AKI Flashcards
What is an Acute Kidney Injury?
Syndrome of decreased renal function, measured by serum creatinine or urine output, occurring over hours to days.
What are the three different findings that diagnose an acute kidney injury?
- Rise in creatinine >26umol/L within 48h
- Rise in creatinine >1.5x baseline within 7 days
- Urine output <0.5ml/kg/h for >6 consecutive hours
What determines the severity of an acute kidney injury?
Highest creatinine rise or longest period/severity of oliguria.
What serum creatinine changes are present at each stage of an acute kidney injury?
- Rise >26.5umol/L or 1.5-1.9x baseline
- 2-2.9x baseline
- > 353.6umnol or >3x baseline or RRT
What urine output is present at each stage of acute kidney injury?
- <0.5ml/kg/h for 6-12h
- <0.5ml/kg/h for >12h
- <0.3ml/kg/h for >24h or anuria for >12h
What are the commonest causes of acute kidney injury?
Acute tubular injury:
- Sepsis
- Major surgery
- Cardiogenic shock
- Hypovolaemia
What are the prerenal causes of acute kidney injury?
- Hypovolaemia - haemorrhage, D&V, burns, pancreatitis
- Reduced CO - cardiogenic shock, MI
- Systemic vasodilation - sepsis, drugs
- Renal vasoconstriction - NSAIDs, ACEi, ARBs, hepatorenal syndrome
What are the renal causes of acute kidney injury?
- Glomerular - glomerulonephritis
- Interstitial - drug reaction, infection, sarcoid infiltration
- Vessels - vasculitis, DIC
- Tubular - Acute Tubular Necrosis
What are the postrenal causes of acute kidney injury?
Obstruction:
- Within renal tract - stone, malignancy, stricture, clot
- Extrinsic compression - pelvic malignancy, BPH, retroperitoneal fibrosis
What are the risk factors for developing an AKI?
Pre-existing CKD, old age, male, CVD, malignancy, diabetes mellitus, chronic liver disease, tubulointerstitial nephritis.
What signs and symptoms may be present in AKI?
- Signs - hypotension/hypertension, tachycardia
2. Symptoms - N&V, dizziness, orthopnoea, anuria, oliguria uraemic symptoms
What are the metabolic disturbances in AKI?
- Hyperkalaemia
- Hyperphosphataemia
- Metabolic acidosis
- Elevated urea and nitrogen
What are the daily requirements of water, sodium, and potassium for an adult?
Water - 30ml/kg/d
Sodium - 1mmol/kg/d
Potassium - 1mmol/kg/d
What are the functions of the kidneys?
- Acid-base balance
- Water balance
- Electrolyte balance
- Toxin removal
- Blood pressure control
- EPO, vitamin D
How should you investigate a suspected AKI?
- FBC, U&Es, LFTs, VBG, lactate
- Urinalysis and culture
- USS KUB, CXR, ECG
- Catheterisation
- MRI/CT to further evaluate causes of obstruction from USS
- Management requires diagnosis and treatment of underlying aetiology
How do you treat a prerenal AKI?
Correct volume depletion/increase renal perfusion via cardiac support, treat sepsis.
How do you treat a renal AKI?
Refer for likely biopsy and specialist treatment.
How do you treat a post-renal AKI?
Catheter, nephrostomy, urological intervention.
Which drugs are neprhotoxic?
DIAMOND HL: D - diuretics I - IV contrast A - antibiotics M - metformin O - opiates N - NSAIDs D - digoxin H - heparin L - lithium
What are the indications for renal replacement therapy in AKI?
- Fluid overload/pulmonary oedema unresponsive to medical therapy.
- Uraemia (e.g. pericarditis, encephalopathy)
- Severe/prolonged acidosis (pH<7.2), may be managed with bicarbonate.
- Recurrent/persistent hyperkalaemia.
What are the signs and symptoms of hypovolaemia?
Hypotension, oliguria, non-visible JVP, poor tissue turgor, tachycardia, daily weight loss.
What are the signs and symptoms of hypervolaemia?
Early - hypertension, raised JVP, lung crepitations, peripheral oedema
Late - hypotension, skin turgor, increased CRT
How is hypovolaemia in an AKI treated?
- 500ml crystalloid over 15 mins (saline/Hartmann’s)
- Reassess fluid state
- Further boluses of 250-500ml with review after each
- Stop when euvolaemic or seek expert help when 2L given.
How is hypervolaemia in AKI treated?
- Fluid resuscitation, give drugs in minimal fluid.
- Diuretics only in symptomatic overload.
- RRT
