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ACUTE RENAL FAILURE
Academic Half Day
February 9, 2012
Objectives
To review: the etiologies of acute kidney injury (AKI) in the pediatric population the work-up/diagnosis of AKI the management of AKI What is AKIs?
“abrupt reduction in kidney function as measured by a rapid decline in GFR”
Previously known as Acute Renal Failure
Now failure represents one end of the spectrum
Etiology is variable
Definitions/classifications have varied in the literature…
Classification - pRIFLE
Risk
Injury
Failure
Loss
End-stage
U/O <0.5cc/kg/h x 8h
Failure > 3 months
Persistent failure >4wks
eCCl dec 50%U/O
<0.5cc/kg/h x 16h
<0.3cc/kg/h x 24h/Anuric x 12h
eCCl dec 75%/ < 35ml/min/1.73m2
eCCl dec 25%
Leads to: Impaired excretion of nitrogenous waste Impaired water and electrolyte balancing Impaired acid/base regulation Impaired vascular tone regulation
Burden of disease
Incidence (US): 0.8/100 000; ~1/10 in ICU Increasing
Independent risk factor for ICU mortality
Increases length of hospital stay
May lead to chronic renal failure (40-50% ICU)
Etiologies: a general approach
Though likely multifactorial, can be divided into:
Pre-renal Renal Post-renal
Pre-renal causes:Any cause which results from kidney seeing to little blood flow
Volume deplete: GI
Vomiting Diarrhea
Bleeding Trauma Surgery
Diuresis Diabetes - DM, DI Drugs
Kidney sees less volume: Sepsis CHF Cirrhosis Vascular - also consider in renal
RAS Thrombus Takayasu, PAN, KD
Drugs NSAIDs ACEi ARBs
Renal causes
Vascular:Microvasculature: Sickle cell disease HUS Tumour lysis rhabdomyolysis
?Syndromes Hepatorenal Cardiorenal Pulmonary-renal
Glomerular:Glomerulonephritis:•Post-infectious•membranoproliferative•SLE•HSP
Tubulo/Interstitial:Acute tubular necrosis -secondary to nephrotoxic insults or poor perfusion
Acute interstitial nephritis -drugs -infxn
Cortical dysplasia
-hypoxia/ischemia->infarct -toxins/severe HUS
?Sepsis inflamm, not all volume related
Hemolytic UremicSyndrome
History of Ecoli, Shigella, shiga-toxin…
Atypical (non-diarrhea, non-shiga-toxin)
Hemolytic anemia with fragmented RBCs
Thrombocytopenia
Renal injury
CNS, liver, pancreas can also be affected
Post-infectious glomerulonephritis
Occurs in ages 5-12, post-GAS.
Presentation can be asymptomatic to nephritis complete with gross hematuria, proteinuria, HTN, edema
Labs: abnormal urinalysis, low complement
Rx: supportive.
Prognosis: most make complete recovery.
HSP
-Causes renal issues d/t IgA deposition.
-A/W palpable purpura, arthritis, abdo pain.
-Renal more likely to be an issue in older kids
-Rx: if crescenteric, GN - steroids.
-prognosis: often relapses. Can have late deterioration even if full recovery. 10-30% adults go on to have end-stage disease.
