AKI Flashcards
How do you define an AKI?
Rise in serum creatinine (compare to baseline)
Oliguria or Anuria being less than 0.5ml/kg/hr for at least 6 hours
What is an AKI?
Sudden deterioration in renal function over hours or days
What are the 2 ways you can classify AKIs?
Serum creatinine or Urine output
What are the classifications for AKIs using serum creatinine?
Stage 1 = x1.5 - 1.9 times the baseline serum creatinine
Stage 2 = x2 - 2.9 times the baseline serum creatinine
Stage 3 = x3 and above the baseline serum creatinine
What are the stages of AKI using urine output as the grading system?
Stage 1 = <0.5ml/kg/hr for 6-12hrs
Stage 2 = <0.5ml/kg/hr for > 12hrs
Stage 3 = <0.3ml/kg/hr for 24hrs or more OR ANURIA 12hrs or more
What are the 3 classes of cause of AKI?
Pre-renal
Renal
Post-renal
What are some pre-renal causes of AKI?
Sepsis
Hypovolaemia
Shock
Renal artery stenosis
Medications
Heart failure
What are some medications that can cause an AKI?
And what type of cause of AKI are they?
NSAIDs (Pre renal)
ACEi (Pre renal)
Gentamicin (Renal)
Loop diuretics (Pre renal)
How do NSAIDs cause an AKI?
COX enzymes responsible for producing prostaglandins which are responsible for vasodilation of the afferent arteriole
If they are inhibited, this leads to renal hypoperfusion leading to reduced GFR
How can ACE inhibitors cause an AKI?
ACE enzymes responsible for leading to the end production of Angiotensin II which is a vasoconstrictor (so leads to VASOCONSTRICTION of efferent arteriole)
If inhibited, leads to vasodilation of the efferent arteriole leading to reduced GFR and so an AKI
What are some renal causes of AKI?
Acute tubular necrosis
Acute interstitial nephritis
Glomerularnephritis
Vasculitis
Haemolytic Uraemic Syndrome
Rhabdomyolysis
Drugs directly nephrotoxic
SLE (lupus nephritis)
What is Acute Tubular Necrosis and where in the kidney does it most commonly affect and why?
Necrosis of the epithelial cells of the renal tubules
PCT since has very high O2/metabolic demand and comes into contact with the most nephrotoxic substances
What can cause Acute Tubular Necrosis?
Ischaemia due to hypoperfusion (Pre-renal)
Nephrotoxins like gentamicin, radiocontrast agents or cisplatin (renal)
What can be seen on urinalysis with acute tubular necrosis?
Muddy brown casts
May see renal tubular epithelial cells
Is acute tubular necrosis reversible?
Yes
1-3 weeks
What this Acute Interstitial Nephritis?
Cause or renal AKI
Acute inflammation of interstitium (space between tubules and vessels) caused by an immune reaction
What are some causes of Acute Interstitial Nephritis?
Immune reactions with:
-Drugs (NSAIDs or Abx)
-Infections (E.coli or HIV)
-Autoimmune (sarcoidosis or SLE)
How do you treat Acute Intersistial Nephritis?
Treat underlying cause
Steroids can help reduce inflammtion
What are some features associated with an AKI?
Rash
Fever
Flank pain
Eosinophilia
Hyperkalaemia
Metabolic acidosis
Fluid overload
Uraemia
What are some post renal causes of AKI?
Obstruction to outflow of urine leading to back pressure in kidney
-kidney stones
-tumours
-strictures (ureteric/urethral)
-bilateral calculi
-BPH
-Neurogenic bladder
-retroperitoneal fibrosis
How would you investigate a patient with a potential AKI??
FBC
Urinalysis/Urine dip
U+Es
VBG
Creatine kinase (?Rhabdomyolysis)
ECG (K+ levels)
MC+S of urine
What imaging would you request for a patient with an AKI?
ECG
USS KUB if post renal suspected
CT KUB non contrast if USS is inconclusive
Bladder scan
CXR
Why may you want to do a CXR for a patient with ?AKI?
Pulmonary oedema
Heart failure
Source of infection
Resp involvement
Complications of treatment monitoring (ARDS or fluid overload)
How do you prevent an AKI?
Avoid nephrotoxic medications
Ensure adequate fluid intake
Additional fluids with radiocontrast agents
How do you manage an AKI?
Depends on cause
IV fluids (dehydration and hypovolaemia)
Stop meds that may worsen (NSAIDs ACEi)
Withhold/adjust meds that may accumulate with poor GFR
Relieve obstruction (catheter)
Dialysis (if severe)
When do you require a renal specialist when a patient has an AKI?
Severe AKI
Doubt about cause
Complications s
What are the complications of AKI?
Fluid overload
Heart failure
Pulmonary oedema
Hyperkalaemia
Metabolic acidosis
Uraemia (encephalopathy and pericarditi)
What is your IMMEDIATE action if you suspect a post renal cause of AKI (obstruction)?
Imaging:
CT KUB non contrast
Ideally want US KUB first if available
What is your immediate acute management if patient is in retention due to post renal caused AKI ?
Relief with catheter
Broadly, what causes a pre-renal AKI?
Hypoperfusion of the kidneys
What are some causes of hypovolaemia leading to a pre renal AKI?
Dehydration
GI losses (Vomiting and Diarrohoea)
Blood loss (overt =. Outside of body Covert = retroperitoneal, femoral fracture)
Bowel obstruction
Burns
Heatstroke
3rd spacing (when too much fluid enters interstitial space)
What is your IMMEDIATE action/assessment when you suspect a pre-renal AKI?
Fluid assessment
What is the IMMEDIATE action if you think a patient might have a renal cause / glomerulonephritis as a cause of their AKI?
Urine dip
What would a urine dip indicating potential glomerulonephritis reveal?
+ve erythrocytes (Haematuria)
+ve protein (proteinuria)
Why do you not want to catheterise all patients with an AKI if it can be helped?
Traumatic catheterisation may introduce blood into the urine
So when urine dipping it’s impossible to know whether the blood is coming from a very serious Glomerulonephritis or the Catheter insertion
What drug is given as the acute management to treat alcohol poisoning or ethylene glycol poisoning (anti-freeze)?
Fomepizole
What drug is given as the acute management to treat alcohol poisoning or ethylene glycol poisoning (anti-freeze)?
Fomepizole
