Acute Kidney Injury Flashcards
Define acute kidney injury
An abrupt (<48hours) reduction in kidney function defined as;
- an absolute increase in serum creatinine by >26.4
- increase in serum creatinine by >50%
- reduction in urinary output
Describe stage 1 AKI
Serum creatinine - >26 or >1.5-1.9 times the reference baseline creatinine
Urine output <0.5ml/kg/hour for >6 hours
Describe stage 2 AKI
Serum creatinine >2-2.9 times the reference
Urine output <0.5ml/kg/hour for >12 hours
Describe stage 3 AKI
Increased creatinine >3 times reference or >354 or need for RRT
Urine output <0.3ml/kg/hour for >24 horus or 12 hours of anuria
State the risk factors for AKI
- Older age
- CKD
- Liver Disease
- PVD
- Diabetes
- Previous AKI
- Cardiac Failure
- Hypotension/hypovolaemia
- Sepsis
- Recent contrast
- Deteriorating NEWS
- Medications
What are the pre-renal causes of AKI?
Hypovolaemia
Hypotension
Hyperfusion
What causes hypovolaemia leading to AKI?
Haemorrhage
Volume depletion through burns or diarrhoea/vomitting
What causes hypotension leading to AKI?
MI - cardiogenic shock
Distributive shock - sepsis or anaphylaxis
What causes hypo-perfusion leading to AKI?
NSAIDs, COX2 inhibitors, ACEi, ARB, hepatorenal syndrome
State normal urine output
0.5ml/kg/hour
Define oliguria
<0.5ml/kg/hour
If decreased perfusion occurs how does the body normally cope?
Renin is released and this causes angiotensin II to cause vasoconstriction and GFR is maintained
How do ACEi impact the body’s ability to compensate for hypo-perfusion?
ACEi reduce angiotensin II which leads to a reduced GFR which is normal ok but if the patient loses a significant amount of fluid there will be a major fall in GFR
If left untreated what can pre-renal AKI lead to?
Acute Tubular Necrosis
What is the treatment for pre-renal AKI?
Assess hydration - BP, HR, JVP, Cap refil, oedema
Fluid challenge - 0.9% NaCl if no improvement after 1000ml then get help
What causes renal AKI?
Small Vessel Vasculitis
Glomerulonephritis
Interstitial Nephritis
Tubular Injury
What causes interstitial nephritis?
Drugs - antibiotics, PPIs, NSAIDs
Infection -TB
Systemic disease - sarcoidosis
What causes tubular injury?
Ischaemia, drugs, contrast, rhabdomylosis
Describe rhabdomyolosis
Breakdown of damaged skeletal muscles leading to the release of myoglobin in the blood
What are the signs/symptoms of renal AKI?
Nausea/vomiting, fluid overload, itch, constitutional symptoms, hypertension, effusions, oliguria, uraemia
Name some clues that might help to diagnose renal AKI
- signs of infection/systemic disease
- drug chart
- urinalysis
- recent contrast
- blood results
- vascular bruits
What are vascular bruits a sign of?
Renal Artery Stenosis
What investigations are carried out in AKI?
U and E - particularly potassium
FBC and coagulation - HUS, disseminated clotting
Urinalysis - glomerulonephritis/vasculitis
USS - size/obstruction
Immunology
Protein electrophoresis and BJP -myeloma >50yo
How is renal AKI treated?
Establish good perfusion with fluid
Inotropes/vasopressors
Treat underlying cause
Stop nephrotoxic drugs
What are the complications of renal AKI?
Hyperkalaemia, fluid overload, severe acidosis , uraemia pericardial effusion, severe uraemia
What causes post renal AKI?
Obstruction of urine flow leading to back pressure - hydronephrosis and loss of concentrating ability
What can obstruct the urine flow?
Stones, cancer, strictures, extrinsic pressure
How is post renal AKI diagnosed?
US and CT show dilated renal pelvis
How is post renal AKI treated?
Catheter and nephrostomy, refer to urology
State the values for normal, hyperkalaemia and life threatening potassium levels
Normal <3.5-5
Hyperkalaemia >5.5
Life threatening >6.5
What are the effects of increased potassium?
Cardiac arrhythmia and muscle weakness/tingling
What are the key signs of hyperkalaemia on ECG?
Peaked T waves, prolonged QRS, eventually becomes a sine wave and can lead to VT/VF
How is hyperkalaemia treated?
Protect myocardium - calcium gluconate 10mls 10%
Move potassium back into cells - insulin with dextrose and salbutamol nebuliser
Prevent GI absorption (not in acute setting) - calcium resonium
What indicates urgent haemodialysis?
Acidosis
Electrolyte disturbance (potassium >7 or >6.5 and unresponsive to treatment)
Intoxication
Overload of volume (not passing urine or response to diuretics)
Uraemia >40, pericardial rub or effusion
What causes acute tubular necrosis?
Ischaemia
Nephrotoxins
Sepsis
What will be present in the urine of patients with acute tubular necrosis?
Muddy brown casts due to necrotic epithelium
High urinary sodium
How will interstitial nephritis present?
Temperature, rash, eosinophilia, white cell casts
How is interstitial nephritis treated?
Prednisolone
What drugs must be stopped in AKI?
NSAIDs
ACEi/ARB
Diuretics
Aminoglycosides
What drugs should you consider stopping in AKI?
Metformin
Lithium
Digoxin
