Acute Renal Failure (ARF) and Kidney Injury

Question 1

What is Acute Kidney Injury/Renal Failure?

Answer 1

A sudden deterioration in kidney function

Question 2

What are the defining clinical features of AKI?

Answer 2

ANY OF:
Urine output <0.5ml/kg/hr for 6 hours
>50% rise in creatinine over 7 days
>26umol rise in creatinine over 48 hours

Question 3

What is the AKIN criteria?

Answer 3

Classifies AKI by serum creatinine/urine output

Question 4

What are the changes in Stage 1 AKI?

Answer 4

Serum Creatinine - 150-200% increase OR 25umol/l increase in 48h
Urine Output - <0.5ml/kg/hr for 6 h

Question 5

What are the changes in Stage 2 AKI?

Answer 5

Serum Creatinine - 200-300% increase

Urine Output - <0.5ml/kg/hr for 12 h

Question 6

What are the changes in Stage 3 AKI?

Answer 6

Serum Creatinine - >300% increase OR >350umol/L w/ acute rise of >45umol in 48 h
Urine Output - <0.3ml/kg/hr for 24h OR anuria for 12h

Question 7

In what patients is AKI more common?

Answer 7

Men
Elderly
Pre-existing CKD

Question 8

How does AKI present?

Answer 8

Often asymptomatic w/ oliguria (<0.5ml/kg/h)

Question 9

What are the potential complications of AKI?

Answer 9

Uraemia (vomiting, pruritis, pericarditis, encephalitis)
Hyperkalaemia
Pulmonary oedema due to fluid overload

Question 10

What are the common pre-renal causes of AKI?

Answer 10

SHOCK - hypovolemic, cardiogenic, distributive

RENOVASCULAR OBSTRUCTION - embolus, aortic dissection, renal artery stenosis/thrombosis

Question 11

What are the common post-renal causes of AKI?

Answer 11

Ureteric obstruction

Bladder outlet obstruction

Question 12

What are the common intrinsic (renal) causes of AKI?

Answer 12

Acute tubular necrosis (85%)
Interstitial nephritis (10%)
Glomerular disease (5%)

Question 13

What are the pharmaceutical causes of ATN?

Answer 13

Aminoglycosides
Cephalosporins
Contrast material
NSAIDs

Question 14

What are the toxic causes of ATN?

Answer 14

Heavy metal poisoning
Myoglobinuria
Haemolytic Uraemic syndrome

Question 15

Describe interstitial nephritis

Answer 15

Commonly caused by drugs (a/b)
Damage to tubular cells + interstitium
Managed w/ withdrawal of drugs & oral steroids

Question 16

What is acute tubular necrosis?

Answer 16

Prolonged ischaemia leads to necrosis of cells lining renal tubules

• tubular membranes become porous
• tubules blocked by necrosed cells

Question 17

What are the urine abnormalities in initial pre-renal AKI?

Answer 17

Urine osmolality high (>500mosmol/kg)

Urine Na low

Question 18

What are the urine abnormalities in ATN?

Answer 18

Urine isotonic (<400mosmol/kg)
Urine Na high

Question 19

What is myoglobinuria?

Answer 19

Excess myoglobin in the urine

• very dark urine
• can damage tubules

Question 20

What cause myoglobinuria?

Answer 20

Rhabdomyolysis

-muscle breakdown from trauma, strenuous exercise or medications

Question 21

What is Haemolytic Uraemic Syndrome?

Answer 21

Syndrome of

• thrombocytopenia
• haemolysis
• ATN

Question 22

What causes HUS?

Answer 22

Post diarrhoeal in children (E.coli O157)

Post URTI in adults

Question 23

What are the management options for HUS?

Answer 23

Supportive

Dialysis

Question 24

What is the prognosis of HUS?

Answer 24

Children - recover w/i wks

Adults - poor

Question 25

What is the general approach to a patient w/ oliguria, or other signs of decreased renal function?

