AKI Flashcards
What criteria is used to diagnose AKI?
rise in creatinine >26 in 48hrs
rise in creatinine >50% in 7 days
decrease in UO <0.5ml/kg/hr for >6hrs
what are KDIGO criteria for stage 1 AKI?
increase in creatinine 1.5-1.9x baseline
or increase in cr by >26.5
or reduction in UO <0.5ml/kg/hr for >6hrs
what are KDIGO criteria for stage 2 AKI?
increase in cr to 2-2.9x baseline
or reduction in UO to <0.5ml/kg/hr for >12hrs
what are KDIGO criteria for stage 3 AKI?
increase in cr to >3x baseline
or increase in creatinine to ?353.6
or reduction in UO to <0.3ml/kg/hr for >24hrs
or intiation of kidney replacement therapy
or if <18yo decrease in eGFR to <35
when do you need to refer to a nephrologist?
renal transplant
ITU patient w unknown cause of AKI
vasculitis, glomerulonephritis
tubulointerstitial nephritis
myeloma
AKI w no known cause
inadequate response to rx
complications of AKI
stage 3 AKI
CKD stage 4 or 5
qualify for renal replacement hyperkalaemia/metabolic acidosis/complications of uraemia/fluid overload
what can increase the risk of AKI?
emergency surgery ie risk of sepsis or hypovolaemia
intraperitoneal surgery
CKD eGFR<60
diabetes
HF
>65yo
liver disease
use of nephrotoxic drugs
- NSAIDs
- aminoglycosides eg gentamicin
- ACEi/ARB
- diuretics
what are the pre-renal causes of AKI?
- shock- inadequate renal perfusion- dehydration, haemorrhage, heart failure, sepsis
kidneys act to concentrate urine + retain sodium- high urine osmolality >500, low urinary sodium <20
- renovascular compromise
- RAS
- toxins: NSAIDs, ACEi
- thrombosis
- hepatorenal syndrome
what are the renal causes of AKI?
ATN
TIN
GN
most common- ATN (acute tubular necrosis)
damage to tubular cells due to prolonged ischaemia/toxins
kidneys can no longer concentrate urine or retain sodium- low urine osmolality<350, high urine sodium >40
rare causes- acute glomerulonephritis, acute interstitial nephritis, nephritic syndrome
what are the causes of ATN?
ischaemia: shock, HTN, HUS, TTP
direct nephrotoxins: drugs, contrast, hb
acutely- drug hypersenstiivity
what are post-renal causes of AKI?
SNIPPIN
Stone
neoplasm
inflammation- stricture
prostatic hypertrophy
posterior urethral valves
infection- TB, schisto
neuro- post-op, neuropathy
urinary tract obstruction results in hydronephrosis on USS
what is the cause of isolated rise in urea?
decreased flow eg hypoperfusion/dehydration
decreased flow leads to increased urea reabsorption (dehydration)
increased urea with protein meal- upper GI bleed, supplements
decreased urea with hepatic impairment (urea is produced from ammonia by liver in ornithine cycle)
what results in rise in both urea and creatinine?
decreased filtration ie renal failure
what is creatinine clearance?
volume of blood that can be cleared of a substance in 1 minute
how can people present wtih renal failure?
uraemia eGFR<15
protein loss + Na retention
fluid overload
acidosis
hyperkalaemia
anaemia
vitamin D deficiency
what are the symptoms of uraemia?
pruritus
n+v, anorexia, wt loss
lethargy
confusion
restless legs
metallic taste
paraesthesia- neuropathy
bleeding
chest pain- serositis
hiccoughs
what are the signs of uraemia?
pale sallow skin
striae
pericardial/pleural rub
fits
coma
what are the symptoms of hypernatraemia/protein loss?
polyuria, polydipsia
oliguria, anuria
SOB
what are the signs of hypernatraemia/protein loss?
oedema
raised JVP
HTN/hypotension
what are the symptoms of acidosis?
SOB
confusion
what are the signs of acidosis?
kussmaul respiration
what are the symptoms of anaemia?
SOB
lethargy
faint
tinnitus
what are the signs of anaemia?
pallor
tachycardia
ESM at apex
what are the symptoms of vitamin D deficiency?
bone pain
fractures
what are the signs of vitamin D deficiency?
osteomalacia
- looser’s zones (pseudo fractures)
- cupped metaphyses
what are the symptoms of hyperkalaemia?
palpitations
chest pain
weakness
what are the signs of hyperkalaemia?
tall tented T waves
flattened p waves
prolonged PR interval
widened QRS
sine-wave pattern-> VF
what are the signs of fluid overload?
oedema
high or low BP
S3 gallop
raised JVP
what is involved in clinical assessment of AKI?
assess for:
1. acute or chronic
2. volume depletion
3. GU tract obstruction
4. rare cause
what suggests chronic features of AKI?
hx of comorbidity- DM. HTN
long duration of symptoms
previously abnormal blood results
what suggests volume depletion?
postural hypotension
JVP not raised
tachycardia
poor skin turgor
dry mucous membranes
what suggests GU tract obstruction?
suprapubic discomfort
palpable bladder
enlarged prostate
catheter
complete anuria- rare in ARF
what are rare causes of AKI?
associated with proteinuria +/- haematuria
vasculitis- rash, arthralgia, nosebleed
what investigations are needed in AKI?
bloods- FBC, UE, LFT, glucose, clotting, Ca, ESR
ABG: hypoxia (oedema), acidosis, hyperK
GN screen- if cause unclear
urine- dip, MCS, chemistry (UE, PCR, osmolality, BJP)
ECG- hyperkalaemia
CXR- pulmonary oedema
renal US- renal size, hydronephrosis
what would suggest a pre-renal cause of AKI?
high osmolality
low urinary Na
because urine is concentrated and Na is reabsorbed
what are indications for acute dialysis?
persistent hyperkalaemia?7
refractory pulmonary oedema
symptomatic uraemia- encephalopathy, pericarditis
severe metabolic acidosis ph<7.2
poisoning eg aspirin
what are exogenous causes of nephrotoxicity?
NSAIDs
ACEi
immunsuppressants- ciclosporin, tacrolimus
contrast media
anaesthetics- enflurane
antimicrobials
- aminoglycosides
- vanc
- aciclovir
- sulphonamides
- tetracycline
- amphotericin
