AKI Flashcards
(43 cards)
criteria for an AKI?
KDIGO guidelines
1 of:
• ↑ creatinine >26 in 48 hours
• ↑ creatinine x 1.5 baseline in 1 week
• ↓ urine output <0.5 ml/kg/hr for 6 hours (8 in kids)
• (in kids: ↓ GFR 25 percent over 7 days)
aldosterone:
• where secreted and in response to what?
• where does it act?
• what does it do to Na+ and K+ levels?
- secreted in the adrenal cortex in response to low blood P.
- acts on the distal CT and collecting duct
- reabsorbs Na+ (and therefore H2O, ↑ BP), and exchanged for K+ (therefore ↓ K+ in blood)
ADH (vasopressin):
• where secreted?
• where does it act?
- posterior pituitary
* collecting duct to ↑ aquaporins, and ↑ H2O retention
renin
• where’s it from and what is it?
• how is it released? (3)
• how does it ↑BP
• juxtaglomerular cells (JGC) in kidneys, enzyme
• 1) baroreceptor mechanism when ↓ P. in afferent arteriole
2) SYMP nerve mechanism
3) macula densa mechanism which detects ↓ NaCl in distal CT and tells JGC to get a move on
• meets angiotensinogen (from liver), becomes angiotensin 1, meets ACE enzyme (from lungs), becomes angiotensin 2
ΔΔ causes pre-renal AKI?
- D + V, burns, pancreatitis
- shock, haemorrhage, sepsis, major surgery, MI
- ↓ CO (HF)
- hepatorenal syndrome
- DHx: NSAIDs, ACEi/ARBs, diuretics
what do NSAIDs do in AKI?
exacerbate by constricting afferent arterioles
what do ACEi and ARBs do in AKI?
dilate Efferent arterioles
what do diuretics do in AKI?
hypovolaemia
is there renal cell injury in pre-renal AKI?
no, reperfusion restores function
unless acute tubular necrosis from prolonged hypoperfusion
ΔΔ causes intrinsic AKI? (3)
1) glomerular:
• acute tubular necrosis (ischaemia)
• GN
2) interstitial:
• acute interstitial nephritis (allergy, infection, sarcoid)
3) vessels:
• vascilitis - afferent constriction (RAS, malignant HT, HUS, TTP, DIC, PET)
ΔΔ causes postrenal AKI?
- kidney stones
- catheter
- urethral strictures, CA
- BPH
- UTI
Hx: patient hasn’t passed much urine in last few days (<0.5/kg/hr), has developed SOB waking up in the night?
Ex: lung crackles and swollen ankles?
general Sx of AKI
Hx: patient not passing much urine, and is fatigued, with N, V, confusion?
uraemic Sx of AKI
Hx: patient has had 3 days of D+V, not passed much urine, is feeling dizzy upon standing?
Ex: marked diff in BP between sitting and standing, and tachycardic?
prerenal AKI
Hx: pregnant woman with headaches and changes in vision hasn’t passed much urine?
Ex: HIGH BP?
intrinsic AKI secondary to PET (microangiopathy, like HUS, TTP, etc)
Hx: patient with loin to groin pain, can’t sit still, and hasn’t passed urine in 24 hours?
postrenal AKI (kidney stones)
what is the polyuric phase?
- as the kidney heals from an AKI, the tubules regenerate but water concentration is the last function to return
- toxins accumulate in the kidney which increases the osmotic load
- = massive polyuria
- make sure enough IVT to replace!!!
nephrotoxic drugs? “FANG”
- Furosemide
- ACEi/ARBs
- NSAIDs
- Gentamicin
Ix AKI?
BEDSIDE: • ECG (K+) URINALYSIS • dipstick: blood + protein (GN, stones, UTI, Ca, trauma), microscopic blood (interstitial nephritis), wbcs (UTI, interstitial) • microscopy: red cell casts (rapid GN), eosinophils (interstitial), granular/tubular epithelial cell casts (acute tubular necrosis) • low Na+ (pre-renal) • myoglobinuria (rhabdomyolysis) • culture (infection) • immunoelectrophoresis (myeloma)
BLOODS:
• FBC: low Hb (CKD), wbcs (infection), eosinphilia (interstitial), low plts (HUS, TTP)
• U+E: high urea, creatinine, K+, check bicarb and Ca++
• LFTs (hepatorenal syndrome)
• coag: DIC (sepsis), weird clotting (CKD)
• CK (rhabdo)
• CRP (infection)
• ABG (metabolic acidosis)
+/-
• immune: ANCA, anti-GBM, ANA, anti-dsDNA, RF, etc
• electrophoresis (myeloma)
• culture (sepsis)
IMAGING:
• US: hydronephrosis (postrenal obstruction), small (CKD)
• +/- AXR, abdo CT
• CXR (pulmonary oedema)
Ix if suspicion of rapidly progressive GN or prolonged acute tubular necrosis?
biopsy
how to distinguish AKI from CKD?
- look at previous bloods
- see if GFR risen over 48 hours
- US shows small kidney in CKD
- nocturia in CKD
- shorter Sx, Hb and Ca++ normal, in AKI
- can be acute on chronic failure!
approach to managing AKI?
Ex for life-threatening complication:
• HR, BP, JVP, CRT
• VBG (K+)
• ECG (K+)
Fluids + monitoring
• 250-500ml bolus (<2 litres)
• fluid balance + catheter
• monitor K+, lactate, creatinine
Ix
• dipstick (pre-catheter)
• USS w/n 24 hours
• LFTs (hepatorenal)
• platelets +/- film for haemolysis (HUS, TTP)
• autoAb if indicated (IgG/A, ANA, ANCA, anti-GBM)
Tx:
• sepsis 6
• stop DHx
complications of AKI?
- metabolic acidosis
- high K+
- pulmonary oedema
when to give RRT (dialysis) in AKI?
“Ahhh FUK”
- Acidosis pH <7.1
- Fluid overload/pulmonary oedema
- Uraemia (Sx - pericarditis, encephalopathy)
- K+ >6.5 and refractory, ECG Sx
