Acute Kidney Injury Flashcards
Define Acute Kidney Injury (AKI)
- Increase in serum creatinine by ≥ 0.3 mg/dl (26.5 μmol/l) within 48 hours
- Increase in serum creatinine to ≥ 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days; or
- Urine volume <0.5 ml/kg/h for 6 hours
What are the main consequences of AKI?
Retention of waste products such as urea and creatinine
Dysregulation of fluid and electrolytes
Decreased urine output
Decreased eGFR
How many classifications of AKI are there?
3
Stage 1 is least severe
Stage 3 is most severe
Describe the key risk factors for kidney injury
Sepsis Myeloma Vasomotor drugs -ACEi, NSAIDs Toxins -Drugs (aminoglycosides, amphotericin, NSAIDs) -Radiocontrast -Haem pigments -Snake venom -Heavy metals (Pb, Hg) -Mushrooms
How are causes of AKI classified?
Pre-renal
Renal (intrinsic)
Post-renal - usually due to obstruction
What is the most common pre-renal cause of AKI?
Hypotension associated with sepsis and/or fluid loss (e.g. from vomiting/diarrhoea)
Give five examples of pre-renal causes of AKI
Volume depletion Oedema Hypotension Cardiovascular causes Renal hypoperfusion
Give six examples of renal (intrinsic) causes of AKI
Tubular injury Glomerular disease Acute interstitial nephritis Vascular disease Myeloma Eclampsia
Describe post-renal causes of AKI
Intraluminal – calculus, clot, sloughed papilla
Intramural – malignancy, ureteric stricture, radiation fibrosis, prostatic hypertrophy
Extramural – retroperitoneal fibrosis, pelvic malignancy
Describe the pathophysiology of AKI
Initiation: Kidney is exposed to toxic/ischaemic insult, and renal parenchymal injury begins to develop. At this stage, AKI is potentially preventable.
Maintenance: There is established parenchymal injury, with little/no urine being produced. Typical duration 1-2 weeks (up to several months).
Recovery: Gradual increase in urine output, and fall in serum creatinine (may take longer than diuresis).
Describe the cardinal signs of AKI
Decreased urine volume
High serum creatine
List the clinical signs of AKI
Decreased urine volume
High serum creatine
Nausea/vomiting
Symptoms of dehydration
Hypertension
Swollen, painless bladder (typical of chronic urinary retention)
Dehydration with postural hypotension and no oedema (e.g. if caused by vomiting)
Fluid overload – raised JVP, pulmonary oedema, peripheral oedema
Pallor, rash, bruising
Pericardial rub
What is the main reason for doing ultrasound and x-ray in patients with suspected AKI?
To rule out obstruction
Give five complications of AKI
Acidosis Electrolyte imbalance, particularly hyperkalaemia Intoxication (toxins) Overload Uraemic complications
Describe the supportive management of AKI
• Fluid balance – Volume resuscitation if volume deplete – Fluid restriction if volume overload • Optimise blood pressure – Give fluid /vasopressors – Stop ACE inhibitors / anti-hypertensives • Stop nephrotoxic drugs – NSAIDs – Aminoglycosides • Treat sepsis • Diagnose GN/other interstitial disease and give specific therapy • Catheter if indicated