Answer 25

Is it AKI/CKD? -CKD if comorbidities/long duration of sx If AKI is it pre/intrinsic/post -pre-renal (?shock ?renal bruits ?vasc pathology) -intrinsic (drug hx ?recent infec ?blood/protein in urine) -post-renal (abdo USS ?prostate)

Question 26

What are the appropriate initial investigations in decreased renal function?

Answer 26

``` Obs - hypo if pre-renal, hyper if CKD Exam - palpable bladder if obstruction Bloods - FBC, U&Es, bicarb, phos, CRP, clotting, CK Nephritic screen ABG Urine dip & MCS ECG/echo Renal USS +/- biopsy Non-contrast CT ```

Question 27

What investigations comprise a nephritic screen?

Answer 27

``` ANCA & anti-GBM (RPGN) ANA, dsDNA & complement (SLE) Immunoglobulins, serum electrophoresis (myeloma) Rheumatoid factor (RAGN) Hep B/C (MCGN) ASO (post-strep) ```

Question 28

What are the immediate management options for an AKI?

Answer 28

``` A-E resus Halt damaging drugs (ACEIs, NSAIDs) Restrict K+ intake Pre-renal --> treat shock Post-renal --> refer to urology Renal --> fluid balance, CVP measurement Management of complications Acute dialysis ```

Question 29

What are the potential life threatening complications of AKI?

Answer 29

``` Refractory hyperkalaemia Pulmonary oedema Acidosis Uraemic pericarditis/encephalopathy Complete anuria Drug OD ```

Question 30

Describe the natural history of an improving AKI

Answer 30

1 wk oliguria --> improving AKI --> 1wk polyuria --> normal kidney function (wk3)

Question 31

What are the common electrolyte abnormalities in AKI?

Answer 31

``` Rapidly progressive uraemia Hyperkalaemia Hypernatremia (unless pre-renal) Metabolic acidosis Hypocalcaemia/hypophosphatemia (CKD) ```

Question 32

What are the sx of rapidly progressive uraemia?

Answer 32

``` Anorexia Vomiting Pruritis Encephalopathy (confusion, drowsiness, fitting) Haemorrhagic episodes ```

Question 33

What are the causes of hyperkalaemia?

Answer 33

``` Pseudohyperkalaemia AKI/CKD Drugs Acidosis Addison's Tumour-lysis syndrome Burns ```

Question 34

What are the causes of pseudohyperkalaemia?

Answer 34

Haemolysis Incorrect order of blood draw Sample taken from drip arm

Question 35

What are the drug causes of hyperkalaemia?

Answer 35

Supplements K sparing diuretics ACEIs NSAIDs

Question 36

What are the signs of hyperkalaemia on ECG?

Answer 36

Tall peaked T-waves Widened QRS complex Flattened P waves/prolonged PR

Question 37

What are the complications of untreated hyperkalaemia?

Answer 37

Ventricular fibrillation | Ventricular tachycardia

Question 38

What are the three management aims when treating hyperkalaemia?

Answer 38

``` Stabilise myocardium (calcium gluconate) Drive K intracellularly/buy time (insulin & dextrose/SABA) Remove K from body ```

Question 39

When should emergency management of hyperkalaemia be initiated?

Answer 39

If K+ >6.5mmol/L or ECG changes

Question 40

What is the emergency management of hyperkalaemia?

Answer 40

``` Continuous ECG monitoring 10ml of 10% calcium gluconate IV -repeat at 5mins, max 3 doses 125mg 20% dex + 10U actrapid, large vv over 30mins -50ml of 50% glucose w/ 10U actrapid Sodium bicarb (if pH <7.2) Consider 10mg Salbutamol neb ```

Question 41

What long term management options are available for hyperkalaemia?

Answer 41

``` Calcium resonium (orally/rectally) Treat underlying cause ```