AKI (Acute Kidney Injury) Flashcards
3 Defining Characteristics: AKI
- ) Rapid decline in GFR
- ) Fluid, electrolyte, acid/base disruption
- ) Nitrogenous waste accumulation (azotemia)
* *azotemia: LOOK AT BUN
KDIGO: AKI Definition
- ) Increase SCr ≥ 0.3mg/dL in 48hr from baseline
- ) Increase SCr ≥1.5mg/dL in 7d from baseline
- ) Urine volume ≤0.5mL/kg/hr for 6hr
Azotemia
Increase in BUN and SCr
*seen in a blood test (typically)
Uremia
Azotemia + Clinical S/Sx
- ) N/V
- ) Decreased platelet aggregation (“uremic bleeding”)
- ) Encephalopathy
- ) Pericardial effusion
Output Definition: Anuria
Output Definition: Oligonuria
≤500mL/day
Output Definition: Non-oligonuria
> 500mL/day
AKI Classifications (3)
RIFLE (Risk, Injury, Failure, Loss, ESKD)
AKIN (Stage 1-3)
KDIGO (Stage 1-3)
RIFLE Category Criteria: R
R = Risk
SCr Criteria:
Increase 1.5x from baseline OR >25% GFR DECLINE from baseline
Urine Criteria:
RIFLE Category Criteria: I
I = Injury
SCr Criteria:
Increase 1-2x OR >50% GFR DECLINE from baseline
Urine Criteria:
RIFLE Category Criteria: F
F = Failure SCr Criteria: SCr increase 3x OR GFR DECLINE >75% from baseline OR SCr ≥4mg/dL with acute increase ≥0.5mg/dL Urine Criteria: ANURIA ≥ 12hr
RIFLE Category Criteria: L
L = Loss SCr Criteria: Complete loss of Fx Urine Criteria: N/A
RIFLE Category Criteria: E
E = ESKD SCr Criteria: RRT > 3months (renal replacement therapy) Urine Criteria: N/A
AKIN: General Characteristics (3)
- ) Defines AKI as “abrupt decrease in kidney Fx” (≤48hr)
- ) NO GFR calculation included in staging
- ) FLE (from RIFLE) included in AKIN Stage 3
AKIN: Stage 1
SCr Criteria:
SCr ≥ 0.3mg/dL OR 1.5-2x from baseline
Urine Criteria:
AKIN: Stage 2
SCr Criteria:
2-3x increase from baseline
Urine Criteria:
AKIN: Stage 3
SCr Criteria:
>3x increase from baseline OR ≥4mg/dL with acute increase of ≥0.5mg/dL, or RRT
Urine Criteria:
KDIGO: Stage 1
SCr Criteria:
Increase ≥0.3mg/dL or 1.5-1.9x from baseline
Urine Criteria:
KDIGO: Stage 2
SCr Criteria:
Increase 2-2.9x from baseline
Urine Criteria:
0.5mL/kg/hr ≥12hr
KDIGO: Stage 3
SCr Criteria:
SCr increase 3x from baseline, or SCr ≥4mg/dL, or need of RRT, or eGFR
AKI: General Management (7)
- ) Hemodynamic Stability
- ) Fluid Management
- ) Electrolyte management
- ) Renal perfusion
- ) Hydration
- ) Eliminate nephrotoxins (if possible)
- ) Renal Replacement Therapy (RRT)
KDIGO: AKI Stage 1
- ) Non-invasive diagnostic workup
2. ) Consider invasive diagnostic workup
KDIGO: AKI Stage 2
Stage 1+
- ) Check for drug-dosing changes
- ) Consider RRT
- ) Consider ICU admission
KDIGO: AKI Stage 3
Stage 1 ,2 +:
Avoid subclavian catheters (if possible)
AKI Types + Mortality Rates (3)
Community-acquired AKI (n/a)
Hospital-acquired AKI (15-40%)
ICU-acquired AKI (30-90%)
CA-AKI: Risk Factors (5)
- ) Chronic co-morbid conditions
- ) Elderly
- ) Male
- ) Sepsis/infection
- ) Drugs (ACEi, arbs, diuretics)
HA-AKI: Risk Factors (6)
- ) Volume depletion
- ) Hypotension
- ) Sepsis
- ) Low cardiac output
- ) Nephrotoxic drugs
- ) Radiocontrast dyes
ICU-AKI: Risk Factors (6)
- ) Septic shock
- ) Major surgery
- ) Multi-organ failure
- ) Hypotension
- ) Low cardiac output
- ) Nephrotoxic drugs
AKI Etiologies (3)
- ) Pre-renal (glomerulus, arterioles) 70% Cases
- ) Intrinsic (PCT, LH, DCT, CT(s)) 25% Cases
- ) Post-renal (bladder, ureter) 5% Cases
Post-Renal AKI: Causes (2)
Bladder outlet obstruction
Ureteral obstruction
Post-Renal AKI: Labs + Urinalysis (4)
- ) BUN : SCr ~ 15
- ) Urine cellular debris
- ) Urine : serum osmolality
FeNa: Equation
Fractional Excretion of Sodium (limited usefulness with diuretics)
