Acute kidney injury Flashcards
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?
Createnine
Urine output
What is stage 1 acute kidney injury?
Createnine:
Increase >26µmol/L or
Increase > 1.5-1.9 x reference Cr
Urine output:
< 0.5 mL/kg/hr for > 6 consecutive hrs
What is the definition of stage 2 acute kidney injury?
Creatinine:
Increase > 2 to 2.9 x reference serum Cr
Urine output:
<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
Urine output:
<0.3 mL/kg/hr for > 24hrs
12 hrs for anuria
How can causes of acute kidney injury be classified?
Prerenal
Renal
Postrenal
What are the main pre-renal causes of AKI?
Hypovolaemia
Hypoperfusion
Hypotension
What can cause hypovolaemia resulting in AKI?
Haemorrhage
Volume depletion (e.g. D&V, burns)
What can cause hypotension resulting in AKI?
Cardiogenic shock
Distributive shock (e.g. sepsis, anaphylaxis)
What can cause renal hypoperfusion causing AKI?
NSAIDs / COX-2
ACEi / ARBs
Hepatorenal syndrome
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?
Sepsis
Severe dehydration
Rhabdomyolysis
Drug toxicity
How can hydration be assessed?
Clinical observations (BP, HR, UO)
JVP
Capillary Refill Time
Oedema
Pulmonary oedema
How is hypovolaemia treated?
Fluid challenge
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?
Vascular
Glomerular
Interstitial nephritis
Tubular injury
What are the symptoms of AKI?
Constitutional symptoms:
Anorexia, weight loss, fatigue, lethargy
Nausea & Vomiting
Itch
Fluid overload
Oedema, SOB
What are the signs of acute kidney injury?
Fluid overload including oedema, pulmonary oedema, effusions (pleural & pulmonary)
Uraemia incl itch, pericarditis
Oliguria
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?
Hyperkalaemia
Fluid Overload (Pulmonary oedema)
Severe Acidosis (pH < 7.15)
Uraemic pericardial effusion
Severe Uraemia (Ur >40)
What causes post-renal AKI?
Obstruction
What is a normal serum potassium level?
3.5-5.0
What serum potassium levels define hyperkalaemia and then life-threatening hyperkalaemia?
>5.5
>6.5
What are the ECG changes seen in hyperkalaemia?
Tented/large T waves
P-wave flattening
QRS complex widening
VF then ventricular standstill
What drug is given in hyperkalaemia to protect the myocardium?
Calcium gluconate
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)
Fluid overload
Urea >40
Pericardial rub/effusion
