kidney Flashcards
what is acute kidney injury (AKI)?
AKI is an abrupt and rapid decline in renal function occurring over hours to days, marked by an increase in serum creatinine and/or a reduction in urine output.
AKI is secondary to an acute event that compromises normal kidney function.
what is GFR?
glomerular filtration rate - a measure of the rate at which kidneys filter; measure of the excreting function of the kidney
what is the function of the kidneys?
regulate salt and water balance (reabsorb)
regulate blood pressure (renin-angiotensin system)
regulation of acid-base balance
eliminate waste products inc urea and creatinine from nitrogenous metabolism
produce erythropoietin needed for stimulation of erythrocyte production
activates vit D
metabolises insulin
normal urine output: 800-2000 mLs in 24 hrs
why is AKI considered a significant health issue?
associated with high morbidity (100 k annually), increased overall mortality, and a greater risk of progression to chronic kidney disease (CKD) and end-stage renal disease
what is a normal eGFR?
greater than 90 mL/min/1.73 m2
however values as low as 60 considered normal if no other signs of impairment
below 60 = impairment
below 15 = kidney failure
how is AKI diagnosed?
blood test: measuring serum creatinine levels and monitoring urine output
what are the symptoms of CKD?
- HTN
- fluid overload
- electrolyte imbalance (↑K+, ↑PO4, ↓Ca2+, ↓HCO3)
- metabolic acidosis
- anaemia
- uraemia
- vitamin D deficiency
- CKD mineral bone disorder (↑PO4, ↓Ca2+, ↑PTH) - like a jelly baby
CKD is insidious and a one way ticket
AKI is due to acute insult and can be overcome
what are the symptoms of AKI?
depends on cause!
dehydration: decreased urine output, drowsiness, confusion (toxins accumulate)
volume overload: SOB, fatigue, chest/abdominal pain, swelling in legs/ankles (fluid goes to lowest points - could be bum if lying down)
general symptoms seen in both: hyperkalaemia, uraemia, metabolic acidosis
what are the three main categories of causes for AKI?
pre renal : sudden serious drop in blood flow to kidneys
renal: damage from some meds, poisons, or infections
post renal: sudden blockage that stops urine from flowing out of
the kidneys
what are examples of pre renal causes?
hypovolaemia: haemorrhage, low BP, GI losses (diarrhoea), burns
hypotension (decreased blood flow to kidneys - need 25% cardiac output)
sepsis: toxins cause vasodilation which crashes BP (secondary to sepsis = AKI)
what are examples or renal causes?
prolonged hypoperfusion causing tubular injury
(ischaemia, myeloma, haemolysis [if RBCs lyse can block blood supply to kidneys] & rhabdomyolysis)
glomerular (glomerulonephritis and post-infectious)
autoimmune disease
drugs, e.g., aminoglycosides, cisplatin, NSAIDs, ACEi
what are examples of post renal causes?
pelvic masses, e.g. cervical cancer
prostatic hypertrophy/cancer
bladder tumour
renal stone disease
surgery
what are the risk factors for developing AKI?
old age ≥ 65years
being hospitalised, especially in intensive care
peripheral vascular disease
heart failure
diabetes mellitus
liver disease
history of urological obstruction.
history of AKI or CKD
sepsis
dehydration
dugs (NSAIDs, ACEIs, ARBs, diuretics)
contrast media (cleared by kidneys)
what is the pharmacological management of AKI?
no drug Tx!
treat the underlying cause
treating complications
supportive measures
what can be done for pre renal AKI?
restore circulating volume w IV fluids
what can be done for AKI caused by sepsis or lower urinary tract obstruction?
sepsis: antibiotics
lower urinary tract obstruction: catheter or nephrostomy - bypass obstruction to allow filtering
what complications may be linked to AKI and how can these be treated?
correcting electrolyte and fluid balance:
IV fluids
for hyperkalaemia: insulin/dextrose or K+ binders
manage sepsis: antibiotics
correct acidosis: IV sodium bicarbonate
hold nephrotoxic drugs (DAMN)
dialysis to remove toxins from blood
how does insulin/dextrose work?
insulin pushes glucose into cells
when glucose goes into cells, takes K+ with it (intracellular ion)
in hyperkalaemia - dose of insulin will shove K+ into cells (also blood glucose = hypo - so have to give dextrose to keep sugars up)
when is dialysis indicated in AKI?
- when uraemia is present
- fluid retention leading to pulmonary oedema
- severe hyperkalaemia
- severe renal failure
which drugs impair renal function?
Diuretics
ACEi/ARBs
Metformin
NSAIDs
aminoglycosides, contrast media
which drugs can cause other serious side effects in renal impairment?
metformin - can cause lactic acidosis in those w eGFR less than 30
opiates - can cause heavy sedation and respiratory depression as in RI metabolites cannot be excreted so accumulate
which drugs are actually nephrotoxic?
NSAIDs
MTX
contrast media
aminoglycosides
how can furosemide be used to check the severity of AKI?
loop diuretic - need to ensure patient has fluid (euvolaemic) - if dry then will not work (diuretics only work on intravascular compartment)
give dose of furosemide - if pass fluid then AKI not too bad - indication that kidneys will respond to diuretic
if no response - glomeruli not working - STOP furosemide
how can a pharmacist prevent AKI?
- withhold medications that may exacerbate AKI
- treat infections promptly
- ensure adequate hydration
- monitor blood tests for kidney recovery (creatinine)
- refer to specialists for unclear or severe cases