Acute TubularNecrosis
Describes an end effect of tubular damage… Secondary to perfusion insults Secondary to toxins
Change in blood flow, obstruction and passive filtrate backflow into tubular cells can cause a cycle leading to further death…
AIN
Drugs (71%) - 1/3 antibiotics Penicillins, cephalosporins, NSAIDs, sulfonamides, cipro,
rifampin, PPIs, allopurinol… and more
Infection (15%) Strep, Legionella, leptospirosis, CMV, EBV… many
Tubulointersitial nephritis and uveitis (5%)
Autoimmune: SLE, Sjogren’s
Sarcoidosis
Idiopathic (8%)
Nephrotoxins
Vascular effect ACEi, cyclosporine, tacrolimus
Tubular effect Proximal: aminoglycosides, amphotericin B,
cisplatin, immunoglobulins, contrast Distal: NSAIDs, ACEi, lithium, cyclophosphamide Obstruction: sulfa, acylovir, methotrexate
AIN
Post-renal causes
Two kidneys - distal or bilateral proximal obstruction
Single kidney - obstruction anywhere Posterior urethral valves Ureteropelvic junction obstruction Ureterovesicular junction obstruction Ureterocele Stones Tumour Hemorrhagic cystitis Neurogenic bladder
On history…
? pre-renal: Vomiting, diarrhea, bleeding, sepsis, dec PO Drug use - inc NSAIDs
? renal: Bloody diarrhea? (HUS) Recent illness? (PSGN) Crush
injury? Drug use: aminoglycosides, antifungals, chemo Associated lung/heart/liver symptoms? (dual organ)
? post-renal:
On physical…
Pre-renal: Dehydration Signs of heart failure/cirrhosis/sepsis
Renal: Edema (nephrotic syndrome) Purpura (HSP
Post-renal: palpable bladder?
What to order?
BUN, Cr, lytes, fractional excretion of sodium
Urinalysis
On labs…
NORMAL:
-pre-renal (may be concentrated)
-post-renal
-ATN
ABNORMAL:-brown granular/epithelial casts = ATN-red cell casts = glomerulonephritis-proteinuria = glomerular-pyuria, white cell casts = UTI or glomerulonephritis (post-infxn)-hematuria = AIN, vasculitis, infarction, obstruction
Everyone gets a urinalysis…
And even more information from urine…
Urine osmolality: Typically low in ATN (<350 mosmol/kg) Typically high in pre-renal disease (>500)
Urine volume: Often low, especially given criteria for AKI. However, some ATN is non-oliguric
Urine eosinophils
Urine sodium…
Sodium excretion
Why? Helps distinguish pre-renal vs ATN… >30-40 mEq/L = ATN <10 mEq/L = effective volume depletion
(20-30 in infants) BUT what if there is a large urine output?
Fractional Excretion of Sodium
FENa compensates for the urine output…
UNa x PCr
PNa x UCr
…can also be thought of as
UNa/PNa
UCr/PCr
<1% --> pre-renal disease
1-2% --> ??
>2% --> ATN
Bloodwork…
CBC: look for MAHA, thrombocytopenia
Extended lytes. Renal injury can result in: Hyperkalemia Hyperphosphatemia Hypocalcemia Metabolic acidosis
Other options, depending on history: ANCA,
ANA, ASOT, complement, drug levels…
And of course, creatinineCreatinine is usually elevated
Normal Cr varies by age
Note Cr can NOT be used to estimate GFR in acute kidney injury…
This is why the search is on for a “troponin of the kidneys”
Age Normal range (umol/L)
Newborn 27-88
Infant 18-35
Child 27-62
Adolescent 44-88
Troponin of the kidneys?
Unfortunately, not yet… Some ideas: Urinary neutrophil gelatinase-associated lipocalin
(NGAL) Increased 50-fold, and 24h before serum Cr Has been shown to predict AKI severity in SLE, HUS, renal
transplant patients
Kidney injury molecule - 1 (KIM-1) IL-18
Imaging
Ultrasound - in all children if etiology unclear # of kidneys Size of kidneys Obvious parenchymal damage Obstruction Thrombus/vessel occlusion
Renal biopsy
Only when diagnosis remains unknown, or
there is a failure to respond to treatment
Approach summary:
Ultrasound
Low ECF volume-GI loss-diuresis
-hemorrhage
Low vol to kidney-heart failure
-meds (NSAIDs, ACEi, ARB)-vascular disease
PRE-RENAL
-bilateral ureteric obstruction-single kidney + ureter obs
-bladder/urethra obs
POST-RENAL
NORMALurinalysis
Artery-RAS
-Takayasu, PAN, KD-can think of drugs here too
Veins-thrombosis
Vascular disorders
Glomerular disorders
AIN-drugs
-infection-autoimmune
ATN-ischemia-contrast
plugged-crystals-globins-drugs
Tubular disorders
Parenchymal disorders
RENAL
ABNORMALurinalysis
pRIFLE met-estimated CrCl
-oliguria
Treatment
Principles:
1. FEN
2. Avoid complications
3. Treat underlying cause
Generally pediatric nephrology will be involved.
