September 2 nd, 2010. Acute Renal Failure Prerenal (Most Common) Results from hypoperfusion to...
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Transcript of September 2 nd, 2010. Acute Renal Failure Prerenal (Most Common) Results from hypoperfusion to...
September 2nd, 2010
Acute Renal FailurePrerenal (Most Common)
Results from hypoperfusion to kidney Dehydration, CHD, Sepsis
Decreased perfusion -> ischemic injury -> fall in GFRCompensation:
Relax afferent arterioles (decreasing renal vasc resistance) Increased catecholamines Increased vasopressin Renin-angiotensin system
Enhanced Na and water reabsorption to increase perfusion May secondarily worsen oliguria
Vasodilatory prostaglandins -> relax microvasculature
*Recognize the causes of acute renal failure in infants and children
Diagnosis: Prerenal ARFHistory should fitRenal imaging normal
Prerenal Renal Tubular Function
U Na+ <20 >40 Sodium Retention
U osm >500 <400 Urine Concentration
FE Na+ <1% >3% Na retention+urine concentration
BUN/Cr Ratio Increased
Intrinsic Renal DiseaseParenchymal injury (ischemic or toxic)
ATN, interstitial nephritis, HUS, glomerulonephritis, nephrotoxic drugs
May see RBC or granular casts
Intrinic Renal FailureRenal scans (Mg-3) may identify areas of
poor functionBx may be needed
Prerenal Renal Tubular Function
U Na+ <20 >40 Sodium Retention
U osm >500 <350 Urine Concentration
FE Na+ <1% >3% Na retention+urine concentration
BUN/Cr Ratio Increased
Postrenal FailureObstruction to urinary flow
Calculi, posterior urethral valves, UPJ obstruction
Renal damage results from increased pressure
Urinary sediment findings variableImaging
U/SRadioisotope scan
ARF: ManagementRenal perfusionBalancing fluid/ electrolytesControlling BPAnemiaAdequate nutritionRenal dosing of medsDialysis (when needed) *Plan the initial treatment for a child with acute renal failure *Recognize the complications of ARF
Renal PerfusionAdequate CVPMay require fluid administrationVasoactive agents
Low-dose dopamine can improve renal blood flow, but the actual benefit is debated in literature
Fluid ManagementIf unstable, bolus!If stable but ?volume depleted, gentle bolusOnce intravascular volume re-established,
minimal fluids
Know that coexisting volume depletion should be corrected in patients with acute renal failure
Fluid ManagementDiuretics (Furosemide, Mannitol)
Benefit: May help volume overload Decrease intratubular obstruction Remove K+ (furosemide)
Downfall: Do not prevent need for dialysis Could worsen renal perfusion and injury
Restore intravascular volume and measure urine lytes prior to diuretics
LytesHyponatremiaHyperkalemiaAcidosisHypocalcemia
AnemiaConsider transfusion:
Active bleedingHemodynamic instabilityHct < 25
HypertensionSecondary to volume overload, increased
vasc toneDiuresis or dialysis may be requiredIV antihypertensives if >99%ile
Labetalol, nicardipine, enalapril
NutritionPatients are in catabolic state, malnutrition is
commonFor infants, low phos formulaOlder kids, may need low phos, K+, Na+Balance nutrition with fluid restrictionTPN
Know the importance of nutrition in a child with ARF
MedsRenal dose and interval
Know that drug dosages must be modified in ARF
DialysisIndications
CHFAnemiaHyperkalemiaSevere acidosisPericarditisInadequate nutrition
CVVH most commonly used acutelyCan use with low BPs
Glomerular Disease
Determine the PatternNephrotic Pattern:
No inflammation on histologyNephrotic range proteinuriaInactive urine sediment (few cells or casts)
Nephritic Pattern:Inflammation by histologyUrine sediment: RBCs, WBCs, granular and
RBC casts, variable proteinuria
Indicators of Glomerular Bleeding
What about function?Reduction in GFR
Progression of diseaseSuperimposed insult
Decreased perfusion Possibly reversible
Schwartz formula May overestimate GFR
Schwartz FormulaGFR = k X Ht(cm) / Serum Creat
k = 0.33preterm infantsk = 0.45infantsk = 0.55children/ adolescent girlsk = 0.7 adolescent boys
Blood TestsTest Disease
Low C3 PSGN, MPGN-II,
Low C3, C4 Lupus, MPGN-I, shunt nephritis, SBE
ANCA Systemic vasculitis (Wegner’s)
IgA IgA nephropathy, HSP
Anti-GBM Goodpasture’s
ANA, antiDNA Lupus
*Differentiate acute post-strep GN from other forms
Renal BiopsyGoals
Confirm DxDetermine extent of injuryPredict outcome
TimingDependant on clinical setting
Rapidly Progressive (Crescentic) GNClinical Syndrome
Features of glomerular diseaseProgressive loss of renal function (days, weeks)May be presentation of many underlying dx
TxPulse methylprednisoloneCyclophosphamideConsideration of plasmapheresis (anti-GBM)
Membranoproliferative GNMost common chronic GN in older kids and
adultsMay present with nephrotic syn OR acute
nephritic syndromeRenal function normal to severely decreased50% progress to end stage renal disease in
10yrsNo proven therapy
Post-Streptococcal GlomerulonephritisAcute nephritic syndrome 1-2wks after strep
pharygitis, or up to 6wks after impetigoStrep Antibody titers positiveHematuria, edema, HTN, renal insufficiency.U/A: RBC casts, proteinuria, WBCLow C3Very similar presentation to MPGN, but
resolves by 2mos
•Acute onset•Hematuria, edema, HTN•Impaired renal function•U/A: RBC casts, proteinuria, WBC•Low C3•Lasts longer than 2 months•Confirmed on Biopsy
•Acute onset•Hematuria, edema, HTN•Impaired renal function•U/A: RBC casts, proteinuria, WBC•Low C3•Strep antibodies positive•Resolves by 2 months
Membranoproliferative GN Post-strep GN
Post-Streptococcal GlomerulonephritisTreatment:
Manage the acute effects of renal insufficiency, HTN
Amoxicillin Prevent spread of nephritogenic organisms Does not affect natural course of disease
*Plan the initial management of PSGN
Post-Streptococcal GlomerulonephritisPrognosis
Complete recovery 95% Renal function and C3 normalize by 6wks HTN up to 3mos Hematuria/proteinuria for prolonged periods
If chronic, think MPGN *Know sequence of resolution: C3, hematuria, proteinuria