AKI Flashcards
What is AKI
Acute kidney injury- defined as an acute drop in renal function characterised by a rise in serum creatinine levels
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
List some of the functions of the kidneys
- waste excretion
- acid base balance
- blood pressure ( renin)
- water hormone/ homeostasis
- Vit D
Risk factors for AKI
hronic kidney disease
Heart failure
Diabetes
Liver disease
Older age (above 65 years)
Cognitive impairment
Nephrotoxic medications such as NSAIDS and ACE inhibitors
Hypovolemia
Nephrotoxic drugs
Trauma
What medications are deemed nephrotoxic
Ibuprofen- NSAID
Naproxen
Aminiglycosides
ACE inhibitors
Aetiology of AKI
Split into pre renal, renal and post renal
What are the pre renal causes of AKI
- Dehydration
- Hypotension
- Heart Failure
- Low blood volume
- liver failure
- renal artery stenosis
- Drugs NSAIDs or ACEi
What causes pre renal issues
HYPOVOLAEMIA
Due to inadequate blood supply to kidneys reducing filtration of blood
What can cause renal AKI
Split into 4
Glomerular- glomerular nephritis
Tubular - acute tubular necrosis due to prolonged ischaemia
Interstitial - acute interstitial nephritis
Vascular - vasculatis
Renal causes may be ..?
Glomerulonephritis
Interstitial Nephritis
Acute tubular necrosis
Rhabdomyolysis
What causes post renal AKI
Obstruction of the outflow of urine from the kidney causing back pressure into the kidney and reduced kidney function
Post renal causes include …?
- Kidney stones
- Masses such as cancer in the abdomen
- Ureter or uretral structures
T2DM, HTN, low urine osmolality , high urine Na+ K+ would suggest
Intrinsic causes
Investigations for AKI
-
Bloods
- FBC: anaemia and very high ESR suggests myeloma or vasculitis as underlying cause
- U&E
- Blood gas: check for metabolic acidosis
- Creatine kinase
-
Urinalysis: dipstick and microscopy
- Urine osmolality and electrolytes checked
- Leucocytesandnitritessuggest infection
- Proteinandbloodsuggestacute nephritis(but can be positive in infection)
- Glucosesuggests diabetes
Renal biopsy - for intrarenal cause
Renal USS - for post renal causes
Why would an US be used
to look for obstruction
Management of AKI
- Fluid rehydration with IV fluids in pre-renal AKI
- Stop nephrotoxic medications such as NSAIDS and antihypertensives that reduce the filtration pressure (i.e. ACE inhibitors)
- Relieve obstruction in a post-renal AKI, for example insert a catheter for a patient in retention from an enlarged prostate
- treat underlying cause - hypotension, infection, stones
- if severe: Dialysis
Complications for AKI
- Hyperkalaemia
- Fluid overload,
- heart failure
- pulmonary oedema
- Metabolic acidosis
- Uraemia (high urea) can lead to encephalopathy or pericarditis
Key diagnostic factors for AKI
- Hypotension
- Risk Factors
- Kidney insults
- Reduced urine production
What would bloods show for aki
Anaemia , high esr
High creatinine kinase
What is RIFLE
Three levels of renal dysfunction
RISK
INJURY
FAILURE
LOSS
END STAGE- RENAL DISEASE
3 stages of acute tubular necrosis
-Initiation: acute decrease in renal perfusion causing a reduced GFR
-Maintenance: GFR remains low for days or weeks
-Recovery: GFR recovers, regeneration of tubulointerstitial cells, polyuric phase may occur
ongoing ischaemia causes …..?
- pro inflammatory response with the release of cytokines , oxygen, free radicals and activation of leukocytes
- at this point if renal perfusion is not restored the ongoing ischaemia
why are tubular cells susceptible to ischaemia
they have a limited blood supply and a high metabolic demand
Pre - renal clinical manifestations of AKI
- Due to hypovolaemia
- reduced capillary refill time
- dry mucus membrane
- thirst
Intrinsic renal clinical manifestations of AKI
Vascular- arterial hypertension
Nephrotic syndrome- heavy proteinuria
Presentation of AKI
Substance accumulation
Hyperkalaemia - arrhythmias, muscle weakness
Hyperuraemia - NV,weakness, pericarditis
Fluid overload - oedema, hypovolemic shock, decreased urine
Acid build up - metabolic acidosis
What do we use to treat hyperkaleamia?
Calcium gluconate
presentation of AKI
Hyperkalemia
Hyperuraemia
Fluid overload
acid build up