AKI Flashcards
What are the main functions of the kidney?
Filtration of toxins and metabolic waste products Solute and water homeostasis EPO production Activation of vitamin D-> VD3 Renin sythesis-> RAAS
What is an AKI?
Acute drop/decrease in kidney function rise in creatinine and decreased urine out over a few days
NICE:
Rise in creatinine >25 micromol/L in 48 hrs
Rise in creatinine >50% in 7 days
Urine output of <0.5ml/kg for >6 hrs
What are the 3 stages of AKI and how are they defined?
Stage 1
-1.5-1.9 x increase in creatinine baseline
Stage 2
-2-2.9 x increase in creatinine baseline
Stage 3
-3 x increase in creatinine baseline
I.e. lowest number corresponds with stage
What are risk factors for AKI?
Current infection Surgery CKD Heart failure Liver disease >65 yo Cognitive impairment Nephrotoxic medications i.e. NSAIDs or ACEi Contrast medium used in CT scans
How might someone with an AKI present?
Reduced urine output
Evidence of dehydration
Nausea/Malaise/Confusion = due to the build up of nitrogenous waste products
Disrupted plasma pH= retention of hydrogen
What are the causes of an AKI?
ALWAYS SAY:
“PRE-RENAL, RENAL AND POST-RENAL”
What are the pre-renal causes of AKI?
States leading to impaired perfusion to the kidney leading to reduced filtration due to hypovolaemia or hypotension:
Haemorrhage Sepsis Dehydration Drugs i.e. loop diuretics/antihypertensives 3rd spacing of fluid i.e. ascites HF Overdiuresis Hepatorenal syndrome (see portal hypertension cards) Renovascular disease
What are the renal causes of AKI?
Anything which causes intrinsic damage to the kidney causing decreased filtration of blood
Nephrotoxic drugs (Gentamycin/chemotherapy/CT contrast)
Interstitial nephritis
Acute tubular necrosis
Glomerulonephritis
Rhambdomyelitis (due to increased deposition of creatinine kinase in the glomerulus)
Vascular disease (HUS/TTP/thrombosis/vascularitis)
Lymphoma
What are the post renal causes of AKI?
Anything causing a blockage/obstruction of flow of urine leading to back pressure into the kidney and reducing the renal function
Renal stones BPH Prostate cancer Urethral strictures Ascending UTI
What investigations would you do for someone suspected of AKI?
FBC+ CRP= looking for signs of infection
U+Es= urea:creatine ratio and eGFR
Blood cultures= if sepsis
LFT= hepatorenal syndrome
VBG= look for bicarbonate (i.e. might be reduced if it is an acute on chronic AKI)
Urinalysis for protein, blood, leucocytes, nitrites and glucose
- leukocytes + nitrites= infection
- protein + blood= acute nephritis
- glucose= suggests diabetes
USS
-if suspecting obstruction
ECG
-electrolyte disturbance causing rise in potassium-> can cause arrythmias
CXR
-if suspecting pneumonia i.e. can cause AKI as side effect
How would you manage someone with an AKI?
Pre-renal:
- IV rehydration to correct volume depletion
- cardiac support
- treat sepsis
- stop nephrotoxic drugs
Renal
-refer to renal team
Post-renal
- Catherterise to monitor urine output
- Relieve obstruction i.e. nephrostomy and urological intervention to bypass LUT
Need to assess fluid status
What are the signs that someone is hypovolaemic?
How should they be managed?
Low BP
Decrease urine output
Decrease skin turgor
500ml crystalloid over 15 mins
Repeat bolus
NOTE: need to stop giving bolus if not euvolaemic after 2 litres
What are the signs that someone is hypervolaemic?
How should they be managed?
Hypertensive
Lung base crackles
Peripheral oedema
Galloping rhythm
Fluid restriction
Diuretics
What medications are safe in an AKI and which need to be stopped?
Safe: paracetamol and warfarin
Stop:
- NSAIDs
- aminoglycosides
- ACEi
- Angiotensin II receptor antagonist
- diuretics
What serious complication can occur in an AKI?
What are the different steps to managing this?
Hyperkalaemia (treat when >6.5 or if ECG changes)
1st=Calcium gluconate
-stabilises the cardiac membrane to protect the heart from going into an arrhythmia but does not lower potassium levels
2nd= Salbutamol nebs and dextrose
3rd
- calcium resonilium
- dialysis
- loop diuretics i.e. non-potassium sparing
