Acute Kidney Injury Flashcards
What is the mortality for severe acute kidney injury?
Over 50% for most and up to 80% in the context of multi-organ failure needing dialysis
What can be looked at to help diagnose acute kidney injury?
Solute clearance = urea/creatine
Urine output = oliguria
Need for dialysis = increased urea or K+, fluid overload
What is acute kidney injury defined as?
Abrupt (<48hrs) reduction in kidney function = absolute increase in serum creatine by >26.4 micromol/l OR increase in creatine by >50% OR a reduction in urine output
What can be used to categorise acute kidney injury?
KDIGO staging
What are the patient risk factors for acute kidney injury?
Older age, CKD, diabetes, cardiac failure, liver disease, PVD, previous AKI
What are some exposure risk factors for acute kidney injury?
Hypotension, hypovolaemia, sepsis, deteriorating NEWS, recent contrast, exposure to certain medications
What are the causes of acute kidney injury split into?
Pre-renal (functional), renal (structural) and post-renal (obstruction)
What are the causes of pre-renal AKI?
Hypovolaemia = haemorrhage, volume depletion
Hypotension = cardiogenic shock, distributive shock
Renal hypoperfusion = NSAIDs, COX2, ACEi, ARB, hepatorenal syndrome
What is the underlying mechanism of pre-renal AKI?
Reversible volume depletion leading to oliguria and increase in creatine
What is the urine output of pre-renal AKI?
Oliguria = <0.5 ml/kg/hr
How much of the total body weight do the kidneys account for?
0.5% = receive 20% of cardiac output
What does pre-renal AKI lead to if left untreated?
Acute tubular necrosis = most common form of AKI in hospital
What causes acute tubular necrosis?
A combination of factors leading to decreased renal perfusion = sepsis, severe dehydration, rhabdomyolysis, drug toxicity
How can the hydration of a patient with pre-renal AKI be assessed?
BP, heart rate, urine output, JVP, capillary refill time, oedema, pulmonary oedema
How may a patient with pre-renal AKI undergo fluid challenging for hypovolaemia?
Crystalloid (0.9% NaCl) or colloid (Gelofusion), don’t use 5% dextrose, give bolus of fluid then reassess and repeat as necessary, if >1L IN and no improvement seek help
What is renal AKI?
Diseases causing damage or inflammation to cells = categorised by structure (blood vessels, glomerular, interstitial, tubular)
What are some causes of vascular renal AKI?
Vasculitis, renovascular disease
What causes glomerular renal AKI?
Glomerulonephritis
What are some causes of interstitial renal AKI?
Nephritis due to drugs, infection (TB) or systemic disease (sarcoid)
What are some causes of tubular renal AKI?
Ischaemia (prolonged renal hypoperfusion), gentamicin, contrast, rhabdomyolysis
What are some non-specific symptoms of renal AKI?
Anorexia, weight loss, fatigue/lethargy, nausea and vomiting, itch, oedema and SOB due to fluid overload
What are some signs of renal AKI?
Hypertension, oedema, pleural/pulmonary effusion, uraemia (itch, pericarditis), oliguria
What are some clues that AKI might have a renal cause?
Sore throat, rash, joint pain, diarrhoea, vomiting, haemoptysis, recent contrast, eosinophilia, vascular bruit
What are some investigations done for renal AKI?
U & Es = marker for renal function, is K+ high?
FBC and clotting screen = abnormal clotting, anaemia
Urinalysis = haematoproteinuria
Immunology = ANCA, ANA, GBM
USS, protein electrophoresis, BJP
How is renal AKI treated?
Establish good perfusion pressure = inotropes/vasopressors, fluid
Treat underlying cause and stop nephrotoxics
Dialysis if still uraemic/anuric
What are some complications of renal AKI?
Hyperkalaemia, pulmonary oedema, fluid overload, severe acidosis (pH <7.5), uraemic pericardial effusion, severe uraemia (>40)
What is the underlying mechanism of post-renal AKI?
Obstruction of urine flow leads to back pressure (hydronephrosis) and thus loss of concentrating ability
What are some causes of post-renal AKI?
Calculi, cancer, strictures, extrinsic pressure
How is post-renal AKI treated?
Relieve obstruction = catheter, nephrostomy
Refer to urology if ureteric stenting needed
What is hyperkalaemia associated with?
Cardiac arrhythmias = peaked T waves on ECG
What is the normal range for potassium?
3.5-5
What is hyperkalaemia defined as?
Quantities >5.5
Life threatening if >6.5
How is hyperkalaemia assessed?
ECG and muscle weakness
How can the heart be protected from hyperkalaemia?
Protect the myocardium by giving 100ml of 10% of calcium gluconate (2-3 mins)
How is hyperkalaemia treated?
Move K+ back into cells = insulin (actrapid 10 units) with 50ml of 50% dextrose (30 mins), nebulised salbutamol (90 mins)
How is absorption of potassium from the GI tract during hyperkalaemia prevented?
Give calcium resonium (not in an acute setting)
What are some urgent indications for haemodialysis?
Hyperkalaemia >7 or >6.5 if unresponsive to therapy
Severe acidosis = pH <7.15
Fluid overload
Urea >40 (pericardial rub/effusion)
What is the mortality of AKI?
AKI alone = 10-30%
AKI with one other organ dysfunction = 30-50%
AKI as part of multi-organ failure = 70-90%
What is the recovery rate of renal function after AKI?
10-15% have no recovery of renal function
5-10% recover but have progressive CKD
Can dialysis reverse disease course?
No = it clears toxins but doesn’t alter the course of disease
