Scott Wenderfer, MD/PhD

Sept, 2004

Acute Kidney Failure

Case Presentation

• 7 yo previously healthy girl • 3d general malaise, swelling, worsening dyspnea• recovering from URI• 2d cola colored urine & more recent ↓ in UOP• NO dysuria, flank pains, HA, or fevers• +chest pains, +blurred vision

Case Presentation

• In the ER, BP 152/79, in mild respiratory distress• bilateral crackles ↓ breath sounds• pitting edema to the mid thighs • dark colored urine• CXR reveals bilateral infiltrates

139 106 73

6.9 13 5.3

ABG = 7.24 / 25 / 75

11.8

36.222.5 14.6

UA: 4+ prot, 4+ blood, + RBC casts

AG 20AG 20

Acute Kidney Failure

• Difficult to define:– There is no “normal” serum Creatinine– Creatinine is a poor marker for true GFR

• Not much literature regarding Pediatrics

• Usually defined in adults as:– A doubling of the serum creatinine– A rise in creatinine of 0.5mg/dL/day

Acute Kidney Failure

• Functional Definition– An acute deterioration in kidney function

manifested by fluid and electrolyte abnormalities

– Difficult to define how much abnormality is required for term to be accepted

Acute Kidney Failure

• Nephrology is often called too late:– Remember that for each doubling of creatinine,

kidney function has been cut in half• When a child’s Scr goes from 0.30.6, half of the

kidney function is already gone

• When it gets to 1.2, the kidney is working only 25%

– We often aren’t called until the creatinine is 2-3• By then, patients are already well into kidney failure

Acute Kidney Failure

• Another way to think about it:– The early changes in Scr correspond to much

more renal dysfuction than when Scr is already high

• 0.51.0 means GFR has gone from 100ml/min to 50 ml/min ( a drop of 50 ml/min)

• 4.06.0 is only a change from 12.5 to ~9ml/min

Acute Kidney Failure

Causes of Prerenal Acute Kidney Failure (↓ kidney blood flow)

• Decreased effective extracellular volume– True volume loss

• Vomiting, diarrhea, hemorrhage, burns, diuretics

– Redistribution• hepatopathy, nephrotic syndrome, pancreatitis, peritonitis

– Decreased cardiac output• cardiogenic shock

– Peripheral vasodilation• hypotension, shock, renal vasoconstriction or inflammation

Causes of Parenchymatous Acute Kidney Failure

• Acute Tubular Necrosis– Hemodynamic

• CV or other surgery, sepsis, severe dehydration

– Toxic• antimicrobials, immunosuppressive, venoms, mannitol

– Intratubular deposists• uric acid, myeloma

– Organic pigments• Myoglobin (rhabdomyolisis), hemoglobinuria

Acute Tubular Necrosis

• Acute Tubulointerstitial Nephritis• Acute Glomerulonephritis

– Postinfectious: streptococcal or other

– HSP

– Systemic lupus erythematosus

– Etc.

• Vascular Occlusion– Renal artery thrombosis, bilateral renal vein thrombosis

Parenchymal Acute Kidney Failure

Most Frequent Causes of ATN

• Antimicrobials– Penicillin– Ampicillin

• Analgesics– Fenoprofen/Ibuprofen– Naproxen

• Other drugs– Cimetidine– Allopurinol

• Immunological• Infections

• Neoplasia• Idiopathic

– Associated with uveitis and adolescent females

Acute Kidney Failure

• Post-Kidney Obstruction• BPH (older men)

• Stones

• UPJ, UVJ obstruction

• Posterior Urethral Valves (boys)

• Trauma

• Compression by tumor, hemorrhage

Urinalysis in Acute Renal Failure

Urinalysis in ARF

FENa: You are what you eat

• We are in general at steady state

• Daily American Diet has ~ 4 grams Na

• Thus, to maintain homeostasis, we excrete roughly 4 grams Na/day

• Question is how much Na do we filter?

