Renal 2) AKI Flashcards
What is an acute kidney injury?
Rapid fall in glomerular filtration rate which impedes kidney’s normal functions within hours to days
What is an AKI stage 1?
Increase in serum creatinine of ≥26 micromols/L within 48h or 1.5-2 fold increase from baseline
Urine output <0.5ml/kg/h for >6h
What is an AKI stage 2?
Increase in serum creatinine to >2-3 fold from baseline
Urine output <0.5ml/kg/h for >12h
What is an AKI stage 3?
Increase in serum creatinine to >3 fold from baseline or serum creatinine >354micromol/l with an acute increase of ≥44micrmol/L
Urine output <0.3ml/kg/h for 24h or anuria for 12h
What is creatinine?
Normal product of muscle turnover
Transported by blood and excreted by kidneys
Why is creatinine not reliable?
Muscle increases creatinine
Decreased creatinine levels in pregnancy due to increased fluid
What is the normal creatinine range in Brighton?
60-100 micromols/L
Individual to each patient
What is oliguria?
<0.5mlg/kg/h urine output
Usually <500ml/24h in adults
What is anuria?
No urine output
<100ml /24h
What are the 4 phases of an AKI?
Onset phase
Oliguric / anuric phase
Polyuric / diuretic phase
Recovery phase
What is the onset phase?
Renal blood flow 25% of normal
Tissue oxygenation 25% of normal
Urine output <0.5ml/kg/h
What are some common triggering events for an AKI?
Significant blood loss
Fluid loss
Diabetes insipidus
What is the oliguric / anuric phase?
Urine output <400ml/day
Increases in blood urea nitrogen and creatinine levels
Electrolyte disturbances, acidosis and fluid overload
What is the polyuric / diuretic phase?
Occurs when cause of AKI is corrected Renal tubule scarring and oedema Increased glomerular filtration rate Daily urine output >400ml Possible electrolyte depletion from excretion of more water and osmotic effects of high blood urea nitrogen
What is the recovery phase?
Decreased oedema
Normalisation of fluid and electrolyte balance
Return of GFR to 70-80% of normal
What are the functions of the kidneys?
Excretion of toxins e.g. urea Electrolyte balance Acid-base balance Fluid balance BP control Control of bone metabolism, vitamin D activation, phosphate excretion Production of erythropoietin
What are the symptoms of fluid overload?
Breathlessness
Orthopnoea
Limb swelling
What are the 4 main indications for dialysis in AKI?
Refractory hyperkalaemia
Pulmonary oedema
Refractory acid/base disturbance
Uraemic complications
What are some pre-renal causes of AKI?
Decrease in perfusion pressure resulting in ischaemia or infarction
Bleeding Septic shock Dehydration MI Iatrogenic Renal artery stenosis
What are some renal causes of AKI?
Direct toxic effects - drugs - calcium Overproduction leading to blockage of tubules - rhabdomyolysis - myeloma Inflammation in kidney - glomerulonephritis - interstitial nephritis - Acute tubular necrosis
What are some post-renal causes of AKI
Stones Ureteric / urethral strictures BPH Prostate cancer Urinary retention
What are some chronic background risks for AKI?
Elderly CKD Cardiac failure Liver disease Diabetes Vascular disease Background nephrotoxic medications
What are some acute risk factors for AKI?
Sepsis and hypoperfusion
Toxins
Obstruction
Parenchyma
What are some red flags in the history for AKI?
Haemoptysis Rashes Joint pain / swelling ENT Significant acute limb swelling Urine frothiness Jaundice
What drugs should be stopped in AKI?
ACE inhibitors Angiotensin receptor blockers NSAIDs Any diuretics Metformin
What are the causes of polyuria?
Known and common phase of AKI Post-relief obstruction Diabetes mellitus Psychogenic Beer potomania Endocrine causes e.g. diabetes insipidus
How should polyuria be managed?
Encourage patient to drink
Provide IV fluids to match output if dry
