltrates

Answer 5

Continuous convection of molecules across a permeable membrane

Fluid removed is replacement with buffered physiological solution

More effective at removing large quantities of fluid, but not as effective as dialysis at clearing smaller molecules

CVVH usually

This is because least risk of significant IV fluid shifts and HD instability

Rise above 35mmol in urea unresponsive to other therapies absolute indication for CRRT

Question 6

Pulmonary oedema

Answer 6

Hi flow
IV diamorphine --> vasodilatory and anxiolytic
IV GTN infusion
IV furosemide
Higher level of support
CPAP