Acute Kidney Injury (AKI) Flashcards
Define Acute Kidney Injury (AKI).
An abrupt (over hours to days) sustained rise in serum urea and creatinine due to a rapid decline in GFR, leading to a failure to maintain fluid, electrolyte and acid-base homeostasis.
It is usually but not always reversible or self-limiting.
Simple terms: Acute drop in kidney function.
What is the affect of AKI on creatinine and urine output?
- Creatinine is raised.
- Urine output is reduced.
What is a normal GFR?
60ml/min/1.73m2 +
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 2 systems used for AKI classification?
- RIFLE
- KDIGO
Describe the RIFLE classification system for AKI.
Criteria:
* Risk
* Injury
* Failure
* Loss
* End-stage renal disease
What are the stages of the KDIGO system used for AKI?
1 - 150-200% increase in creatinine. less than 0.5ml/kg/hr for 6 hrs
2 - 200-300% increase in creatinine, less than 0.5mg/kg/hr for 12 hours
3 - less than 0.3ml/kg/hr
Give 5 risk factors for AKI.
- Increasing age (>65 YO)
- CKD.
- HF.
- Diabetes mellitus.
- Nephrotoxic drugs e.g. NSAIDs and ACEi.
- Contrast dyes
- Infection
- Dehydration
- Peripheral vascular disease
- Liver disease
- Past history of AKI
- Hypovolaemia
Give 3 pre-renal cause of AKI.
- Hypotension (shock)
- Heart failure
- Nephrotoxic drugs - NSAIDs, ACEi
- Bleeding
- Dehydration or haemorrhage
- Sepsis
Give 5 renal causes of AKI.
- Nephrotoxic drugs - NSAIDs, ACEi
- Vasculitis.
- Autoimmune.
- Acute tubular necrosis.
- Glomerulonephritis - nephritic / nephrotic syndromes
- Interstitial nephritis.
Give 3 post renal causes of AKI.
- Kidney stones
- Masses such as cancer in the abdomen or pelvis
- Ureter or uretral strictures
- Enlarged prostate or prostate cancer
- Benign prostate hyperplasia
- Urinary tract obstruction at ureter, bladder or prostate
Clinical presentation of AKI.
Often asymptomatic.
Pre-renal – hypotension (D&V, syncope, pre-syncope), signs of liver or heart failure (oedema)
Renal – infection, signs of underlying disease (vasculitis, glomerulonephritis, DM)
Post-renal – LUTS (BPH)
Universal:
- Oliguria (<0.5 mL/kg/hr >6hrs)
- High creatinine
- Hyperkalaemia – arrhythmias, muscle weakness
- Uraemia – N&V, weakness, pericarditis (if severe), platelet dysfunction (bleeding)
- Hypocalaemia / hyperphosphataemia (vitamin D def)
- ?Trauma – signs of direct injury
What investigations might you do to determine whether someone has AKI?
Establish the cause.
- Urinalysis
- Urine dipstick testing for blood, protein, leucocytes, nitrites and glucose - Ultrasound
- CT-KUB (kidney, ureter, bladder)
- Bloods
- U&E (eGFR)
- Creatinine
Management of AKI.
- Treat underlying cause
Pre-renal:
- Volume depletion with fluids
- Treat sepsis with antibiotics
Renal:
- Referral to nephrology
Post-renal:
- Relieve obstruction e.g. catheterise
- Consider a CT KUB - Stop nephrotoxic drugs
- NSAIDs, ACEi, Gentamycin, amphotericin - Optimise fluid balance
- Diet: Na+/K+ retriction and supply vitamin D
- Renal replacement therapy (RRT)
What drugs should be stopped in AKI?
NSAIDs, ACEi
What antibiotics commonly cause AKI?
Macrolide e.g. gentamycin – causes tubular necrosis
Give 3 complications of AKI.
- Hyperkalaemia - causes arrythmia
- Fluid overload - causes pulmonary hypertension
- Metabolic acidosis
- Uraemia - causes encephalopathy or pericarditis
How can hyperkalaemia be treated in AKI?
- Give calcium gluconate to protect the myocardium.
- Give insulin and dextrose (glucose).
Insulin drives K+ into cells and dextrose is to rebalance the blood sugar.
How would you treat acidosis in AKI?
Sodium bicarbonate
How would you treat pulmonary oedema?
Using diuretics e.g. Furosemide or dialysis/haemofiltration
