Transcript Acute Renal Failure (ARF)

Acute Renal Failure (ARF)
Acute Kidney Injury (AKI)
Mitra Basiratnia
Ped Nephrologist
SUMS
AKI
• Formerly referred to as acute renal failure
• Abrupt reduction in kidney function measured
by decline in GFR
• Results in disturbances
– Impaired nitrogenous waste excretion
– Loss of H2O & electrolyte regulation
– Loss of acid-base regulation
• Contributing factor in morbidity & mortality
of critically ill
The pRifle Criteria
Risk
Increased creatinine × 1.5
or GFR decrease > 25%
Injury
Failure
Loss
Endstage
Increased creatinine × 2
or GFR decrease > 50%
UO<0.5 ml/kg/hr × 8 hours
UO <0.5 ml/kg/hr × 16 hours
Increased creatinine × 3 or GFR decrease
UO < 0.3 ml/kg/hr × 24 hours
>75% or creatinine > 4 mg/dL
or anuria × 12 hours
(acute rise >0.5 mg/dL)
Persistant AKI = complete loss of renal function > 4 weeks
End-stage kidney disease
Bellomo et al. Crit Care 2004;8:R204-R212.
Azotemia is a consistent feature of acute
renal failure (ARF), oliguria is not.
anuria ::: urine output < 0.5 ml/kg/h
Oliguria ::: urine output< 1 ml/kg/h
acute renal failure: common clinical features
• azotemia
• hypervolemia
• electrolytes abnormalities:
 K+
 phosphate
 Na+
 calcium
• metabolic acidosis
• hypertension
• oliguria - anuria
acute renal failure: classification
• Prerenal (hypoperfusion)
• Renal (intrinsic)
• Postrenal (obstructive)
prerenal
• decreased perfusion without cellular injury
• renal tubular and glomerular functions are intact
• reversible if underlying cause is corrected
prerenal
• common etiologies:
– dehydration
– hypovolemia
– hemodynamic factors that can compromise
renal perfusion (CHF, shock)
Sustained prerenal azotemia is the main factor
that predisposes patients to ischemia- induced
acute tubular necrosis (ATN)
postrenal
• obstruction of urinary tract
• important to rule out quickly:
– potential for recovery of renal function is often
inversely related to the duration of the obstruction
renal
• classified according primary site of injury:
–
–
–
–
tubular
interstitium
vessels
glomerulus
Clinical Approach to AKI:
Pre-, Intra-, and Post-Renal
Urinalysis Normal
History
Volume status
Ultrasound
Urinalysis
US shows
Hydronephrosis
Urinalysis
Abnormal
Post-Renal
Pre-renal
Tubulointerstial
Disorders
Glomerular and
Vascular Disorders
Nephrologists Clinical Approach to AKI
History
Volume Status
Ultrasound
Urinalysis
Normal Urinalysis
Pre-Renal
Low ECF Volume
GI losses
Hemorrhage
Diuretics
Osmotic diuresis
Abnormal urinalysis
Altered renal blood flow
or hemodynamics
Sepsis
Heart failure
Cirrhosis/Hepatorenal syndrome
Hypercalcemia
Medications
NSAIDs/Cox-2 inhibitors
ACE inhibitors
Angiotensin II receptor blockers
Vascular disease
Renal parenchymal disorders
Tubulointerstitial
Disorders
Glomerular
Disorders
Acute interstitial nephritis
Tubular obstruction
Acute
tubular
necrosis
Medication-induced
Crystals
Ischemic
Autoimmune
Calcium oxalate
Nephrotoxic
Sjogren
syndrome
(Ethylene glycol,
Contrast-induced
Sarcoidosis
orlistat)
Rhabdomyolysis
Infection-related
Indinivir
Acyclovir
Methotrexate
Tumor lysis syndrome
Myeloma cast
nephropathy
Hydronephrosis
Vascular Disorders
Post-Renal
Arterial
Prostate disease
Renal artery stenosis
BPH
Renal artery thromboembolism
Cancer
Fibromuscular dysplasia
Pelvic malignancy
Takayasu arteritis
Stones
Medium vessel
Stricture
Polyarteritis nodosa
Retroperitoneal fibrosis
Kawasaki disease
Small vessel
Glomerulonephritis
Thrombotic microangiopathies
Cholesterol emboli
Renal vein
Renal vein thrombosis
Abdominal compartment syndrome
acute renal failure: diagnosis
• History and Physical examination
• Blood tests : CBC, BUN/creatinine, electrolytes, uric acid,
CK
• Urine analysis
• Renal Indices
• Renal ultrasound (useful for obstructive forms)
• Doppler (to assess renal blood flow)
• Nuclear Medicine Scans