100 x [(Urine sodium x SCr) / ( Urine creatnine x Serum sodium)]
Post-Renal AKI: Management
- ) Obstruction removal
- ) Alpha-1 blockers (BPH)
- ) Catheterization
- ) Percutaneous nephrostomy
Pre-Renal AKI: Causes
- ) Hypoperfusion
- ) Volume depletion (hemorrhage, vasodilation (sepsis), diuretics, nephrotic syndrome/cirrhosis)
- ) Decreased CO (cHF, MI, PE)
- ) Fx changes (reduced intraglom. pressure)
Pre-Renal AKI: Clinical Features
- ) Volume depletion evidence
* thirst, hypotension, tachycardia - ) Decreased perfusion volume evidence
* ascites, edema - ) Severe infection
* fever, hypotension, blood culture + - ) Nephro-toxic drugs (NSAIDs, ACEi, diuretics)
Renal Dynamics + ACEi Effects
Prostaglandins/COXs vasodilate AFFERENT
Angiotensin II constricts EFFERENT arteriole
Drop in intraglomerular pressure due to ACE inhibition
Pre-Renal AKI: Labs + Urinalysis (4)
- ) Normal urine sediment (NO CASTS)
- ) Urine:Serum osmolality > 1.5
- ) BUN : SCr > 20
- ) Low FeNa (
Pre-Renal AKI: Management (4)
- ) Restore renal blood flow by increasing intravascular volume
- ) Hemorrhage –> packed RBCs
- ) Plasma loss (burns) –> NS
- ) Increase CO –> positive ionotropes, intra-aortic balloon pump
Intrinsic AKI
Intra-kidney damage
- vascularture
- glomerulus
- tubules
- interstitium
Intrinsic AKI: DI Causes
- ) Glomerulonephritis (NSAIDs)
- ) Hemolytic uremic snydrome/TTP (clopidogrel)
- ) Allergic interstitial nephritis (ABXs)
Intrinsic AKI: Tubular Damage
MAJORITY OF CASES (85%)
- 50% –> pre-renal ischemia
- 35% –> direct tubular toxins
Intrinsic AKI: Causes + Drugs (6)
- ) ACUTE TUBULAR NECROSIS (ATN)
* post prerenal ischemic insult - ) Nephrotoxins (radiocontrast dyes, aminoglycosides (STAG), etc.)
- ) Rhabdomyolysis (statins)
- ) Hemolysis (carbidopa)
- ) Tumor Lysis Syndrome (chemotherapy)
- ) Ethylene glycol/methanol ingestion
Post-Ischemic ATN: Pathophys
Prolonged Ischemia resulting in renal damage (parenchyma)
Severe renal hypoperfusion may result in permanent failure
Post-Ischemic ATN: Phases
S/Sx similar to prerenal failure (does NOT resolve with fluid replacement therapy)
- ) Oliguric/initiation
- ) Diuretic/maintenance
- ) Recovery
Phases of ATN: Oliguric/Initiation Phase
1-2 Week Duration
- tubular cell death
- diminshed urine output (
Phases of ATN: Diuretic/maintenance
- Indicates initial kidney recovery
- increased urine output
- GFR increases gradually
- Na reabsorption/urine concentration increases
Phases of ATN: Recovery
- azotemia (5-60d resolution)
- urine concentration within months
- 90-95% GFR return to baseline
- 50% return of baseline (if initial baseline is poor)
Post-Ischemic ATN: Labs/urinalysis
- ) Muddy brown urine
- ) Granular/epithelial cell casts
- ) U/S osmolality 2%
- ) High [Mg++] + tubular enzymes
Post-Ischemic ATN: Management
Improve urine output
Restore kidney Fx
Decrease need for RRT
Improved survival
AKI: Complications
- ) Volume overload
- ) Edema
- ) Metabolic acidosis
- ) Malnutrition
- ) Drug-adjustments
Volume Overload: Management
- ) Fluid restriction
- ) Diuretics
- ) Limit Na-intake (DASH diet)
- ) Dopamine
PK: Loop Diuretics
Furosemide (2-2.5hr) RENAL ELIMINATION
glucouronidated
Bumetanide (2-2.5hr) HEPATIC ELIMINATION (P450)
Torsemide (6hr) HEPATIC ELIMINATION (P450)
Ceiling Dose: Furosemide
IV: 160-200mg (q6h)
PO: >200mg (?)
Ceiling Dose: Bumetanide
IV: 8-10mg (q6h)
PO: 8-10mg (QD)
Ceiling Dose: Torsemide
IV: 50-100mg (q12h)
PO: 50-100mg (QD)
TZD Synergy Doses (2 Rx)
HCTZ (CrCl-based):
> 50mL/min —> 25-50mg QD
25-50mL/min –> 50-100mg QD
100-200mg/day
Metolazone
5-10mg QD