AKI Flashcards
What is the definition of acute kidney injury?
a rapid (hours to days) decline in kidney function
What parameters are used to differentiate between different stages of AKI?
- creatinine increase
- urine output
What units are used for urine output?
ml/kg/hr
What units are used for creatinine?
μmol/L
What is the creatinine level increase for stage 1 AKI?
26μmol/L or 50-100% increase
What is the urine output for stage 1 AKI and in what timeframe?
<0.5ml/kg in 6 hours
What is the urine output for stage 2 AKI and in what timeframe?
<0.5ml/kg in 12 hours
What is the creatinine level increase for stage 2 AKI?
100-200%
What is the creatinine level increase for stage 2 AKI?
100-200%
What is the creatinine level increase for stage 3 AKI?
- > 354μmol/L increase (if baseline <310) OR
- > 200% increase OR
- needs dialysis
What is the urine out for stage 3 AKI and in what timeframe?
<0.3ml/kg in 24 hours OR anuric (needs dialysis) OR anuric for 12 hours
Which of the AKI stages shows the worst renal function?
stage 3
What is the mortality rate for hospitalised patients with AKI?
26.3%
AKI serum creatinine is used as measure of what?
function NOT eGFR
How does hospital/ITU stay change with worsening renal function?
increases
What are the 3 main risk factors for AKI?
- older age
- disease states
- drugs
What conditions are a risk factor for AKI?
- diabetes mellitus
- liver disease
- heart disease
- hypertension
- chronic kidney disease
What drugs are a risk factor for AKI?
- diuretics
- ACE inhibitors
- ARBs
- NSAIDs
- vancomycin
- gentamicin
What are the 3 categories of AKI causes?
- pre-renal
- (intra-)renal
- post-renal
What is pre-renal AKI caused by?
perfusion failure - blood flow to kidneys
What is intra-renal AKI caused by?
intrinsic disease of the kidney
What is post-renal AKI caused by?
urinary obstruction
What is the most common category cause of AKI?
intra-renal
What can cause the perfusion failure responsible for pre-renal AKI?
- hypovoloemia
- hypotension
- renal artery occlusion
What can cause hypovolaemia?
- diarrhoea
- vomiting
- haemorrhage
What drugs can worsen the perfusion failure responsible for pre-renal AKI?
- any drugs that block the RAAS system
- diuretics
- NSAIDs
- antihypertensives
What is meant by renal autoregulation?
the kidneys are able to maintain adequate perfusion and urine output despite an increase or decrease in blood pressure
When the BP and blood volume goes outside the range of renal autoregulation, what happens?
perfusion failure, as well as low urine output
diagram outlining how the RAAS system works
diagram should have:
- renin produced by juxtaglomerular cells of kidneys in response to low BP/salt depletion
- renin converts angiotensinogen to angiotensin I
- angiotensin I converted by ACE to angiotensin II
- ang II acts on brain to increase thirst, adrenal cortex to release aldosterone and vascular smooth muscle to cause vasoconstriction and efferent arteriolar constriction
- aldosterone acts on kidneys to increase Na retention and sodium excretion
- brain and kidney actions lead to increase in blood volume
- vascular smooth muscle actions lead to increase in blood pressure
What does ang II do to afferent and efferent arterioles of the kidney? What does this cause?
- causes vasoconstriction at efferent
- causes vasoconstriction at afferent (but stimulates release of vasodilator NO2 so it stays dilated)
–> increase in blood pressure
What do prostaglandins do to the afferent arterioles in the kidney? What does this cause?
- causes vasodilation
- causes an increase in kidney perfusion
Which do NSAIDs affect: the afferent arteriole or the efferent arteriole? What is the result?
- affect afferent arteriole
- block prostaglandin’s vasodilation of afferent arteriole
- leads to reduced kidney perfusion
Which do ACEi/ARBs affect: the afferent or efferent arteriole? What is the result?
affect on both….
AA: block prostaglandin’s vasodilation of afferent arteriole
- leads to reduced kidney perfusion
EA: stop the vasoconstriction of the efferent leading to a reduction in BP needed to for ultrafiltration of the kidneys
Why does RAAS blockade lead to AKI?
lack of ability to compensate for BP drop
Perfusion failure can have consequences on the kidney nephron. What is this consequence?
acute tubular necrosis
-when the cells in the kidneys are not getting enough nutrients or fluid, - very low BP, so suffer damage
can be drug related etc
What are the treatment options of perfusion failure?
treat underlying cause
- fluid volume replacement
- blood pressure support (inotropic drugs)
- restore arterial patency
- stop RAAS blockade
- stop NSAID
In what two ways can drugs be toxic to the kidneys? and cause AKI
- if their serum levels are too high: monitor!
