Acute Kidney Injury (Complete) Flashcards
Define acute kidney injury
Acute reduction in renal function
AKI is diagnosed using what criteria system?
KDIGO criteria
(Kidney Disease: Improving Global Outcomes)
According to KDIGO what criteria must be met to diagnose a patient with AKI?
Either one of the following:
1) Increase in serum creatinine by >26.5 mmol/l within 48 h
2) Increase in serum creatinine > 1.5x the baseline within the last 7 days
3) Urine output < 0.5 ml/kg/h for 6 hours
AKI causes can be divided into which 3 categories? What is the pathophysiology behind each category?
Pre-renal causes (Hypoperfusion and ischaemia)
Renal causes (Damage to the kidney itself)
Post-renal causes (Obstruction)
What category of causes most commonly lead to AKI
Pre-renal causes
Give 4 examples of pre-renal causes of AKI
Hypovolaemia
* Dehydration
* Haemorrhage
* Burns
* GI losses
Hypotension
* HF
* Sepsis
Medications
* NSAIDs
* ACE/ARB
* Diuretics
Renal artery stenosis
List 7 examples of renal causes of AKI
Glomerular diseases
* Acute glomerulonephritis
* Nephrotic syndrome
Tubular diseases
* Acute tubular necrosis
* Rhabdomyolysis
Interstitial diseases
* Acute interstitial nephritis (secondary to drugs)
Renal vessel diseases
* Renal vein thrombosis
* Vasculitis (e.g. haemolytic uraemic syndrome)
List examples of post-renal causes of AKI
Luminal
* Ureteric kidney stones
* Blocked catheter
Intramural
* Urethral/ureteric strictures
* Ureteric carcinomas
External compression
* Abdominal/pelvic tumor
* BPH
Are pre-renal, renal or post-renal causes the most common in AKI?
Pre-renal causes
Define acute glomerulonephritis
Acute inflammation of the glomeruli of the kidneys
Define acute tubular necrosis
Necrosis of the tubules of the nephrons of the kidney
Define interstitial nephritis
Inflammation of the interstitium (Space between the nephrons)
Define haemolytic uraemic syndrome
Syndrome which develops due to small vessels in the kidney become damaged or inflammed, resulting in small blood clot formation and hence occlusion.
What are the main risk factors for acute kidney injury (10)?
Aged 65 and over
CKD
Chronic diseases (e.g. DM, HF, liver failure)
Previous AKI
Nephrotoxic drugs within the past week
* NSAIDs
* ACE inhibitors/ARBs
* Diuretics
Conditions resulting in urinary obstruction (e.g. BPH)
Use of iodinated contrast agents within the past week
Malignancy
Renal transplant
Requires a carer e.g. disaibility or impairement: limited access to fluids because of reliance on a carer
List 5 examples of nephrotoxic drugs which can increase likelihood of developing an AKI.
NSAIDs
ACEi
ARBs
Diuretics
Aminoglycosides (type of broad-spectrum ABs -mycins/cins)
What is considered stage 1 AKI according to KDIGO?
Either of following:
1) Creatinine rise of 26 micromol/L or more within 48 hours
2) Creatinine rise to 1.5-1.99x baseline within 7 days
3) Urine output < 0.5 mL/kg/hour for more than 6 hours
What is considered stage 2 AKI according to KDIGO?
Either of following:
1) Creatinine rise to 2-2.99x baseline within 7 days
2) Urine output < than 0.5 mL/kg/hour for more than 12 hours
What is considered stage 3 AKI according to KDIGO?
Either of following:
1) Creatinine rise to 3x baseline or higher within 7 days
2) Creatinine rise to 354 micromol/L or more with either acute rise of > 26 micromol/L within 48 hours or _>_50% rise within 7 days
3) Urine output < than 0.3 mL/kg/hour for 24 hours
4) Anuria for 12 hours
What are the aetioligical manifestations of an AKI? (3)
Assymptomatic (picked up on bloods)
Oliguria
Increase in unexcreted waste products such as: Pottasium, urea, creatinine.
Fluid overload (due to osmotic gradient of unxecreted waste products)
What are the main signs/symptoms of acute kidney injury? (4)
Oliguria (<0.5ml/kh/hr)
Fluid overload
* Pulmonary oedema
* Peripheral oedema
* Raised JVP
Arrythmias (secondary to pottasium and acid-base dysregulation)
Features of uraemia
* Nausea and vomitting
* Fatigue
* Confusion (encephalopathy)
* Anorexia
* Pruritis
* Uraemic pericarditis
What findings on examination are suggestive of AKI?
