Acute Kidney Injury Flashcards
What is acute kidney injury?
Rapid loss of glomerular filtration/renal function over hours-days following injury to the kidney, involving retention of urea and creatinine
What is the NICE criteria for AKI?
Rise in creatinine of ≥ 25 micromol/L in 48 hours
Rise in creatinine of ≥ 50% in 7 days
Urine output of < 0.5ml/kg/hour for > 6 hours
What are the 3 classifications of acute kidney injury causes?
Pre-Renal
- Inadequate blood supply to the kidney, reducing blood filtration
Renal/Intrinsic
- Damage to renal parenchyma causing reduced filtration of blood
Post-Renal
- Obstruction to urine outflow from the kidney causing back-pressure into the kidney
What are the pre-renal causes of AKI?
HF
Haemorrhage
Sepsis
Hypotension/shock
Vomiting and diarrhoea
Dehydration
Renal artery stenosis
What are the renal causes of AKI?
Glomerulonephritis
Vasculitis
Radiocontrast
Myeloma
Rhabdomyolysis
Toxins
What toxins can cause AKI?
(stop the damn drugs)
NSAIDS
Gentamicin/Aminoglyosides
ACEI and ARBS
Diuretics
Metformin
(Lithium and Digoxin increase risk of toxicity but does not cause AKI itself)
What are the post-renal causes of AKI?
Tumours
Prostate disease
Kidney stones
Ureter strictures
Give risk factors for AKI
Consider AKI in patient’s suffering from an acute illness or post surgery
Age >65
Previous AKI
HF
Liver disease
CKD
DM
Vascular disease
Cognitive impairment
Nephrotoxic medications
Contrast medians for CT
How does AKI present?
Oliguria
Oedema, pulmonary and peripheral
Arrythmias/palpitations, secondary to hyperkalaemia
Features of uraemia, such as pericarditis and encephalopathy
What investigations are used in AKI diagnosis?
Urinalysis
- Leucocytes and nitrites
- Protein and blood
- Glucose
U&E
- Increased creatinine and urea
ABG
- Metabolic acidosis
- Increased bicarbonate
US within 24 hours if no identifiable cause
- Exclude obstruction
Renal biopsy
ECG
- Hyperkalaemia changes
Myeloma screen
How is AKI managed?
Treat cause
Sepsis protocol
- Blood culture
- Hourly urine output of urea and creatinine
- IV fluids
- IV antibiotics
Medication review and stop nephrotoxic drugs
Fluid balance
- Volume resuscitation/fluid restriction
- IV fluids if necessary
- Catheter to monitor fluid outgoing
Hyperkalaemia management
Optimise BP
Renal replacement therapy/haemodialysis
- Indicated when patient is not responding to medical treatment of complications
How is hyperkalaemia managed?
IV calcium gluconate to stabilise myocardium
Shift K+ intracellularly via nebulised salbutamol and insulin-Dextrose infusion
Removal via diuretics, dialysis or anion exchange renins such as calcium resonium orally or enema
Give indications for dialysis
Pulmonary oedema
K+ >6.5mmol/l
pH<7.2
Pericarditis
Encephalopathy
Give indications for referral to a nephrologist?
Renal transplant
ITU patient with unknown cause of AKI
Vasculitis/ glomerulonephritis/ tubulointerstitial nephritis/ myeloma
AKI with no known cause
Inadequate response to treatment
Complications of AKI
Stage 3 AKI
CKD stage 4 or 5
Qualify for renal replacement hyperkalaemia / metabolic acidosis/ complications of uraemia/ fluid overload (pulmonary oedema)
Describe AKI stage 1
1.5-1.9x baseline serum creatinine or
>26.5 umol/l increase in creatinine or
<0.5ml/kg/h urine for 6-12 hours
Describe AKI stage 2
2.0-2.9x baseline serum creatinine or
<0.5ml/kg/h urine for >12 hours
Describe AKI stage 3
3.0x baseline serum creatinine or
>354 umol/l creatinine or
Initiation of replacement therapy or
<3.0ml/kg/h for >24 hours or
Anuria for >12 hours
Give complications of AKI
Metabolic acidosis
Electrolyte imbalance
- Hyperkalaemia
Fluid overload
- HF
- Pulmonary oedema
Uraemic complications
- Encephalopathy
- Pericardial rub with pericarditis
What is the most common cause of AKI?
Acute tubular necrosis (ATN) is the most common cause of acute kidney injury (AKI) seen in clinical practice
What causes ATN?
Ischaemia
- Shock
- Sepsis
Nephrotoxins
- Aminoglycosides
- Myoglobin secondary to rhabdomyolysis
- Radiocontrast agents
- Lead
How does ATN present?
Features of AKI
Muddy brown casts in urine
Describe the test results in pre-renal causes of AKI
Decreased urine Na (<20)
Increased urine osmolaity (>500)
Good response to fluid challenge
Raised serum urea:creatinine ratio
Normal urine
Describe the test results in intra-renal causes of AKI/acute tubular necrosis
Increased urine Na (>40)
Decreased urine osmolaity (<350)
Poor response to fluid challenge
Normal serum urea:creatinine ratio
Brown granular casts in urine
Proteinuria
Describe the U&E results in dehydration specifically
Urea is porportionally higher than the rise in creatinine
