acute kidney injury Flashcards
what is AKI ?
a rapid deterioration of kidney function , which is a clinical consequence and not a diagnosis and is usually reversible
falling urine output
rising serum urea and creatinine
what do the causes of AKI fall into ?
pre renal causes ( reduced kidney perfusion )
renal causes or intrinsic causes
post renal causes
what are some of the pre renal causes of AKI ?
hypovolemia
hypotension
reduced kidney blood flow
severe oedema
which patients are at higher risk of developing pre renal AKI ?
older patients
atherosclerotic patients
diabetics
patients with pre existing kidney disease
what are the causes of hypovolemia ?
shock
what are the causes of reduced kidney blood flow ?
NSAIDs
ACE inhibitors
angiotensin II receptor blockers
abdominal aortic aneurysm
ace inhibitors
what effect do ace inhibitors have on the kidneys?
they inhibit efferent vasoconstriction
what effect do NSAIDs have on the kidneys ?
NSAIDs inhibit prostaglandins which in turn allow for afferent vasodilatation
what are the causes of renal AKI ?
glomerular disease which can either be : inflammatory or thrombotic tubular injury interstitial injury vascular injury
what are the causes of post-renal AKI ?
intrinsic and extrinsic
what are the intrinsic causes of post renal AKI ?
stone
blood clot
papillary necrosis
what are the extrinsic causes of post renal AKI ?
prostatic hypertrophy/malignancy
pelvic malignancy
retroperitoneal fibrosis
retroperitoneal fibrosis
what does acute tubular necrosis happen as a result off ?
any pre renal cause of AKI that reaches a point where autoregulation is no longer working - this will most probably lead to ischemic ATN
what are the four phases of AKI ?
onset phase
oliguric phase
diuretic phase
recovery phase
when does the diuretic phase of AKI happen ?
when the cause of the AKI is corrected
what is the clinical picture of each of the causes of AKI ?
- pre-renal causes - evidence of dehydration and hypovolemia , low BP and a rapid pulse
- post renal causes - evidence of renal colics with acute onset anuria and hematuria
- renal cause - history of nephrotoxic drugs intake, sepsis
what are the lab findings commonly found with hypovolemia ?
high levels of ADH , increased secretion from the pituitary gland
disproportionate rise in the plasma urea:creatinine ratio
disproportionate rise in plasma urea: creatinine ratio
how would we differentiate between AKI and CKD using US ?
CKD shows a shrunken kidney
except in patients with diabetes- who have normal sized kidneys even in disease
what investigation clues could indicate glomerulonephritis ?
hematuria
proteinuria
RBC casts
in what cases may we find eosinophilia ?
acute interstitial nephritis
cholesterol embolism
vasculitis
what does thrombocytopenia suggest ?
thrombotic microangiopathy
what is the management for AKI ?
conservative management
what is the management for hyperkalemia ?
urgently obtain a 12 lead ECG
- – if k> 7mmol give 10ml of 10% calcium gluconate IV and monitor every 10 minutes
- – if k>6.5mmol 10 units of actarapid in 100 ml of 20% dextrose over 15 minutes
- – if 6-6.5 mmol give calcium resonium 15g along with laxatives
what is the management for acidosis ?
consider giving 300-600 ml of isotonic sodium bicarbonate if venous bicarbonate is <22 mmol
what is the management for pulmonary oedema ?
give high flow oxygen
if haemodynamically stablee give furosemide
if haemodynamically stable give furosemide
if pulmonary oedema is very severe what is the best step in management ?
haemodialysis
haemofiltration
what are the indications of dialysis in AKI ?
1- persistent hyperkalemia
metabolic acidosis
volume overload (pulmonary oedema) that are not responding to treatment
2- uremic manifestations
3- fear of volume overload
4- toxin induced AKI
what is the mechanism of autoregulation of blood flow in the kidney ?
in cases of reduced blood flow to the kidney :
afferent vasoconstriction occurs by prostaglandins
efferent vasodilation occurs by action of angiotensin II
what is the clinical application off the autoregulation mechanism ?
NSAIDs inhibit prostaglandins which in turn inhibit vasodilation of the afferent arteriole
ACE inhibitors or ARBs inhibit angiotensin II which in turn inhibits the vasoconstrictive effect on the efferent arteriole
both mechanisms may be overcome by hypovolemia
kol dah under the umbrella off pre renal AKI
what is the cut off value in which autoregulation cannot be maintained ?
70 mmHg
what is oliguria ?
urine output less than 400 ml
what is theRIFLE criteria
risk
injury
failure
loss
end stage
uses an increase in serum creatinine or a decrease in urine output
which stage ar RRT patient considered to be at according to the AKIN criteria ?
stage 3
what are the LUTS ?
hesitancy
frequency
nocturia
palpable bladder
complete anuria
what do different measures of urea:creatinine ratio indicate ?
BUN:C of more than 20:1
or
U:C of more than 40:1 is indicative of pre-renal causes off AKI
ratios more than those indicate renal causes - renal tubular acidosis
What are the indications for a renal biopsy?
1: unexplained urine abnormalities
2: persistent ATN for more than 4 weeks
3: unclear etiology
4: suspicion of systemic disease
What are the characteristic findings in the urine analysis of drug-induced nephritis?
proteinuria
eosinophilia
bilateral crepitatiions in a patient with AKI ?
pulmonary oedema due to volume overload
what is the calcium homeostasis like in CKD ?
hypocalcemia
hyperparathyroidism
