Acute Renal Failure (ARF) and Kidney Injury Flashcards
What is Acute Kidney Injury/Renal Failure?
A sudden deterioration in kidney function
What are the defining clinical features of AKI?
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
What is the AKIN criteria?
Classifies AKI by serum creatinine/urine output
What are the changes in Stage 1 AKI?
Serum Creatinine - 150-200% increase OR 25umol/l increase in 48h
Urine Output - <0.5ml/kg/hr for 6 h
What are the changes in Stage 2 AKI?
Serum Creatinine - 200-300% increase
Urine Output - <0.5ml/kg/hr for 12 h
What are the changes in Stage 3 AKI?
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
In what patients is AKI more common?
Men
Elderly
Pre-existing CKD
How does AKI present?
Often asymptomatic w/ oliguria (<0.5ml/kg/h)
What are the potential complications of AKI?
Uraemia (vomiting, pruritis, pericarditis, encephalitis)
Hyperkalaemia
Pulmonary oedema due to fluid overload
What are the common pre-renal causes of AKI?
SHOCK - hypovolemic, cardiogenic, distributive
RENOVASCULAR OBSTRUCTION - embolus, aortic dissection, renal artery stenosis/thrombosis
What are the common post-renal causes of AKI?
Ureteric obstruction
Bladder outlet obstruction
What are the common intrinsic (renal) causes of AKI?
Acute tubular necrosis (85%) Interstitial nephritis (10%) Glomerular disease (5%)
What are the pharmaceutical causes of ATN?
Aminoglycosides
Cephalosporins
Contrast material
NSAIDs
What are the toxic causes of ATN?
Heavy metal poisoning
Myoglobinuria
Haemolytic Uraemic syndrome
Describe interstitial nephritis
Commonly caused by drugs (a/b)
Damage to tubular cells + interstitium
Managed w/ withdrawal of drugs & oral steroids
What is acute tubular necrosis?
Prolonged ischaemia leads to necrosis of cells lining renal tubules
- tubular membranes become porous
- tubules blocked by necrosed cells
What are the urine abnormalities in initial pre-renal AKI?
Urine osmolality high (>500mosmol/kg)
Urine Na low
What are the urine abnormalities in ATN?
Urine isotonic (<400mosmol/kg) Urine Na high
What is myoglobinuria?
Excess myoglobin in the urine
- very dark urine
- can damage tubules
What cause myoglobinuria?
Rhabdomyolysis
-muscle breakdown from trauma, strenuous exercise or medications
What is Haemolytic Uraemic Syndrome?
Syndrome of
- thrombocytopenia
- haemolysis
- ATN
What causes HUS?
Post diarrhoeal in children (E.coli O157)
Post URTI in adults
What are the management options for HUS?
Supportive
Dialysis
What is the prognosis of HUS?
Children - recover w/i wks
Adults - poor
What is the general approach to a patient w/ oliguria, or other signs of decreased renal function?
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)
What are the appropriate initial investigations in decreased renal function?
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
What investigations comprise a nephritic screen?
ANCA & anti-GBM (RPGN) ANA, dsDNA & complement (SLE) Immunoglobulins, serum electrophoresis (myeloma) Rheumatoid factor (RAGN) Hep B/C (MCGN) ASO (post-strep)
What are the immediate management options for an AKI?
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
What are the potential life threatening complications of AKI?
Refractory hyperkalaemia Pulmonary oedema Acidosis Uraemic pericarditis/encephalopathy Complete anuria Drug OD
Describe the natural history of an improving AKI
1 wk oliguria –> improving AKI –> 1wk polyuria –> normal kidney function (wk3)
What are the common electrolyte abnormalities in AKI?
Rapidly progressive uraemia Hyperkalaemia Hypernatremia (unless pre-renal) Metabolic acidosis Hypocalcaemia/hypophosphatemia (CKD)
What are the sx of rapidly progressive uraemia?
Anorexia Vomiting Pruritis Encephalopathy (confusion, drowsiness, fitting) Haemorrhagic episodes
What are the causes of hyperkalaemia?
Pseudohyperkalaemia AKI/CKD Drugs Acidosis Addison's Tumour-lysis syndrome Burns
What are the causes of pseudohyperkalaemia?
Haemolysis
Incorrect order of blood draw
Sample taken from drip arm
What are the drug causes of hyperkalaemia?
Supplements
K sparing diuretics
ACEIs
NSAIDs
What are the signs of hyperkalaemia on ECG?
Tall peaked T-waves
Widened QRS complex
Flattened P waves/prolonged PR
What are the complications of untreated hyperkalaemia?
Ventricular fibrillation
Ventricular tachycardia
What are the three management aims when treating hyperkalaemia?
Stabilise myocardium (calcium gluconate) Drive K intracellularly/buy time (insulin & dextrose/SABA) Remove K from body
When should emergency management of hyperkalaemia be initiated?
If K+ >6.5mmol/L or ECG changes
What is the emergency management of hyperkalaemia?
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
What long term management options are available for hyperkalaemia?
Calcium resonium (orally/rectally) Treat underlying cause
