AKI Flashcards
What is the Cockcroft gault equation
In the bnf page 22
Limitations of the Cockcroft gault equation
Inaccurate in oedema and extreme body weight
Not expressed using standardised reference values
Not validated in paediatric populations
Over estimation of GFR in severe Renal impairment
Limitations of mdrd
Only validated for Africans and Caucasians
Not validated in pregnancy
Inaccurate in extreme body weight
Less accurate where eGFR value more than 60ml per min
What are the risk factors of AKI
previous aki
Age more than 65
CHF
Liver disease
What are pre renal causes of AKI
Hypertension
Atherosclerosis
AHF
MI
What are the intrinsic causes of AKI
Tubular damage
Glomerular damage
Interstitial damage
What are post renal causes of AKI
Bladder stones
Blocked urinary catheter
Prostate cancer
What are the consequences of AKI
Loss of plasma proteins
Inability to excrete hydrogen
Inability to secrete potassium
Accumulation of waste
What is the management of AKI
Determine the cause (ie. Post renal pre renal etc).
Monitoring of HR, urine output etc
Correction of hyperkaelemia
Nutritional support
What to do when a patient has hyperkaelaemia and AKI
Stop all medication causing hyperkalaemia
How is the mdrd and CG different?
Mdrd assumes everyone has a body surface of 1.73m2
How to treat hyperkaelaemia
Ion exchange resins
Calcium gluconate- prevents cardiac arrest
Insulin - moves potassium
Why can’t nitrofurantoin be given in Aki and egfr of less than 45
Because it targets uti which is after the kidney so won’t get past or work
What is acute kidney injury?
A reversible decrease in glomerular filtration rate
What are the main causes of AKI
Pre renal: Before kidneys
Intrarenal: within kidneys
Post renal: after kidneys
What are the causes of pre renal AKI
- Sudden or severe drop in BP (hypotension)
- Flow obstruction in kidneys (atherosclerosis or renal artery stenosis)
3)
What are the causes of intrarenal AKI?
-direct damage to kidneys
-inflammation
- infection
- drugs
- autoimmune disease
- acute tubular necrosis
What are the causes of post renal AKI?
- obstruction of urine flow
-kidney stones
-bladder injury
-benign prostatic hyperplasia
What is the most common cause of AKI
Intrarenal
What does GFR stand for
Glomerular Filtration Rate
- the rate at which the glomerulus filters the blood
What is the role of the afferent arteriole?
Carries blood from the renal artery and this blood will be filtered in the glomerulus in the bowman’s capsule
What is the role of the efferent arteriole?
1.Remaining blood will exit out of the efferent arteriole.
2. The efferent arteriole is situated around the nephron as the vasa recta
3. The vasa recta role is to reabsorb things from the filtrate in the nephron and secrete toxins it doesn’t need
4. It will then join with the Renal vein
What is the filtrate that comes out the nephron?
Urine output
What can post and pre renal AKI cause?
Intrarenal issues
Why is there a decrease in gromelular rate?
- vascular changes
-vasoconstriction
-endothelial dysfunction - tubular changes
- damaged cells
-necrotic debris
Causes backleak of urine
How do you diagnose AKI
-Measure the amount of waste product called creatinine. This because high creatinine levels in the blood show filtration is not working effectively
What drugs are contraindicated in AKI
Remember “ DAMN”
Diuretics
Ace- inhibitors/ ARBS
Metformin
NSAID’s
What is creatinine
Normal breakdown product of creatine , which is released from muscle tissue.
- freely filtered by glomerulus
- not reabsorbed
- it is secreted
What is a recent way to measure creatinine clearance (apart from cockgrauft)
Modification of Diet in Renal Disease
(MDRD)
What are the symptoms of AKI
Vomiting/diarrhoea
Reduce urine production
Nausea
Fatigue
Confusion
Diagnosis of AKI
1) increase in serum creatinine of 26 micromol/L in 48 hours
2) Increase in serum creatinine of 1.5x of baseline in 7 days
Clinical tests for AKI
1) serum creatinine testing
2) urine production
3) urea and electrolytes
Treatment of AKI
1) IV fluid resuscitation
2) withhold nephrotoxic medication (DAMN)
Things to take into consideration in AKI
-If patient has been treated with trimethoprim, this can cause a false positive result as it increases creatinine
- recent given birth: can cause false positive due to rise in creatinine
For a person with AKI, assess:
Fluid intake and losses
Heart rate/ blood pressure
Changes in urination pattern
What is the mdrd used to calculate?
eGFR the glomerular filtration rate
What is the CG equation used to estimate?
Creatine clearance
What is MDRD adjusted for
Age
Gender
Race
NOT WEIGHT
What does the MDRD assume
That a normal body surface area is 1.73m2
Which equation is better for estimating drug dosing?
Recommended to use CG equation
Can you still use egfr (MDRD)for drug dosing
Yes
In which cases should eGFR not be used for calculating drug doses:
-Patients with extremes of body weight or muscle mass
- Renally cleared drugs with narrow therapeutic index (digoxin, DOACS, theophylline, lithium and vancomycin)
- rapidly changing renal function e.g AKI
What are the units for eGFR (MDRD formula)
- should always be a whole number (round to nearest whole )
- ml/min/1.73m2
Complications of AKI
Hyperkaelaemia
Metabolic acidosis
Sodium imbalance
Management of AKI
Determine AKI (post renal etc.)
Correct any hyperkaelaemia and / or metabolic acidosis
Optimise fluid balance
How to optimise fluid balance?
-hypovolaemia (sodium chloride 0.9%)
- hypernatraemia (dextrose 5%)
How to treat hyperkalaemia in AKI?
STOP all drugs that cause hyperkalaemia e.g ACE- inhibitors, ARBs, aldosterone antagonists
How to adjust drug dose in AKI
Reduce dose - causing drug concentration to return to desired level.
Increase dose interval - skipping every other dose causing drug conc to fall to desired level
Ways to prevent AKI
Maintain adequate systolic BP and hydration
Avoid nephrotoxic drugs
Monitor renal function and adjusting drug treatment
What is the drug “sick day” guidance
Advising temporary cessation of drugs that have potential to impair renal function when patients at risk of AKI
E,g ACE- inhibitors, ARBs, Diuretics , NSAID’s
