acute renal failure (arf) acute kidney injury (aki) mitra basiratnia ped nephrologist sums
TRANSCRIPT
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
End-stage kidney disease
Persistant AKI = complete loss of renal function > 4 weeks
Increased creatinine × 3 or GFR decrease >75% or creatinine > 4 mg/dL
(acute rise >0.5 mg/dL)
UO < 0.3 ml/kg/hr × 24 hours or anuria × 12 hours
Increased creatinine × 2or GFR decrease > 50%
UO <0.5 ml/kg/hr × 16 hours
Increased creatinine × 1.5or GFR decrease > 25%
UO<0.5 ml/kg/hr × 8 hours
Bellomo et al. Crit Care 2004;8:R204-R212.
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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
Clinical Approach to AKI: Pre-, Intra-, and Post-Renal
HistoryVolume status
UltrasoundUrinalysis US shows
Hydronephrosis
Post-Renal
Urinalysis Normal
UrinalysisAbnormal
Tubulointerstial Disorders
Glomerular and Vascular Disorders
Pre-renal
Nephrologists Clinical Approach to AKIHistory
Volume StatusUltrasoundUrinalysis
Hydronephrosis
Post-Renal
Prostate disease BPH
CancerPelvic malignancy
StonesStricture
Retroperitoneal fibrosis
Normal Urinalysis
Pre-Renal
Low ECF Volume GI losses
Hemorrhage Diuretics
Osmotic diuresis
Altered renal blood flowor hemodynamics
Sepsis Heart failure
Cirrhosis/Hepatorenal syndrome Hypercalcemia
Medications NSAIDs/Cox-2 inhibitors
ACE inhibitors Angiotensin II receptor blockers
Vascular disease
Vascular Disorders
TubulointerstitialDisorders
Glomerular Disorders
Tubular obstruction Crystals
Calcium oxalate (Ethylene glycol,
orlistat) Indinivir Acyclovir
Methotrexate Tumor lysis syndrome
Myeloma cast nephropathy
Acute tubular necrosis Ischemic
Nephrotoxic Contrast-induced Rhabdomyolysis
Acute interstitial nephritis Medication-induced
Autoimmune Sjogren syndrome
Sarcoidosis Infection-related
Arterial Renal artery stenosis
Renal artery thromboembolism Fibromuscular dysplasia
Takayasu arteritisMedium vessel
Polyarteritis nodosa Kawasaki disease
Small vessel Glomerulonephritis
Thrombotic microangiopathies Cholesterol emboli
Renal vein Renal vein thrombosis
Abdominal compartment syndrome
Renal parenchymal disorders
Abnormal urinalysis
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
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] x 100 %
[urine creatinine/serum creatinine]
renal indices
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 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, rhabdomyolisisurine (+) blood but (-) red blood cells CPK K+
treatment aggressive hydration + urine alkalinizationmannitol / 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
potassiumOliguric renal failure is often complicated by hyperkalemia, increasing the risk in cardiac arrhythmiasK>6 resinK>7 emergency treatmentTreatment 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