Acute Kidney Injury Flashcards
Definition of acute kidney injury?
Sudden acute drop in kidney function
How is acute kidney injury diagnosed?
Measuring serum creatinine
What is AKI characterized by?
-Rapid increase in blood urea & creatinine concentration caused by decreased glomerular filtration rate
Criteria for AKI?
- Rise in creatinine of >26.4micromol/L in 48 hours
- Rise in creatinine of >50%
- Urine output of <0.5ml/kg/hour for more than 6 hours
Who can commonly get AKI?
Common for patients already in hospital
Risk factors for AKI?
- CKD
- Heart fialure
- Diabetes
- Liver diseasse
- Older age (>65)
- Cognitive impairment
- Nephrotoxic medications: lithium, haldol
Classifying causes of acute renal injury?
Pre-renal
Renal/Intrarenal
Post-renal
Which is the most common type of cause of AKI?
Pre-renal
What is pre-renal caused AKI due to?
Inadequate supply to kidneys reducing filtration of blood
What can cause the inadequate blood supply resulting in pre-renal AKI?
- Dehydration
- Hypotension (shock/volume depletion)
- Heart failure (reduced effective circulating volume)
- Renal artery stenosis
- Renal hyperfusion
- Pharmacological (NSAIDs, ACEi)
What is renal AKI?
Where intrinsic disease in kidney is leading to reduced filtration of blood
Possible causes of Renal AKI?
- Ischaemic injury
- Nephrotoxic injury
- Immune-mediated injury
- Vasculitis/vascular disease
- Interstitial nephritis
- Glomerulonephritis
- Acute tubular necrosis
What is the cause of post-renal AKI?
Obstruction to outflow of urine from kidney, causing back-pressure into kidney and reduced kidney function
What is the cause of post-renal AKI called?
Obstructive uropathy
What can renal obstruction be caused by?
- Kidney stones
- Blood clots
- AAA
- Masses eg cancer (usually retroperitoneal)
- Ureter or ureteral strictures
- Enlarged prostate/prostate cancer
- Bladder issues (malignancy, blood clot)
- strictures
Signs/symptoms of AKI?
Non-specific:
- Anorexia, wt loss, fatigue, lethargy
- N/V
- Itch
- Fluid overload
Signs:
- Uraemia including itch
- Pericarditis
- Oliguria
What may pre-renal AKI presnet with?
- Hypovolaemia
- Hypotension
What does hypotension/hypovolaemia present as?
- Thirst
- Dizziness
- Weakness
- Diarrhoea
Investigations for AKI?
- Urinalysis: protein, blood, glucose, nitrates
- U&Es
- FBC and coags
- Immunology: ANA, ANCAM, GBM
- Protein electrophoresis
How many stages in KDIGO staging and what is it?
3 stages
Kidney disease Improving Global Outcomes criteria
Stage 1 KDIGO?
Serum Creatinine: -Increase >26 micromol/L within 48 hours OR -1.5 fold increase in serum creatinine OR - -GFR decrease
or
Urine output criteria:
- <0.5ml’Kg/h for 6 hours
Stage 2 KDIGO?
Serum creatinine criteria:
- 2 fold increase in serum creatinine
- GFR decrease >50%
OR
Urine output criteria:
-<0.5L/Kg/h for >12 hours
Stage 3 KDIGO?
Serum creatinine criteria: - 3 fold increase in serum creatinine OR -Increase >354 micromol/L OR -GFR decrease >75% OR started on renal replacement therapy
OR
Urine output criteria:
- <0.3mL/Kg/hr for >24 hours of 12 hours for anuria
Prevention of CKD?
- Avoiding nephrotoxic meds where possible
- Ensuring adequate fluid input in unwell patients
First step to treat AKI?
Treat underlying cause
How to treat underlying cause in pre-renal AKI?
Fluid rehydration
fluid challenge for hypovolaemia
- crystalloid (0.9% NaCl)// colloid - don’t use dextrose/Harmans (K)
- bolus of fluid - reassess - repeat
- if 1000 ml & no improvement - seek help
How to treat underlying cause for drug induced AKI?
Stop nephrotoxic meds (NSAIDs and antihypertensives) that reduce filtration pressure (ACEis)
How to treat underlying cause in Post-renal AKI?