FEN - fluids
Child can be hypo-, eu- or hypervolemic.
FLUID STATUS
Crystalloids (NS)-bolus, rpt
-no change?Consider invasive monitors
HypovolemiaGoal:
maintain renal perfusion
Monitor ins/outs-daily weights
-ins=outs + insensibles
Euvolemia
Fluid removal/restriction-furosemide (2-5mg/kg)
-no change?Consider RRT
HypervolemiaType Title Here
HTN can occur and is usually secondary to volume overload.Treatment based on diuretic response, severity.
FEN - electrolytes
Hyperkalemia - if severe (>7) - C BIG K Die… Don’t give K (IVs, low K diet) stabilize the cardiac membrane - IV calcium
gluconate Move K ECF -> ICF by:
Insulin (with glucose) Sodium bicarb Beta agonists
Remove K from the body - kayexalate Can try diuretics - unlikely to do enough RRT if the above doesn’t work
FEN - electrolytes
Acidosis Respiratory compensation can be enough Sodium bicarb ONLY if life-threatening and/or
contributing to hyperkalemia Def not if pH >7.2 or bicarb >14mEq/L Can decrease Ca further -> seizures Can increase intravascular volume
If refractory volume overload, hypernatremia -> RRT
FEN - electrolytes
Hyperphosphatemia: Low phosphate diet Binders
Hypocalcemia: Calcium gluconate Can pre-empt if sodium bicarb being given
FEN - Nutrition
AKI is a catabolic state
Ensure adequate calories
- 120kcal/kg/d in infants
- usual maintenance for children
PO -> enteral -> TPN
If fluid balance off with adequate nutrition: RRT
Avoid complications
Including making things worse…so no:
Aminoglycosides
NSAIDs
Antifungals
Immunosuppressive drugs
Contrast media
Renal Replacement Therapy (RRT)
Indications:
1. Uremia s/s - pericarditis, neuropathy, decline
2. Azotemia - BUN >36
3. Refractory fluid overload - HTN, pulm edema, CHF
4. Refractory hyperK, hypo/hyperNa, acidosis
5. Nutritional support with fluid balance issues
RRT
Options:
Continuous renal replacement therapy
Peritoneal dialysis
Hemodialysis
Prognosis
Mortality: 60% (critically ill)
20-25% go on to have some degree of chronic renal issues
Take home points
Etiology: Best divided into pre-, renal and post-renal
Work-up: Urinalysis, ultrasound, bloodwork…
Treatment:Fluids - close balanceElectrolytes - esp K, PO4, CaAcidosisNutritionDialysis - talk later today
ReferencesAkcan-Arikan A, Zappitelli M, Loftis L, Washburn K, Jerrerson L, and Goldstein S. Modified RIFLE criteria in critically ill children with acute kidney injury. Kidney International; 2007: 71: 1028-35.
Basu R, Devarajan P, Wong H, and Wheeler S. An update and review of acute kidney injury in pediatrics. Pediatric Critical Care Medicine; 2011: 12(3): 339-47.
Imam A. Clinical presentation, evaluation, and diagnosis of acute kidney injury (acute renal failure) in children. Uptodate. Accessed Feb 8, 2012 at http://www.uptodate.com.ezproxy.lib.ucalgary.ca/contents/clinical-presentation-evaluation-and-diagnosis-of-acute-kidney-injury-acute-renal-failure-in-children?source=search_result&search=acute+kidney+injury&selectedTitle=2~150
Imam A. Prevention and management of acute kidney injury (acute renal failure) in children. Uptodate. Accessed Feb 8, 2012 at http://www.uptodate.com.ezproxy.lib.ucalgary.ca/contents/prevention-and-management-of-acute-kidney-injury-acute-renal-failure-in-children?source=search_result&search=acute+kidney+injury&selectedTitle=1~150
Kliegman R, Stanton B, Geme J, Schor N, and Behrman R. Nelson Textbook of Pediatrics 19th e.
Elsevier; 2011: 1814-22.