BP changes
* Hypertension (complication of AKI)
* Hypotension (pre-renal cause of AKI)
Signs of fluid overload
* Pulmonary oedema
* Peripheral oedema
* Raised JVP
Bladder distention (due to urinary retention)
Pericardial rub (uraemic pericarditis)
What are the main investigations to order in patients suspected of AKI?
Bedside:
ECG (Check for arrythmia due to hyperkalaemia)
Urine dipstick/urinalysis (check for underlying causes)
Urine output monitoring (dont catheterise)
Bloods:
ABG (check for acidosis and allows rapid pottasium management)
FBC (check for infection)
CRP (check for infection/vasculitis)
U&Es (For diagnosis and to check for hyperkalaemia)
Creatinine kinase (Check for rhabdomyloysis)
LFTs (may be deranged in severe hypotension)
Clotting fators (establish baseline if renal biopsy needed [rare])
Bone screen (Check for hypercalcaemia due to myeloma)
Imaging:
Bladder scan (Check for urinary retention)
US KUB (If post-renal causes suspected)
CXR (pulmonary oedema)
Special test:
Glomerulonephritis screen if cause still unknown
Renal biopsy (if cause unknown even after specialist test)
What are the main findings on investigation can present in paients with AKI?
Elevated serum urea
Elevated serum creatinine
Hyperkalaemia
What findings may be seen from urine dipstick in patients with AKI?
Blood + protein (In cases of glomerular disease)
WBCs (In cases of infection or interstitial nephritis)
What ECG findings can show in patients with AKI? (4)
Signs of hyperkalaemia such as:
Peaked T-waves
Prolonged PR
Widened QRS
Atrial arrest
What findings on a FBC can present in AKI?
Leukocytosis (suggests infection cause such as sepsis)
Low platelets (Points towards haemolytic uraemic syndrome and other rare causes)
Anaemia (can present in AKI secondary to haemolytic uraemic syndrome, vasculitis, myeloma)
Why is ABG needed for patients with suspected AKI? What are two potential findings in ABGs in these patients?
Due to buildup of acidic waste products and reduced kidney function, patient at risk of a metabolic acidosis.
May also show hypoxia if person have oedema due to AKI.
Hypoxia and acidosis
Whys is a renal US useful in patients suspected of AKI? When should it be ordered?
Can observe renal size and check for conditions such as hydronephrosis indicating obstructive cause.
Order US within 24 hours if no identifiable cause for the deterioration or are at risk of urinary tract obstruction
What is the management plan for patients with AKI?
ABC approach: Sit up and oxygen if pulmonary oedema, IV fluids if hypovolaemic.
Suspend any nephrotoxic medications (e.g. NSAIDs, ACE, ARB, Diuretics, aminoglycosides)
Suspend renally excreted drugs: E.g. metformin, Digoxin [AF], lithium.
Continous monitoring: for fluid status, electrolytes and urine output.
Treat life threatening complications: E.g. sepsis, hyperkalaemia
Treat underlying causes:
Post-renal: IV fluids if hypovolaemic, IV ABs if sepsis
Intrinsic causes: Nephrology review
Post-renal causes: Catheterisation and urology review
In severe cases: Dialysis
What medication should be suspended due to increased risk of toxicity as a result of AKI
Renally excreted medication specifically
- Metformin
- Lithium
- Digoxin
What managemet options are available for patients with hyperkalaemia?
IV calcium gluconate (Stabilises cardiac membrane)
Combined insulin/dextrose infusion (Increases K+ intracellular uptake)
Nebulised salbutomol (Increases K+ intracellular uptake)
Calcium resonium (Increases K+ excretion)
Loop diuretic (Increases K+ excretion)
Dialysis (Increases K+ excretion)
What are the indications for dialysis in patients with acute kidney injury? (5)
AEIOU:
A: Acidosis (severe acidosis with pH less than 7.2)
E: Electrolyte imbalance (persistent hyperkalaemia)
I: Intoxication (poisoning)
O: Oedema (refractory pulmonary oedema)
U: Uraemia (encephalopathy or pericarditis)
Pateints with risk of AKI whom require investigation using contrast agents are given what to minimise risk?
IV fluids
