AKI Flashcards
AKI - urine output categories
1) normal: >/= 1200mL/day
2) non-oliguria: > 500 mL/day
3) oliguria: < 500 mL/day
4) aliguria: < 50mL/day
AKI - lab values
1) increase SCr by >/= 26.5 micromol/L within 48 h
2) increase SCr to >/= 1.5x baseline within 7 days
3) urine vol < 0.5 mL/kg/h for >/= 6 hr
AKI - categories
1) stage 1
- SCr: 1.5 - 1.9 x baseline or >/= 0.3 mg/dL (26.5 micromol/L) increase
- urine output < 0.5 mL/kg/h for 6-12 hr
2) Stage 2
- SCr: 2.0-2.9x baseline
- urine output < 0.5 mL/kg/h for 6012 hr
3) stage 3
- SCr: 3x baseline or increase to >/= 4.0 mg/dL (353.6 micromol/L)
- eGFR for < 18 yo: < 35 mL/min/1.73m^2
- urine output < 0.3 mL/kd/h for >/- 24 hr or anuria for >/= 12 hr
AKI - pathophysiology - prerenal - general
kidney still working but drop in perfusion (hospitalised patient)
AKI - pathophysiology - prerenal - cause
1) vol depletion: internal bleed, GI loss (N/D), urinary loss (overdiuresis, DI), loss from third space (burn, peritonitis), decreased effective vol (cirrhosis), peripheral vasodilation (sepsis, drug)
2) reduced cardiac output: CHF, MI, pericardial tamponade, acute PE, sepsis
3) renal hypoperfusion: bilateral renal occlusion (thrombosis, emboli, stenosis), meds
AKI - pathophysiology - prerenal - renal & extra renal signals
- indicate contraction of circulating blood volume: compensatory mechanism to preserve blood vol
- mecahnisms:
1) Severe but reversible vasoconstriction to maintain BP
. decrease solute excretion
. increase tubular reabsorption of glomerular filtrate
2) stimulate thirst: increase fluid uptake
3) promote Na & H2O retention (prevent further drop in BP)
. reduce urine vol = oliguria
. highly concentrated urine (high SG) and low in Na (FeNa< 1%)
AKI - pathophysiology - prerenal - consequences
prolonged reduction in renal perfusion - progress to AKI & renal cell damage
AKI - pathophysiology - prerenal - diagnosis & evaluation
1) patient hist: GI loss, diuresis
2) physical exam: dehydration, orthostatic HTN (drop in pressure when sit up after lying/stand up), tachycardia, poor skin turgor
3) central venous pressure: heart vol status
4) urine test: SG, osmolarity
AKI - pathophysiology - prerenal - management
1) treat pre renal cause
2) vasopressor w fluid in patient w vasomotor shock
3) supportive care
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - non drug cause
1) ischaemia: hypotension, vasoconstriction
2) nephrotoxin: contrast dye, heavy metal, amphotericin B, aminoglycoside, organic solvent
3) endogenous toxin: Hb, myoglobin
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - radiocontrast media-induced ATN - general
dye used for diagnostic purpose
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - radiocontrast media-induced ATN - pathophysiology
alter renal haemodynamic, cause renal ischaemia, direct toxicity
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - radiocontrast media-induced ATN - identifying feature
progressive increase in SCr within 24-48h after contrast administration, peak within 5 days
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - radiocontrast media-induced ATN - risk factor
1) pre-existing renal disease/CKD
2) old
3) comorbidities: HTN, DM, CHF, metabolic-syndrome, pre-DM, hyepruricemia, respi condition
4) vold epletion, hypotension, haemodynamic instability
5) concomitant administration of nephrotoxin: discontinue
6) use high vol or ionic/hyper osmolar contrast media
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - radiocontrast media-induced ATN - prevention
1) lowest dose possible contrast medium in risk patient
2) iso/hypo osmolar contrast media
3) IV hdyration: 1 hr before & continue for 3-6 hr after
4) N-acetylcysteine: antioxidant, 600-1200mg PO BID pre & post procedure or higher dose/IV
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - Aminoglycoside (AG) induced ATN - types of AG
amikacin, gentamicin, tobramycin
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - Aminoglycoside (AG) induced ATN - pathophysiology
accumulate in renal cortex = tubular epi cell damage & obstruction
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - Aminoglycoside (AG) induced ATN - risk factor
1) elderly
2) CKD, renal disease, DM
3) vol depletion, hypotension, sepsis, shock, hepatorenal syndrome
4) concomitant nephrotoxin adminsitration
5) AG therapy > 3 day, multiple dose, high serum trough conc, recent AG therapy
- gentamicin > 2mcg/mL
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - Aminoglycoside (AG) induced ATN - prevention
1) lower drug exposure
2) only use AG as last line
3) extend interval in normal kidney func
4) further prolong dosing for CKD patient
5) TDM
- single dose > 48h
- multiple dose > 24h
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - Amphotericin B induced nephrotoxicity - general
fungicidal, standard for life threatening systemic mycoses
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - Amphotericin B induced nephrotoxicity - dose limiting nephrotoxicity
ischaemic injury: vasoconstriction of afferent arteriole = direct tubular/glomerular toxicity
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - drug cause - Amphotericin B induced nephrotoxicity - prevention
1) continuous infusion instead of 2-4h infusion
2) alternate dat dosing
3) lipid formulation
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - phases - initiating
