Acute Kidney Injury - ACH Pediatric Residents

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

Classification - pRIFLE U/O

Risk

eCCl dec 25%

Injury

eCCl dec 50%

Failure

eCCl dec 75%/ infarct -toxins/severe HUS

Hemolytic Uremic Syndrome 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 Tubular Necrosis 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 

 

AIN

Proximal: aminoglycosides, amphotericin B, cisplatin, immunoglobulins, contrast Distal: NSAIDs, ACEi, lithium, cyclophosphamide Obstruction: sulfa, acylovir, methotrexate

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… Everyone gets a urinalysis…

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 (postinfxn) -hematuria = AIN, vasculitis, infarction, obstruction

And even more information from urine… Urine osmolality: 



Typically low in ATN (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 ?? >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, creatinine Creatinine is usually elevated 

 

Normal Cr varies by age Age

Normal range (umol/L)

Newborn

27-88

Infant

18-35

Child

27-62

Adolescent

44-88

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”

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: pRIFLE met -estimated CrCl -oliguria NORMAL urinalysis

ABNORMAL urinalysis

Ultrasound

PRE-RENAL

Low ECF volume -GI loss -diuresis -hemorrhage

RENAL POST-RENAL

Low vol to kidney -bilateral ureteric obstruction -heart failure -single kidney + ureter obs -m eds (NSAIDs, ACEi, ARB) -bladder/urethra obs -vascular disease

Vascular disorders

Artery -RAS -Takayasu, PAN, KD -can think of drugs here too

Veins -thrombosis

Parenchymal disorders

Glomerular disorders

Tubular disorders

AIN -drugs -infection -autoimmune

ATN -ischemia -contrast

plugged -crystals -globins -drugs

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 Hypovolemia Goal: maintain renal perfusion

Euvolemia

Hypervolemia Type Title Here

Crystalloids (NS) -bolus, rpt -no change? Consider invasive monitors

Monitor ins/outs -daily weights -ins=outs + insensibles

Fluid removal/restriction -furosemide (2-5mg/kg) -no change? Consider RRT

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 balance Electrolytes - esp K, PO4, Ca Acidosis Nutrition Dialysis - talk later today

References Akcan-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-anddiagnosis-of-acute-kidney-injury-acute-renal-failure-inchildren?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-acutekidney-injury-acute-renal-failure-inchildren?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.