DMSA: anatomy
DTPA and MAG3: renal function, urinary
excretion and upper tract outflow
Presentation: Children
• History:
– AGE, hemorrhage, sepsis, decreased oral intake
– Bloody diarrhea w/ oliguria (<500ml/1.73m2/day) or anuria –
HUS
– Pharyngitis or impetigo – PIGN
– Hemoptysis and renal impairment – Pulm-Renal Syndrome
(Wegner’s, Goodpasture’s)
– Trauma/crush injury – rhabdomyolysis
– Exposure to nephrotoxins – aminoglycosides, amphotericin-B,
chemotherapy Rx
• PxEx:
– Tachycardia, dry MM, sunken eyes/fontanel, orthostatic BP,
decreased skin turgor
– Edema – nephrotic syndrome, heart failure, liver failure
– Skin findings – purpura, petechiae, malar rash, maculopapular
– HSP/SLE, AIN
renal indices
Reabsorption of water and sodium:
- intact in pre-renal failure
- impaired in tubulo-interstitial disease and ATN
Since urinary indices depend on urine sodium
concentration, they should be interpreted cautiously if
the patient has received diuretic therapy
renal indices
Fractional Excretion of Na (FENa)
FENa:
[ urine Na/serum Na]
[urine creatinine/serum creatinine]
x 100 %
prerenal azotemia:
– Urine sediment: hyaline and fine granular casts
– Urinary to plasma creatinine ratio: high
– Urinary Na: low
– FENa: low
Increased urine output in response to hydration
• renal azotemia:
– Urine sediment: brown granular casts and tubular
epithelial cells
– Urinary to plasma creatinine ratio: low
– Urinary Na: high
– FENa: high
Urine Sediment
Monomorphic RBCs
RBC cast
Dysmorphic RBCs
Hyaline cast
Urine Sediment
WBC cast
Fatty cast ATN
RTE cast
urine and serum laboratory values
Prenal
Renal
BUN/Cr
>20
<20
FeNa
<1%
>1%
RFI
<1%
>1%
UNa (mEq/L)
<20
> 40
Specific gravity
high
low
hemoglobinuria + myoglobinuria
hemoglobinuria:
transfusion reactions, HUS
myoglobinuria:
crush injuries, rhabdomyolisis
urine (+) blood but (-) red blood cells
 CPK  K+
treatment
aggressive hydration + urine alkalinization
mannitol / furosemide
acute renal failure: management
• treat the underlying disease
• strictly monitor intake and output (weight, urine output,
insensible losses, IVF)
• monitor serum electrolytes
• adjust medication dosages according to GFR
• avoid highly nephrotoxic drugs
• attempt to convert oliguric to non-oliguric renal failure
(furosemide )
acute renal failure: fluid therapy
If patient is fluid overloaded
• fluid restriction (insensible losses)
• attempt furosemide 1-2 mg/kg
• Renal replacement therapy
If patient is dehydrated:
• restore intravascular volume first
• then treat as euvolemic (below)
If patient is euvolemic:
• restrict to insensible losses (30-35 ml/100kcal/24
hours) + other losses (urine, chest tubes, etc)
sodium
• most patients have dilutional hyponatremia
which should be treated with fluid
restriction
• Na< 120mEq/L or symptomatic: hypertonic
saline
potassium
Oliguric renal failure is often complicated by hyperkalemia,
increasing the risk in cardiac arrhythmias
K>6 resin
K>7 emergency treatment
Treatment of hyperkalemia:
.calcium gluconate ( 1cc/kg IV ) over 3-5 min
•sodium bicarbonate (1-2 mEq/kg) over 5-10 min
• insulin + hypertonic dextrose: 0.1 U/kg with 1 cc/kg 50%
glucose over 1 hour
• sodium polystyrene (Kayexalate): 1 gm/kg . Can be repeated qh.
(Hypernatremia and hypertension are potential complications)
• dialysis
nutrition
•
•
•
•
provide adequate caloric intake
limit protein intake to control increases in BUN
minimize potassium and phosphorus intake
limit fluid intake
If adequate caloric intake can not be achieved
due to fluid limitations, some form of dialysis
should be considered
Management
• Anemia Hb<7
• Acidosis PH<7.15
• Neurologic
• Hypertension
HCO3<8
Indication for dialysis
• Volume overload
• Refractory electrolyte imbalance &
acidosis
• BUN> 100-150 or lower if rapidly rising
• Pericarditis
• Uremic encephalopathy