Acute Kidney Injury

Question 1

COMMS: Normal kidney function

Answer 1

​Normal kidney function

• Filter waste products in blood and carry to urine to be passed out
• Help control BP - control amount of water passing in and out of blood and control hormones that alter BP
• Produce hormone - erythropoetin - that controls production of red blood cells from bone marrow
• Regulate levels of fluid in body
• Regulate levels of salt and other chemicals

Question 2

COMMS: AKI

Answer 2

• Sudden injury to kidney
• Can no longer perform normal functions
• Fluid salts and chemicals in blood can rise or fall as no longer regulated
• This imbalance can affect other organs

Question 3

RISK FACTORS: AKI

Answer 3

• Age >75 yrs
• Chronic kidney disease
• Cardiac failure
• Peripheral vascular disease
• Chornic liver disease
• Diabetes
• Sepsis
• Poor fluid intake
• Hx urinary symptoms
• Drugs
  
  • NSAIDs
  • ACEi/AR2B
  • Aminoglycosides - GENTAMICIN
  • Diuretics

Question 4

AETIOLOGY: AKI

Answer 4

Pre-renal (ischaemia of kidney as poor blood flow)

• Hypotension
• Renal artery stenosis (+/- ACEi)

Intrinsic Renal

• Tubular - Acute tubular necrosis (often due to nephrotoxins/contrast)
• Glomerular - SLE, HSP, drugs, infections
• Interstitial - lymphoma, infection, tumour lysis syndrome
• Vascular - vasculitis, malignant HTN, thrombus, HUS/TTP

Post-Renal (urinary tract obstruction)

• Stones/clots
• Malignancy

Question 5

What pathology happens when kidneys stop working?

Answer 5

• Oliguria (reduced urine output) = <0.5ml/kg/hr
• Fluid overload
• Rise in serum molecules which kidney normally excretes
  
  • CREATININE = high
  • POTASSIUM = high
  • UREA = high

Question 6

CLINICAL FEATURES: AKI

Answer 6

• Asymptomatic (initially)
• Urine ouput = Low
• Pulmonary and peripheral oedema
• Arrhythmias (2nd to K+/acid-base changes)
• Uraemia features
  
  • Fatigue
  • Weakness
  • Itching
  • Loss of appetite
  • CNS disturbances

Question 7

INITIAL ASSESSMENT: AKI

Answer 7

• Circulation (ABCDE)
  
  • Volume status - BP, JVP, skin turgor, Cap refill, urine output (catheter)
• K+ check on venous bood and ECG (hyperkalaemia)
• Hx
  
  • Co-morbidity check: renal disease, recent fluid intake/loss, new drugs
• Examination:
  
  • Palpable bladder, palpabale kidneys (polycystic disease), abdo masses, renal bruits
• Urine dip
  
  • Infection = leucocytes + nitrates
  • Glomerular disease = blood + protein
• Urine microscopy
  
  • Casts, crystals, cells
  • Infection culture

Question 8

INVESTIGATIONS: AKI

Answer 8

Bloods

• Serum creatinine = > 26 micromol/litre w/i 48 hours
• Serum creatinine = > 50% from baseline in last 7 days
• Urine output = <0.5ml/kg/hour for >6h
• Imaging*
• Renal US if obstruction suspected

Question 9

MANAGEMENT: AKI

Answer 9

Supportive

• Careful fluid balance
• Stop any exacerbating drugs
• Treat hyperkalaemia promptly
• Specialist referral if:
  
  • Unknown cause
  • Severe
  • Urinary obstruction
• Renal replacement therapy (haemodialysis) if severe

Question 10

Which drugs are usually stopped in AKI?

Answer 10

• NSAIDs
• Aminoglycosides e.g. gentamicin
• ACEi
• AR2Bs
• Diuretics

Question 11

What are the main indications for dialysis in AKI?

Answer 11

• Severe pulmonary oedema
• Persistent hyperkalaemia
• Severe metabolic acidosis
• Uraemic complications (e.g. encephalopathy/pericarditis)
• Drug overdose (BLAST)
  
  • Barbiturates
  • Lithium
  • Alcohol
  • Salicylates
  • Theophylline