FENa: Let you tubules do the rest

• ~25% of Cardiac output goes to kidneys– 500ml/min in an adult

• ~20% of the plasma is filtered– 100ml/min, or 144 liters/day

• Since plasma is what gets filtered – 144liters * 140mEq/L = ~20,000 mEq, or 450 grams Na

• Tubules reabsorb roughly 99%– 142 Liters of H20 and 446 grams of Na– So FENa should be ~1% if tubules are working

Fractional Excretion of Sodium

Urine Na / Plasma Na

Urine Cr / Plasma Cr

U *V /P

Evaluating a FENa

• If Kidney tubules think you are Volume low– They will reabsorb more H20 and Na+

– FENa is <1% in prerenal diseases

• If tubules are broken (ie intrinsic renal dz)– They are unable to absorb as much– FENa is >3% in intrinsic kidney diseases

Acute Kidney Failure

• Considerations– Blood pressure status– Potassium status– Volume status– Acid Base status

Complications: Hypertension

– Hypertensive Emergency• Elevated blood pressure with evidence of end organ

damage– Kidney failure

– Heart failure (pulmonary edema)

– Stroke

– Seizure

– Hypertensive Crisis • Markedly elevated blood pressure without evidence

of end organ failure

Hypertensive Emergencies

• Symptoms– Headache– Mental status change– Blurry vision– Seizures– Respiratory failure– Chest pain

Antihypertensive Drug Doses

Drug Dose

Nicardipine 1-10 μg/kg/min IV drip

Labetolol 0.2-0.4 mg/kg IV push

Labetolol 0.25-1 mg/kg/min IV drip

Nitroglycerin 0.05-0.1 μg/kg/min IV

Nitroglycerin SL 0.4 mg Sublingual

Nitroprusside 0.3-8 μg/kg/min IV drip

Diazoxide 1-3 mg/kg/ IV push

Nifedipine SL 0.25-2 mg/kg/dose sublingual

Hydralizine 0.2-0.5 mg/kg/dose IV

Complications: Hyperkalemia

• Mechanism: ↑ potassium release from cells

• Differential Diagnosis • Metabolic acidosis (DKA, sepsis)

• Insulin deficiency

• Tissue catabolism

• Exercise

• Tissue Destruction (crush injury, electrical burns)

• Digitalis overdose

Hyperkalemia

• Mechanism: Decreased Excretion• Kidney Failure

• Hypoaldosteronism

• Hypovolemia

• Selective Impairment of excretion

Hyperkalemia EKG Findings

• In order of occurrence– Peaked T waves– Reduced P wave voltage– Widening of the QRS complex– Sinusoidal EKG pattern– Ventricular Fibrillation

EKG Findings in Hyperkalemia

EKG Findings in Hyperkalemia

Treatment for Hyperkalemia

• DIALYSIS IS NOT THE INITIAL TREATMENT OF

CHOICE

Pharmacologic Treatment

Drug Dose

Calcium Gluconate 0.5-1 mg/kg IV

Insulin and Glucose Glucose 0.5 g/kg Insulin 0.1unit/kg

Beta Agonists 10 mg nebulized/hour

Sodium Bicarbonate 1-2mEq/kg IV

Kayexalate 1 gm/kg PR for 1 hour, then repeat

Complications: Pulmonary Edema

• Definition

– Accumulation of fluid in the alveolar space either due to hydrostatic forces or capillary leak

• Can occur with or without volume overload

• S/Sx: CP, SOB, tachypnea, wheezing, pink frothy sputum

• Tx: O2, position sitting up, warm blanket, anxiolytics, CPAP/BiPAP, intubation w/ PEEP

Treatment of Pulm Edema

Drug Dose

Lasix 0.5-2 mg/kg/dose IV

Nitroglycerin SL, paste, or 1-10 μg/kg/min IV drip

Dobutamine 2.5-20 μg/kg/min IV drip

Morphine 0.2-0.4 mg/kg/dose IV

Complications: Metabolic Acidosis

• Definition– Disturbance in the acid base homeostasis

– Causing a decrease serum bicarbonate concentration• by the addition of exogenous acid to the serum

