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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