Acute Kidney Injury Flashcards
What is acute kidney injury?
Reduction in renal function following damage to the kidneys
Is acute kidney injury reversible or irreversible?
Reversible usually
What are risk factors for acute kidney injury?
- Chronic kidney disease
- Heart failure
- Diabetes
- Liver disease
- Older age (above 65 years)
- Cognitive impairment
- Nephrotoxic medications such as NSAIDS and ACE inhibitors
- Use of a contrast medium such as during CT scans
What drugs are a risk for acute kidney injury?
Nephrotoxic drugs- ACE inhibitors and NSAID’s
How many stages of AKI are there?
Three
What are the characteristics of stage 1 AKI?
- Creatinine increased by at least 1.5x baseline
- Rise in creatinine by more than 26µmol/L in the last 48 hours
- Urine output can be normal or less than 0.5ml/kg/hr for 6-12 hours
What are the characteristics of stage 2 AKI?
- Creatinine increased by 2-2.9x baseline
* Urine output less than 0.5/ml/kg/hr for more than 12 hours
What are the characteristics of stage 3 AKI?
- Creatinine increased by 3x baseline
* Urine output less than 0.3ml/kg/hr for more than 24 hours
What are the causes of AKI divided into?
Pre-renal
Renal
Post-renal
What are pre-renal causes of AKI due to?
Ischaemia or lack of blood flow to the kidneys
What are the pre-renal causes of AKI?
- Heart failure or liver failure
- Hypovolaemia- haemorrhage
- Renal artery stenosis
What will improve kidney function if the cause is pre-renal?
Restore perfusion to the kidneys
What are the renal causes of AKI due to?
Intrinsic damage to the glomeruli, renal tubules or interstitium of the kidneys
What are the renal causes of AKI?
- glomerulonephritis
- acute tubular necrosis (ATN)
- acute interstitial nephritis (AIN),
- drugs
What drugs can cause AKI?
NSAID’s
ACEi
What are the post-renal causes of AKI due to?
Problems after the kidneys, where there is an obstruction to the urine coming from the kidneys resulting in things ‘backing-up’ and affecting the normal renal function
What are post renal causes of AKI?
- kidney stone in ureter or bladder
- benign prostatic hyperplasia
- external compression of the ureter
What is the most common cause of AKI?
Acute tubular necrosis?
What is acute tubular necrosis?
Necrosis of renal tubular epithelial cells affects the functioning of the kidney.
Is acute tubular necrosis reversible?
In the early stages it is reversible if the cause if removed.
What are the 2 main causes of Acute tubular necrosis?
Ischaemia
Nephrotoxins
What is the ischaemic cause of Acute tubular necrosis?
Sepsis
Shock
What are the nephrotoxic causes of acute tubular necrosis?
Aminoglycosides
Rhabdomyolysis
Radiocontrast agents
Lead
What are the main features of acute tubular necrosis
Features of AKI: raised urea, creatinine, potassium
Muddy brown casts in the urine
What would you find in the urine of someone with acute tubular necrosis?
Muddy brown casts
Who does rhabdomyolysis occur in?
Typically in an elderly person who has fallen and doesn’t move for a few days
What is rhabdomyolysis also known as?
Long lie
What is rhabdomyolysis due to?
Prolonged immobility leads to rapid muscle breakdown
There is therefore an EXTREMELY high serum creatine kinase
What is the diagnostic level of creatinine in rhabdomyolysis?
Creatinine over 400 µmol/l indicated end stage renal failure and no past medical history
What are the features of rhabdomyolysis?
- acute kidney injury with disproportionately raised creatinine
- elevated creatine kinase (CK)
- myoglobinuria
- hypocalcaemia (myoglobin binds calcium)
- elevated phosphate (released from myocytes)
- hyperkalaemia (may develop before renal failure)
- metabolic acidosis
What are possible causes of rhabdomyolysis?
- seizure
- collapse/coma (e.g. elderly patients collapses at home, found 8 hours later)
- ecstasy
- crush injury
- McArdle’s syndrome
- drugs: statins (especially if co-prescribed with clarithromycin
What is the most common cause of rhabdomyolysis?
Elderly person that has fallen and not moved for hours
What is the management of rhabdomyolysis?
- IV fluids to maintain good urine output
* urinary alkalinization is sometimes used
Which medications should be stopped as they can worsen renal funciton?
- NSAIDs
- Aminoglycosides
- Angiotensin 2 receptor antagonists/ ARB
- Metaformin
- ACE inhibitors
- Naproxen
When should you stop metformin?
When AKI eGFR less than 45ml/min
What is the management of AKI?
Fluid rehydration with IV fluids in pre-renal AKI
Stop nephrotoxic medication-NSAIDS and antihypertensives that reduce the filtration pressure (i.e. ACE inhibitors)
Relieve obstruction in a post-renal AKI- insert a catheter for a patient in retention from an enlarged prostate
What is a differential of an AKI?
Dehydration
How can an AKI be differentiated from dehydraiton?
Creatinine isn’t as raised as the urea- urea will be high
Urea will be raised more in dehydration than the creatinine
What are classed as nephrotoxic drugs?
ACE inhibitors
ARBs
NSAIDs
Diuretics (furosemide)
What other medication might you need to stop in someone with an AKI?
Lithium
Why might you need you stop lithium in someone with an AKI?
Due to increased risk of toxicity- it is excreted by the kidneys
What does a lack of protein in the urine rule out?
Pre-renal and Post renal (damage is in the kidneys)
What can differentiate acute interstitial nephritis from acute tubular necrosis?
The WCC will be higher in someone with acute interstital nephritis as it is an inflammatory process
