What is the definition of acute kidney injury?
An abrupt (<48hrs) reduction in kidney function defined as:
An absolute increase in serum creatinine by >26.4µmol/l
Increase in creatinine by >50%
A reduction in urine output
What markers are used to stage acute kidney injury?
What is stage 1 acute kidney injury?
Increase >26µmol/L or
Increase > 1.5-1.9 x reference Cr
< 0.5 mL/kg/hr for > 6 consecutive hrs
What is the definition of stage 2 acute kidney injury?
Increase > 2 to 2.9 x reference serum Cr
<0.5ml/hour for > 12 hours
What is the definition of stage 3 acute kidney injury?
Creatinine (one of):
Increase > 3 x reference serum Cr
Increase to > 354 µmol/L
Need for RRT
<0.3 mL/kg/hr for > 24hrs
12 hrs for anuria
How can causes of acute kidney injury be classified?
What are the main pre-renal causes of AKI?
What can cause hypovolaemia resulting in AKI?
Volume depletion (e.g. D&V, burns)
What can cause hypotension resulting in AKI?
Distributive shock (e.g. sepsis, anaphylaxis)
What can cause renal hypoperfusion causing AKI?
NSAIDs / COX-2
ACEi / ARBs
How do NSAIDs cause hypoperfusion of the kidneys?
Prostaglandin inhibition/vasodilatation inhibition of the efferent arteriole
Essentially compromises the blood supply to the kidney
Should patients taking ACEi continue their drugs during episodes of D&V?
No: renal perfusion is going to decrease during D&V due to significant fluid loss, and continuing ACEi may cause a major fall in GFR
What pathology can be seen in the kidneys if prerenal AKI is left untreated?
Acute tubular necrosis
What is the commonest form of AKI in the hospital?
Acute tubular necrosis
What are some of the causes of acute tubular necrosis AKI?
How can hydration be assessed?
Clinical observations (BP, HR, UO)
Capillary Refill Time
How is hypovolaemia treated?
Crystalloid (0.9% NaCl) or Colloid (Gelofusin)
Give bolus of fluid then reassess and repeat as necessary
If >1000mls IN and no improvement, seek help
What are the four types of causes of AKI?
What are the symptoms of AKI?
Anorexia, weight loss, fatigue, lethargy
Nausea & Vomiting
What are the signs of acute kidney injury?
Fluid overload including oedema, pulmonary oedema, effusions (pleural & pulmonary)
Uraemia incl itch, pericarditis
What initial blood tests would you do if AKI suspected?
U&Es (is potassium high)
FBC and coagulation screen
Urinalysis (proteinuria suggeting active GN)
USS (?Obstruction ?Size)
Immunology (ANA (SLE), ANCA (Vasculitis), GBM (Goodpastures))
Protein electrophoresis & BJP
(?myeloma (everyone over 50yrs))
What are the urgent indications for renal biopsy?
Suspected rapidly progressive GN
Positive immunology & AKI
What are the semi-urgent indications for renal biopsy?
Unexplained AKI to gain a diagnosis
Rule out obstruction, volume depletion & acute tubular necrosis
What are the life threatening complications of AKI?
Fluid Overload (Pulmonary oedema)
Severe Acidosis (pH < 7.15)
Uraemic pericardial effusion
Severe Uraemia (Ur >40)
What causes post-renal AKI?
What is a normal serum potassium level?
What serum potassium levels define hyperkalaemia and then life-threatening hyperkalaemia?
What are the ECG changes seen in hyperkalaemia?
Tented/large T waves
QRS complex widening
VF then ventricular standstill
What drug is given in hyperkalaemia to protect the myocardium?
Which drugs are given in hyperkalaemia to move potassium back into the cells?
Insulin (actrapid 10units) with 50mls 50% dextrose (30 mins)
Salbutamol nebuliser (90 mins)
How long are repeated doses of calcium gluconate and insulin dextrose given?
Calcium gluconate until ECG normal
Insulin dextrose until serum potassium normal
What are the urgent indications for haemodialysis?
Hyperkalaemia: >7 or >6.5 and unresponsive to therapy
Severe acidosis (<7.15)