- ischaemia/exposure to nephrotoxic agent
- PG protective role on renal autoregulation during vasoconstrictive insult
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - phases - oliguric phase - general
- lower urine vol than necessary to excrete nitrogenous waste product = accumulation of toxic products
- 1-2 wks
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - phases - oliguric phase - management
1) diuretics
- non oliguria less extensive damage, better able to maintain fluid/electrolyte balance = better prognosis
- frusemide, bumetanide, torsemide, ethacrynic acid (if sulfa llergy and anaphylactic to others)
- increase urine ourput, facilitate fluid management
- diuretic resistance in aggressive Na restriction
- avoid diuresis in early AKI
2) CCB: reverse renovascular constriction, increase renal blood flow & GFR
3) supportive management: water, Na, K, P, acidbase balance
4) nutrition, dose adjustment, short term dialysis
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - phases - diuretic phase
- identifying feature: sig increase in urine output (start to cutdown diuretic)
- gradual increase in renal blood flow & GFR followed by increase concentrating ability of tubules to reabsorb Na & concentrating urea
AKI - pathophysiology - intrinsic - Acute tubular necrosis (ATN) - phases - recovery phase
1) regenerate new tubular cell
2) continue increase diuresis
3) Azotemia resolve 5-60 days after onset
4) gradual incease GFR to normal
5) sometimes permanent loss in renal func (fibrosis/atrophy)
AKI - pathophysiology - intrinsic - Acute interstitial nephritis (AIN) - causes
1) infection (viral/bacteria)
2) immunologic response
- penicillin, cephalosporin, quinolone, sulfanoamide, rifampicin
AKI - pathophysiology - intrinsic - Acute interstitial nephritis (AIN) - identifying feature
1) lesion in interstitial comprised of monocyte, macrophage, T/B cell
2) increase SCr, eosinophilia, red rash all over body, fever, malaise
AKI - pathophysiology - intrinsic - Acute interstitial nephritis (AIN) - management
1) discontinue (prevent permanent fibrosis)
2) treat underlying infection
3) supportive care
AKI - pathophysiology - intrinsic - glomerular damage
1) SLE: lupus nephritis
2) rapidly progressive glomerulonephritis (GN)
3) poststreptococcal GN
AKI - pathophysiology - intrinsic - vascular damage
vasculitis, polyarteritis nodosa, haemolytic uremic syndrome, thrombotic thrombocytopenic purpura, accelerated HTN, emboli (thrombotic, atheroscelortic)
AKI - pathophysiology - post renal - general
mechanical obstruction of urine flow distal to renal parenchyma (bladder/ureteral level)
AKI - pathophysiology - post renal - causes
1) bladder obstruction: prostatic hypertrophy, infection, cancer
2) improperly placed catheter, anticholinergic
3) ureteral: Cancer w abdominal mass, retroperitoneal fibrosis, nephrolithiasis (Stone/crystal)
4) renal pelvis/tubules: nephrolithiasis (oxalate, uric acid)
AKI - pathophysiology - post renal - identifying feature
- anuria = complete obstruction
- polyuria = partial obstruction
- elevated BUN/SCr ratio (reabsorption of urea from stagnated urine)
AKI - pathophysiology - post renal - treatment
- relieve obstruction
- alpha blocker stimulate passage of ureteric stone
AKI - risk factor
1) > 60 yo
2) female
3) acute infection
4) pre-existing CVS/chronic respi disease
5) dehydration/vold epletion
6) pre-existing CKD -> AoCKD
AKI - clinical presentation
1) decreased urine output
2) dark pee
3) peripheral oedema
4) flank pain
5) lab abnormalities
- increase SCr, BUN, K
- metabolic acidossi
- urinalysis: cast/cell/crystal/WBC/RBC/protein, abnormal SG, fractional excretion of Na (FeNa), urine osmolarity
AKI - effects of NSAID/ACEi/ARB - normal condition
- afferent arteriole dilate (PG) = increase blood flow
- efferent arteriole constrict (AG II) = increase pressure
- combined to maintain hydrostatic pressure for filtration
AKI - effects of NSAID/ACEi/ARB - outcome
1) NSAID & calcineurin inhibitor inhibit PG = afferent arteriole vasoconstriction
2) ACEi/ARB = antagonise AGII effect = efferent arteriole vasodilation
AKI - FeNa eqn
FeNa (%) = (Ua/Sna divide by Ucr/Scr) x100
AKI - management of AKI
1) high risk: discontinue nephrotoxic agent, ensure vol status & perfusion pressure, monitor SCr & urine output, avoid hyperglycemia
2) stage 1: high risk stuff + non-invasive diagnostic workup, consider invasive ones
3) stage 2: stage 1 stuff + check for change in drug dosing, consider renal replacement, consider ICU admission
4) Stage 3: stage 2 stuff + avoid subclavian catheter if possible
AKI - supportive management
1) haemodynamic support, vol replacement
2) remove inciting agent
3) treat underlying disease/condition
4) remove cause of obstruction for postrenal AKI
5) remove cause of obstruction for postrenal AKI
AKI - maintain water Na balance
diuretics for fluid management
Na < 2-3 g/day
AKI - electrolyte & acid base management
- Na Bicarbonate/alkalinising agent
- dietary restriction, meds
AKI - glycemia control
- plasma glucose 6.1 - 8.3 mmol/L
- insulin therapy
AKI - nutritional support
- maintain calorie intake, minimise hypercatabolic state & increase rate of urea increase
- goal 20-30 kcal/kg/day
- protein:
1) non-catabolic AKI: 0.8-1 g/kg/day
2) dialysis: 1-1.5 g/kg/day
3) hypercatabolic/on CRT: up to 1.7g/kg/day