- if they crystallise in the tubules
What drugs can be toxic by having their serum levels too high?
- gentamicin
- vancomycin
What drugs are toxic by being able to crystallise in the tubules?
- aciclovir (synthetic nucleoside analogues)
- indinavir
- sulfadiazine
IV, can cause nephrotoxicity quickly
What is nephrocalcinosis?
calcium and phosphate deposition in the kidneys
What can nephrocalcinosis be caused by?
- sodium phosphate enemas, infusions can cause a massive phosphate load
- OTC calcium antacids can deposit Ca and alkali
What would be seen on a nephrocalcinosis X-ray?
the kidneys (which normally wouldn’t be visible) clogged up with Ca and P deposits
What 3 drugs need monitoring in the context of AKI and why?
- gentamicin
- amikacin
- vancomycin
- they all have narrow therapeutic indexes and can damage the kidneys
aminoglycoside: given 1x daily, monitored diff to those
What are the adverse effects of gentamicin?
- epithelial necrosis
- glomerular toxicity
- vascular toxicity
What is interstitial nephritis?
how to treat/prevent?
the kidney having an ‘allergic’ reaction to a drug
unpredicatble but can prevent by cautious use. can cause AKI
What 5 drugs is interstitial nephritis common with?
- NSAIDs
- Proton pump inhibitors
- 5-aminosalicylates
- other antibiotics
- anti-retroviral drugs
What is metformin used to treat?
type 2 diabetes mellitus
How can metformin cause lactic acidosis?
- reduces gluconeogenesis
- decreased conversion of lactate to pyruvate
- leads to lactate build-up
Why should AKI patients not be treated with metformin?
damaged kidneys will not be able to remove lactate/pyruvate
What drugs have reduced clearance in AKI?
- penicillins
- opiates
- benzodiazepines
- insulin (can cause hypoglycaemia)
- aminoglycosides (increased tox and reduced clearance)
in AKI, how can insulin cause hypoglycaemia?
increased levels… inc hypogly event risk, short term harm
as kidneys usually excrete insulin
what else may lead to increased pyruvate (lactic acidosis and metformin)
sepsis
What are the causes of death in AKI?
- infection
- pulmonary oedema
- underlying disease
- hyperkalaemia
- acidosis
In dialysis, what may be removed/added from the patient’s blood?
fluids and solutes
Does dialysis occur inside or outside of the body? What special term is used to describe this?
- outside the body
- extracorporeal
What is dialysis?
an extracorporeal therapy where the patient’s blood and dialysis fluid is separated by a semi-permeable membrane
What is used between the patient’s blood and dialysis fluid in dialysis?
a semi-permeable membrane
How does the GFR rate compare between dialysis and the own kidneys?
dialysis is not as good as real kidneys; only has a GFR of <15mls/min
What determines the permeability of semi-permeable membranes?
- size of membrane
- charge of membrane
How do the semi-permeable membranes compare between haemodialysis and peritoneal dialysis?
haemodialysis: external device
peritoneal dialysis: peritoneum
What process determines how drugs are cleared?
diffusion: high to low conc
In peritoneal dialysis, what is used to gain entry into the abdomen?
a peritoneal catheter
How long is fluid left in before it’s drained in peritoneal dialysis?
30 mins
How is peritoneal dialysis performed?
- dialysis fluid inserted into abdomen via catheter
- fluid left to dwell for 30 min
- fluid drained into collection bag
How often a day can peritoneal dialysis be performed?
up to 20 times
Why is peritoneal dialysis favourable for some patients as opposed to haemodialysis?
can be done at home
Peritoneal dialysis can lead to the loss of what macromolecule? Why?
- proteins
- peritoneum allows albumin and other plasma proteins through
What are the two options for the time of day that peritoneal dialysis can be performed?
- continuous during the day
- overnight
How long does peritoneal dialysis last?
