AKI Flashcards
What is the definition of an AKI?
Rise in Cr 26+ micromol/L in 48h
OR
50% or more rise in Cr over 7d
OR
Fall in urine output to <0.5ml/kg/h for >6h in adults
OR
25% or more fall in eGFR in 7d
What are the three categories of causes and which is most common?
Pre-renal - most common
Renal
Post-renal - least common
What is the pathophysiology of pre-renal causes?
Decrease in kidney perfusion
What are the pre-renal causes?
Which is most common?
Vol depletion - diarrhoea, blood loss, dehydration (MOST COMMON)
Decreased CO - MI, HF
Sepsis
Drugs e.g. ACEi, NSAIDs
- reduce BP and renal blood flow
Renal A stenosis
Which two drugs should you SHOULDN’T give together?
ACEi and NSAIDs
What is the pathophysiology of renal causes?
Direct damage to kidney
What are the renal causes of AKI?
Vascular - vasculitis, malignant HTN
Tubular - acute tubular necrosis**, rhabdomyolysis, myeloma, radiocontrast (common), drugs e.g. abx
GN
Interstitial nephritis
How does myeloma cause AKI?
Light chains are toxic to tubules
What is the pathophysiology of post-renal causes and what are they?
Obstruction of urinary flow
Causes:
- Tumours
- Stones
- Strictures
- Blood clots
- BPH
Name 4 RF
Elderly >65y CKD Chronic conditions - DM, HF (toxic drugs), liver disease Neurological/cognitive impairement Cancer - myeloma/drugs Previous AKI Post-op - sepsis, hypovolaemia Meds - NSAIDs, contrasts
What are the SX?
Depends on the cause
Reduced urine output
Vomiting
- Early - cause
- Late - uraemia
Dizziness (pre-renal = orthostatic)
Orthopnoea - fluid overload
HTN
HypoTN
Uraemia - altered mental state, pericarditis, pruritus/bruising, fatigue/nausea
Pulmonary/ peripheral oedema
Arrhythmia - hyperK and acid-balance changes
What IX need to be undertaken?
U&E + Cr
- high Cr
- hyperK - metabolic acidosis
Urine dip, MCS
- UTI - leucocytes/nitrites
- GN - blood/protein
FBC
- anaemia (CKD/blood loss)
- leucocytosis
- thrombocytopenia (HUS, TTP)
ECG - hyperK
Renal USS - done within 24h if no identifiable cause
Name 5 nephrotoxic drugs
CANT DAMAG
Contrast Abx - penicillin, rifampicin NSAIDs Therapeutic Index (narrow) - ?lithium Diuretics ACEi Metformin ARB Gentamicin/Gold
What is creatinine?
What is it used to IX kidney function?
Waste product of normal muscle metabolism
It is a long-standing measure of kidney function because it is purely excreted by kidneys
What factors can creatinine be affected by?
Muscle mass - higher in those with higher muscle mass
Ethnicity
Gender - higher in males
Age - increase with age
Can a pt still have an AKI with a Cr in reference range?
What else can indicate AKI other than Cr?
Yes
Change in urine output may be the first to change
What is KDIGO?
AKI staging
Look at table in renal lec notes
What is the MX?
Stop nephrotoxic drugs
Supportive - careful fluid balance to maintain perfusion of kidneys but avoid fluid overload
RX CAUSE!!!
- Pre-renal: Fluid, stop drugs, RX underlying cause
- Renal: Biopsy/referral
- Post-renal: clear obstruction, catheterise, CT renal tract
HyperK:
- IV Ca gluconate to stabilise
- Combined insulin/dextrose infusion + neb salbutamol for cellular shift
- Calcium resonium, loop diuretics, dialysis to remove K from body
Renal Replacement Therapy
(Haemodialysis)
- used if pts not responding to medical RX of complications e.g. hyperK, severe acidosis (HCO3 <15) or uraemia
Refer
When do you refer to renal?
- Persistent oliguria
- Serum Cr >350 umol/L
- Indication for dialysis – hyperkalaemia, severe acidosis (HCO3 <15), pulmonary oedema
- Need for iodinated contrast
- Blood and protein in urine
- No clear cause for AKI
Which drugs need to be stopped?
NSAIDs Aminoglycosides - gentamicin ACEi ARBs Diuretics Metformin Lithium Digoxin
Which drugs are safe to continue in an AKI?
Paracetamol Warfarin Statins Aspirin (at 75mg OD) Clopidogrel BBs
What are the causes of intrinsic renal failure?
INTRINSIC
Ischaemia Nephrotoxic Abx (gentamicin, vancomycin) Tablets (ACEi, NSAIDs) Radiological contrast Injury (rhabdomyolysis) Negatively bifringent crystal (gout) Syndromes (GN) Inflammation (vasculitis) Cholesterol emboli
