Acute Kidney Injury Flashcards
describe mortality in AKI
predicted by its duration
increased risk with increase in creatinine
severe AKI can have mortality up to 50-80% in context of multi-organ failure requiring renal replacement therapy
cost implications of AKI?
extra 4.7 days in hospital
higher costs than breast, lung and skin cancer combined
definition of AKI?
an abrupt (<48 hrs) reduction in kidney function defined as
- absolute increase in serum creatinine by >26.4
- or increase in creatinine by >50%
- reduction in urine output
stage 1 AKI?
increase in creatinine > 26
or
increase > 1.5-1.9 X reference creatinine
urine output <0.5 ml/kg/hr for >6 consecutive hours
stage 2 AKI?
increase >2-2.9 X reference serum creatinine
urine output <0.5ml/kg/hr for >12 hrs
stage 3 AKI?
increase >3 X reference serum creatinine or increase to >354 or need for renal replacement therapy urine output <0.3ml/kg/hr for >24 hrs or 12 hrs for anuria
risk factors for AKI?
old age CKD diabetes cardiac failure liver disease PVD previous AKI gentamicin hypotension/hypovolaemia sepsis deteriorating NEWS recent radiological contrast drugs
3 groups of AKI?
pre-renal (functional) renal (structural) post renal (obstruction)
3 causes of pre-renal AKI?
hypovolaemia (haemorrhage, volume depletion - D&V, burns etc)
hypotension (cardiogenic shock, distributive shock - sepsis, anaphylaxis etc)
renal hypoperfusion (NSAIDs, COX-2, ACE/ARBs, hepatorenal syndrome)
how does pre renal AKI affect urine output?
reversible volume depletion leading to oliguria and increase in creatinine
- oliguria = <0.5ml/kg/hr
risk of antihypertensives in AKI?
reduce blood pressure and therefore reduce renal perfusion
if combined with e.g vomiting and diarrhoea which reduced blood volume further, can cause major drop in renal perfusion leading to major fall in GFR
perfusion requirements of kidneys?
receive 20-25% of whole cardiac output
untreated pre-renal AKI can lead to what?
acute tubular necrosis
what is acute tubular necrosis?
commonest form of AKI in hospital
due to combination of factors leading to decreased renal perfusion
what can cause acute tubular necrosis?
sepsis
severe dehydration
rhabdomyolysis
drug toxicity
how is pre-renal AKI assessed for hydration?
clinical observation
JVP, cap refill, oedema
pulmonary oedema
how is fluid given in pre-renal AKI?
crystalloid (0.9% NaCl) or colloid (gelofusin)
DO NOT USE DEXTROSE
give bolus of fluid then reassess and repeat as necessary
if >1 L has been given with no improvement, seek help
categories of renal AKI?
divided by structure affected: blood vessels glomerular disease interstitial injury tubular injury
vascular causes of renal AKI?
vasculitis
renovascular disease
glomerular causes of AKI?
glomerulonephritis
interstitial causes of AKI (interstitial nephritis)?
drugs
- NSAIDs, PPIs, penicillin, gentamicin
infection (TB)
systemic (sarcoidosis)
what can cause tubular injury AKI?
ischaemia
drugs (gentamicin)
contrast
rhabdomylolysis
symptoms and signs of AKI?
constitutional (weight loss, fatigue, lethargy)
nausea and vomiting
itch
fluid overload (oedema, breathless, pulmonary oedema, hypertension, effusions)
uraemia (including itch, pericarditis etc)
oliguria
examples of history which can point to cause of AKI?
sore throat - strep rash - vasculitis joint pains - vasculitis D&V - haemoptysis - ANCA associated vasculitis, goodpastures
eosinophllia on blood results can indicate what causes of AKI?
churg strauss
interstitial nephritis
initial investigations in AKI?
Us&Es (marker of renal function - Na, K, Ur, Cr)
FBC and coagulation screen (anaemia, clotting - deranged in sepsis)
urinalysis (haematoproteinuria indicates renal cause rather than pre-renal)
US (small size = chronic kidney disease, not acute)
immunology (ANA - lupus, ANCA - vasculitis, GBM - goodpastures)
protein electrophoresis and BJP
further treatment of AKI?
establish perfusion pressure (fluid resuscitation, inotropes/vasopressors)
treat underlying cause (antibiotics for sepsis etc)
stop nephrotoxic drugs
dialysis if patient remains anuric and ureamic
life threatening complications of AKI?
hyperkalaemia fluid overload (pulm oedema) severe acidosis uraemic pericardial effusion severe uraemia
what causes post-renal AKI?
obstruction
- stones
- cancers
- strictures
- extrinsic pressure
how is post-renal AKI treated?
relieve obstruction
- catheter
- nephrostomy
refer to urology if stenting needed
how does hyperkalemia present?
muscle weakness
arrhythmias
levels of hyperkalaemia?
normal = 3.5-5
hyperkalaemia = >5.5
life threatening = >6.5
possible ECG findings in severe hyperkalemia?
tall T waves
slow rhythm
absent P waves
wide QRS
how is hyperkalaemia managed?
cardiac monitor
protect myocardium = 10mls 10% calcium gluconate for 2-3 mins
move K+ back into cells = insulin (10 units) with 50mls 50% dextrose (30 mins), salbutamol nebuliser (90 mins)
prevent absorption from GI tract ( calcium resonium - not in the acute setting)
how is bicarbonate related to hyperkalaemia?
low bicarbonate = metabolic acidosis
metabolic acidosis can exacerbate hyperkalaemia
treated with sodium bicarbonate
4 urgent indications for haemodialysis?
hyperkalaemia (>7 or >6.5 and unresponsive to medical therapy)
severe acidosis (pH <7.15)
fluid overload
urea >40, pericardial rub/effusion
1.40 year old male presenting with general malaise & haemoptysis (Urea 28, Creatinine 600, elevated ant-GBM)?
goodpastures
25 year old IVDA found collapsed at home
rhabdomyolysis
. 82 year old man admitted with BP 70 30, T 39, pulse 140bpm, K+ 7.0, urea 48, Cr 789, CRP 250, CXR left basal consolidation
sepsis
72 year old man presenting with difficulty passing urine and reduced urine output
obstructive
which of the following drugs does not cause hyperkalaemia? spironolactone Ramipril amiloride furosemide atenolol
furosemide
80 year old male admitted with 4-5 day history of diarrhoea. On admission BP 80 40, pulse 30bpm. Bloods phone back: Na 135, K+ 8.0, Urea 50, Cr 1000, Bicarb 9
Which of the following drugs would you administer first?
A. insulin/dextrose
B. Sodium Bicarbonate
C. Salbutamol nebuliser
D. Calcium Resonium
E. Calcium Gluconate
calcium gluconate
why is trimethoprim avoided in AKI?
it causes hyperkalaemia and causes increase in creatinine