Relieve obstruction eg insert catheter for enlarged prostate, nephroplasty
refer to urology if ureteric stenting required
How to manage fluids?
Hypovolaemia: fluid boluses (250-500ml crystalloid)
Hypervolemia: Diuretics?
What does hyperkalaemia predispose to?
Cardiac arrhythmias
What are patients with AKI susceptible to ?
Hyperkalaemia
Treating hyperklamiea?
IV calcium gluconate
What is the renal replacement therapy of choice?
Haemodialysis
Indications for haemodialysis?
A: Acidaemia E: Electrolytes (Hyperk) I: Ingestion/toxins O: Overload (fluid) U: Uraemia and uraemic complications
Complications of AKI?
- Hyperkalaemia
- Fluid overload, heart failure , pulmonary oedema
- Metabolic acidosis
- Uraemia can–> encephalopathy or pericarditis
What tests can diagnose cause of AKI?
- Urinalysis
- FBC
- Renal tract imaging
- Renal biopsy
How can AKI be prevented?
Miantaining adequate BP
Volume status
Avoiding nephrotoxic meds
Nephrotoxic drugs are?
- NSAIDs
- ACEis
- ARBs
a definition of pre-renal AKI?
reversible volume depletion leading to - oliguria <0.5 ml/kg/hr and increase in creatinine
what is the pathophysiology of pre-renal AKI?
hypovolaemia - haemorrhage - D&V - burns hypotension - cardiogenic shock - sepsis - anaphylaxis renal hypoperfusion (<20% CO) - NSAID/ COX2 - hepatorenal syndrome - ACEi/ARBs decreased renal perfusion activates RAAS to try and increase GFR if ACEi: can't activate RAAS - vasodilation of efferent arteriole
what is the prognosis of pre-renal AKI?
if untreated - acute tubular necrosis
- commonest hospital AKI
- sepsis, severe dehydration
- rabdomyolysis and drug toxicity
what are the possible pathogenesis of renal AKI?
vascular - vasculitis: GPA, MPA, renovascular disease
glomerulus - glomerulonephritis
interstitial nephritis - drugs: NSAIDs, penicillin, infection: TB, systemic: sarcoid
tubular injury - ischaemia - renal hypoperfusion, drugs: gentamicin, contrast and rhabdomyolysis
what is the presentation of renal AKI?
constitutional: anorexia, fatigue, lethargy
N&V
uraemia - itch
fluid overload - oedema, SOB, HTN, effusion
oliguria
how is renal AKI managed?
investigations U&E – marker of renal function: Na, Ur, Cr FBC &Coagulation o abnormal clotting – sepsis o anaemia – EPO urinalysis – haematoproteinuria USS – obstruction immunology – ANA (SLE), ANCA, GBM Protein electrophoresis & BJP – myeloma Treatment establish good perfusion pressure: fluid resuscitation - inotropes, vasopressors treat underlying cause: antibiotics if sepsis stop nephrotoxics dialysis if anuric & uraemia
hyperkalaemia
normal K 3.5- 5.0
hyperkalaemia >5.0
life-threatening >6.5
how is hyperkalaemia investigated?
muscle weakness
ECG
- peaked T waves (6-7mmol)
- flattened p wave, prolonged PR, depressed ST, peaked T wave (7-8 mmol)
- atrial stand still, prolonged QRS, peaked T wave (8-9 mmol)
- sine-wave (>9 mmol)
how is hyperkalaemia managed?
cardiac monitor & IV access
protect myocardium: 10ml 10% calcium gluconate (2-3 min)
move K+ back into cells
- insulin-actrapid 10 units with
- 50ml 50% dextrose (30 min)
- salbutamol nebs (90 min)
prevent GI absorption - calcium resonium (NOT in acute setting)
indications for haemodialysis
hyperkalaemia (>7/>6.5 unresponsive to medical therapy
severe acidosis pH <7.15
fluid overload
urea > 40 (pericardial rub/effusion)
drugs to avoid in AKI
NSAID ACEi/ARB diuretics gentamicin contrast trimethoprim – hyperkalaemia K+ sparing diuretics