- or -

• the loss of endogenous bicarbonate

• Anion Gap– Na+ - (Cl- + HCO3

-) = AG

– Normal is ~10

Metabolic Acidosis

• Differential Diagnosis– High anion Gap acidosis (MUDPILES)

• Methanol Inborn errors of metabolism

• Uremia (Kidney Failure) Lactic Acidosis

• Diabetic Ketoacidosis EtOH, Ethylene Glycol

• Paraldehyde Salicylates

– Normal anion gap• Diarrheal losses

• Renal tubular acidosis

Metabolic Acidosis Treatment

• In AKF, kidney is unable to excrete titrated acids, leading to an increased number of circulating, unmeasured anions

• Thus you get a high gap acidosis– Resolves as kidney function improves– In severe cases may need to treat with Bicarb

Indications for Dialysis

• Severe pulmonary edema• Hyperkalemia• Severe electrolyte abnormalities• Severe metabolic acidosis• Specific intoxications• Specific inborn errors of metabolism

• …which is unresponsive to medical therapy

Definitions- Solute Removal

• Dialysis- OsmosisPermeableMembrane Solute Equilibrium

Dialysis

Blood Dialysate Blood NewDialysate

Blood Dialysate

DialysateFlow

Definitions- Solute Removal

Definitions- Fluid Removal

• Ultrafiltration

Water

Amount ofUltrafiltration

WaterWater

Suction

• Convection

Blood Dialysate Blood Dialysate

Blood Dialysate

Suction

Equilibrium WithoutSuction

Definitions- Solute Removal

Definitions- Fluid Replacement

• Hemofiltration

ReplacementFluid Given

SuctionApplied

Equilibrium Convection Hemofiltration

Blood Dialysate

DilutedBlood

Requirements for CRRT

• Adequate vascular access

• CRRT machine

• Dialysate

• Anticoagulation– ACT machine

• Replacement fluid

• Specialized nursing care

Definitions- Dialysate

• Peritoneal dialysate can be used• Or the following can be made in house

– NaCl 140 mEq/L– KCl 3 mEq/L– Dextrose 100 mg/dl– MgSO4 1.5 mEq/L– Lactate 35 mEq/L– CaCl 3.5 mEq/L

• All values can be adjusted to conform to the individual patient

Alphabet Soup

• CVVHF• Continuos Veno-Venous Hemofiltration

• CVVHD• Continuous Veno-Venous HemoDialysis

• CVVHDF• Continuous Veno-Venous HemoDiafiltration

CVVHD Circuit

CVVHF Circuit

CVVHDF Circuit

H2OH2O

H2O

Anticoagulation

• Saline flushes every hour

• Heparin– Keep ACT 190-210

• Citrate– Need calcium chloride drip

– Need low sodium dialysate

– Occasionally need hydrochloric acid drip

CRRT in Pediatrics

• Uncommon procedure with very little literature

• Complication rate is low – 10-15% in most series– Bleeding is the most common complication

• No controlled studies have been performed

Pediatrics CRRT Issues

• Vascular Access is the main problem– Pediatric blood vessels are small– Small, long catheters have high resistance– Catheters problems (flow, clot) are the

most common cause of circuit failure

CRRT Conclusions

• Confusing nomenclature

• Many modalities available and each has theoretical advantages and disadvantages

• Anticoagulation in pediatrics is likely not necessary

Mortality Trends and Acute Renal Failure

Duration and Resolution of ARF

• Mean 14 days to recovery• 78% of pts with ARF died

within 2 wks of renal injury• In the 60% who survived renal

function recovered completely• If > 1 month, 90% had final

resolution of ARF one way or the other

• In patients who never recovered; severe GN/ Vasculitis/Systemic disease

Final Thoughts on Case

• classic story of acute post infectious glomerulonephritis with subsequent acute kidney failure. While most of these children do quite well, a rocky course, including ICU admission and dialysis is not uncommon

Plug for Nephrologists

• Early nephrology consultation has been proven, at least in adults, to improve mortality and morbidity in ICU patients.