RENAL 227 Acute Renal Failure Flashcards
What is renal failure?
A failure of renal excretory function due to GFR depression. There is an abrupt deterioration in renal parenchymal function
What does the RIFLE criteria stand for?
Risk, Injury, Failure, Loss and End Stage Kidney Disease
it is criteria for each level
What factors affect outcome in ARF?
Age, DM, HTN, CCF, pre-existing renal disease and sepsis
What are some extra renal effects of ARF?
Pulmonary: Oedema and ARDS and Infection
CNS: Altered consciousness, coma, confusions and convulsions
CVS: HTN, pericarditis, arrythmia, hypertrophy, HF and MI
What is indicative of ARF in the blood?
Uraemia - high serum urea concentration
What can you group causes of ARF into?
Pre-renal
Intrinsic and Post-renal
What are the pre-renal causes of ARF?
impaired perfusion of the kidneys
e.g. hypovolaemia, hypotension, inefficient cardiac pump, vascular disease, third space sequestration, drugs
What drugs and why do certain drugs increase tendency towards pre-renal ARF?
ACEI and NSAIDS
because they impair autoregulation -
NSAIDS = constriction of afferent arteriole therefore not maintaining pressure difference/ inability to regulate flow through
ACEI = blocks efferent constriction
What is 3rd space sequestration?
Where ECF ends up in a place other than intravascular or interstitial space?
e.g:
severe pancreatitis –> retroperitoneal space
intestinal obstruction –> in GI tract
Crush injury –> into damaged muscle
Peritonitis –> into peritoneum
What is post-renal ARF?
ARF due to obstruction of the urinary tract from calyces to the external urethral orifice
What are the 3 main causes of Intrinsic AKI?
Acute tubular necrosis
Radiocontrast nephropathy
Acute tubulo-interstitial nephritis
Describe acute tubular necrosis?
Can be due to ischaemia or nephrotoxicity
Necrosis of tubular cells but they have the ability to regenerate but there is no current treatment
What are some causes of ATN?
Ischaemia: hypotension, hypovolaemia, shock, sepsis
nephrotoxiticity: aminoglycosides, radiocontrast, cisplatin, rhabdomyolosis
What are the risk factors for radiocontrast nephropathy?
pre-existing renal disease, DM
What happens in radiocontrast nephropathy?
There is transient vasodilation followed by prolonged vasoconstriction
How might you prevent radiocontrast nephropathy?
low osmolality contrast media, IV fluids, antioxidants, n-acetylcysteine, diuretics and NaCO3
What is acute-tubulo interstitial nephritis usually due to?
Drugs: penicillins, cephalosporins, sulfonamides, rifamipicin, furosemide and NSAIDS
Usually present with fever, rash, arthralgia, eosinofillia and a cellular infiltrate in the tubulointerstitium
What are the two main life threatening complications of ARF?
Metabolic acidosis and hyperkalaemia
How do you calculate the serum anion gap and what should it normally be?
cations - anions
Na+K -Cl-HCO3
should normally be 6-13meq/l
What does a normal anion gap in a metabolic acidosis indicate?
That HCO3 is being lost but replaced by CL- therefore no change
causes: ddiarrhoea, renal tubular acidosis
What does an increased anion gap in metabolic acidosis indicate?
increased acid production other than increased Cl-
e.g. lactic acidosis, DKA and renal failure
What is the clinical effect of a metabolic acidosis?
muscle weakness, altered mental states, kussmauls breathing, hyperkalaemia and hypotension
What is given cardioprotectively in hyperkalaemia?
IV Calcium gluyconate
What is the role oif IV dextrose insulin/ Beta agonists in treating hyperkalaemia?
Shifts potassium into the intracellular compartment
What is rhabdomyolosis?
Breakdown of muscle and release of these products into the circulation - these are harmful to the kidney (myoglobin, potassium, phosphate, urate and creatinine kinase)
What are some causes of rhabdomyolosis?
Crush injury, immobilisation, compartment syndrome, marathon runners, hypokalaemia, prolonged convulsions, hypothermia, alcohol, opiates, statins etc etc etc
What is the pathophysiology behind rhabdomyolosis?
Obstruction with haem pigment cast and proximal tubule injury by haem iron
10-12L of fluid may accumulate in damaged tissue withyin 24-48 hours
How do you diagnose rhabdomyolosis?
History, red brown urine, increased CK and LDH
hyper: K, PO4, uric acid
hypo: calcium (deposited in damaged muscle)
How do you treat/prevent rhabdomyolosis?
fluids to improve renal perfusion and urine output - wash out obstructions
forced diuressi but can worsen hypocalcaemia and be careful in those with limited renal function anyway
What might cause a hyponatraemia with high ADH?
Hypovolaemic states: diarrhoea etcc
hypervolaemia states: HF and liver cirrhosis
SiADH, MDMA and hypothyroid
Why does HF and cirrhosis result in a high ADH in hyponatraemia?
baroreceptors sense decreased perfusion pressure therefore increasing ADH release and RAAS system despite the excess fluid
a Na less than 125 is a poor prognostic factor in HF
What may cause a hyponatraemia with a low ADH?
renal failure (impaired free water excretion), polydipsia and beer drinking
How do you calculate serum osmolality?
(2x serum [Na]) + serum glucose +plasma urea
What is osmotic demyelination syndrome?
due to rapid correction of severe hyponatraemia (