~8-10 years
What is there a risk of with peritoneal dialysis?
peritonitis
Haemodialysis and peritoneal dialysis both require permanent access to different parts of the body. What does haemodialysis require permanent access to?
the circulation
What are two possible ways permanent access to the circulation is gained in haemodialysis?
- AV fistula
- central venous catheter
How often is haemodialysis carried out and for what condition?
- 3x a week
- CKD5, or severe AKI
How long does each haemodialysis session last for?
4 hours
How long can haemodialysis last?
as long as there is permanent access to the circulation
Explain the journey of the blood in haemodialysis.
- leaves patient’s vein
- enters dialysis machine via blood pump
- thinned via heparin pump
- waste from the plasma leaves at dialysis filter
- dialysate fluid enters at dialysis filter
- blood re-enters patient’s vein
whats there a risk of with haemodialysis?
infection
Patients with what two conditions need dialysis?
- CKD
- AKI
What GFR in CKD the need for dialysis?
<10ml/min/1.73m^2
depends on symtoms and fluid volume control
Before what in patients with CKD is dialysis initiated?
before the patient becomes ill
What creatinine levels in AKI and level of urination is required to initiate dialysis?
> 500mcmol/L
- or oligo/anuric
= low urine output/ lack of urine produced
What condition due to AKI initiates dialysis?
what mat are complications of this? (2)
uraemia (buildup of toxins in your blood)
- pericarditis
- encephalopathy
The following signal the initiation of AKI if they’re not controlled medically. What are they?
- hyperkalaemia
- metabolic acidosis
- pulmonary oedema
Why does AKI cause hyperkalaemia?
treatment?
- reduced urinary excretion
- increased intracellular K+ release
want to improve K before dialysis.
if results in inc K, treat using insuling dextrose, dialyse after so K made safe.
In dialysis, what will the clearance of a drug depend on?
- nature of the drug: solubility, size, charge
- nature of the membrane: size, charge
- non-renal and renal metabolism
- type of dialysis
- duration of dialysis
- drug distribution
what should be done with metabolic acidosis- when its causing AKI?
when?
manage bicarbonate
IV/ orally
before dialysis
What is the drug class of vancomycin?
glycopeptide antibiotic
What type of therapeutic window does vancomycin have?
narrow
How much vancomycin is excreted unchanged by the kidneys?
90%
What is the half-life of vancomycin
a) normally?
b) in CKD5?
c) with no kidneys?
d) in haemodialysis?
a) 4-6 hours
b) 54-180 hours
c) 7.5 days
d) 6 hours (high flux) to 7 days (standard)
How do the plasma levels of vancomycin change during haemodialysis treatment?
they drop, maybe even below the MIC (minimum inhib conc)
- want ABOVE MIC, steady line
Dialysis helps to maintain the homeostasis of what? (3)
- fluid
- acid-base
- electrolyte
How/ when must vancomycin be dosed in haemodialysis?
it needs to be dosed after haemodialysis due to the plasma levels dropping after a session
dialysis access to circulation: 2 types?
Arterio-Venous Fistula
- Superficial vein used.
- Local/general anaethetic.
- 6 weeks for healing
Central venous catheter
- Risk of infection, thrombosis, sclerosis.
350ml/min or more capable
Diffusion in haemodialysis semi-permeable memb allows what?
equilibrium and transfer.
what does semi-permeable allow.
describe processes of blood movement and water?
(how is AMOUNT of water controlled)?
- blood cells and large components remain in blood
- Ultrafiltration- water removal
Water takes some solutes. Reduction of volume in patient circulation
Pressure gradient created: causes water movement. By changing this, can control HOW MUCH WATER removed
Acid load cant be removed by filtration alone, whats added to patient from dialysis soln?
what does it allow?
Alkali (buffer) added
o Conc of alkali greater than in plasma
o Alkalis used: bicarbonate, acetate, or lactate
o Acetate and lactate: metabolised to bicarbonate
Allows correction of metabolic acidosis
How to choose type of Dialysis
• Patient decision made on lifestyle factors
• Haemodialysis better for:
oDependant patients
oPatients who previously had peritoneal dialysis
Complications of ahemodialysis?
Repeated access to circulation and/or permanent intra-vascular catheters
- Increased risk of infection
Hypotension caused by rapid fluid removal
Vascular damage (central vein occlusion) caused by repeated access procedures
Risk of blood borne virus
- May be risk for patients dialysing on holiday outside UK esp. HBV endemic areas
