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Pedi gu review fluids and electrolytes
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Pedi gu review fluids and electrolytes

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    Pedi gu review fluids and electrolytes Pedi gu review fluids and electrolytes Presentation Transcript

    • Fluids and Electrolytes Pediatric GU Review UCSD Pediatric Urology George Chiang MD Sara Marietti MD Outlined from The Kelalis-King-Belman Textbook of Clinical Pediatric Urology 2007 (not for reproduction, distribution, or sale without consent)
    • Renal Function
      • Kidneys function to excrete water, solutes and metabolic waste
      • Regulate salt and water excretion
      • 99% of filtered water, sodium, chloride and bicarb is reabsorbed and returned to the plasma
    • Renal Function
      • Each nephron receives the ultrafiltrate of plasma, which passes through Bowman’s space and into the renal tubule
      • GFR=rate of ultrafiltrate formation
      • Term infant GFR is very low – 21ml/mn
      • Increases to 60ml/mn by 2 weeks
      • Adult level (120ml/mn) by 18-24 mo
    • Renal Function
      • Concentrating capacity of full-term and pre-term infant is diminished
      • Immature collecting tubules don’t respond to ADH
      • Infant can only increase urine osmolality to 600mOsm/kg vs 1200 in the adult
      • Newborn excretes dilute urine
    • Body Composition
      • Term newborn – total body water accounts for 70-75% of body weight
      • Decreases to 65% in infants/children
      • Decreases to 60% in adult male
      • Decreases to 55% in adult female
    • Body Composition
      • Body water is in constant state of osmotic equilibrium between intra/extracellular space
      • Fetus/newborn have more extracellular than intracellular fluid
      • With newborn diuresis and cellular growth, this changes
    • Body Composition
      • 2/3 TBW intracellular, 1/3 TBW extra by age 1 year (adult composition)
      • Extracellular space made up of plasma, interstitial fluid, pleural, peritoneal, synovial
    • Body Composition
      • Intravascular volume of premature or critically ill infant – 100ml/kg
      • Nl newborn – 80-90ml/kg
      • 1-6 y.o. – 75-80ml/kg
      • >6 y.o. – 65-70ml/kg
    • Body Composition
      • Plasma osmolality is maintained between 285-295 mOsm/kg
      • With extracellular loss (bleeding/dehydration), Increase ADH(from increased osmolality), Increase water
    • ADH
      • Bleeding/dehydration – osmoreceptors in hypothalamus sense increase-> release ADH-->bind to V2 receptors in collecting ducts->insertion of aquaporin 2 water channels->increase water permeabilty, concentrated urine
      • Osmoreceptors are very sensitive – respond to 1% change in osmolality
      • Other osmoreceptors stimulate thirst centers as well
    • Hypovolemia
      • MC – diarrhea
      • s/s – weight loss, tachycardia, low BP, dry mucous membranes, no tears, sunken fontanelle, decreased skin turgor
      • Mild dehydration (5% body weight loss) – if no clinical findings do not need blood work
      • Can usually attempt oral hydration
    • Hypovolemia
      • More severe (>5% body weight loss) – such as operative loss, goal is rapid extracellular fluid expansion to prevent shock and decreased renal perfusion
      • Bolus with NS or LR
      • Monitor weight, UOP and check frequent lytes
    • Sodium
      • Sodium is excreted in stool and sweat
      • Primarily excreted in kidneys and is main regulator of sodium balance
      • However, kids with CF have high sodium loss in their sweat
    • Sodium Abnormalities
      • Hyponatremia – hypervolemic, isovolemic, hypovolemic
      • Hypernatremia
    • Hyponatremia
      • Signs/Symptoms – nausea, anorexia, vomiting, muscle ache, headache, weakness, irritability, confusion, seizure, coma
      • Low sodium decreases the extracellular osmolality, thus water moves out of extracellular space and into the cells and causes cellular swelling, brain swelling can cause herniation
    • Correction
      • Need to correct the hyponatremia slowly to avoid CPM
      • CPM – when corrected too quickly, water will shift out of the brain too quickly and cause demyelination of the pons
      • No faster than 10-20 mEq/day
    • Hypervolemic Hyponatremia
      • CHF, liver disease, renal failure
      • Peripheral and pulmonary edema
      • Increase in TBW and Na, but more water
      • Decrease in blood volume secondary to third spacing or cardiac problem, so ADH increases water and aldosterone increases Na
      • If from renal failure, have expanded blood volume but kidneys fail to produce urine and get rid of the extra water
    • Hypervolemic Hyponatremia
      • Cardiac/liver – water/Na restriction, maybe diuretic
      • If renal failure – may need dialysis
    • Isovolemic Hyponatremia
      • SIADH – excess in water absorption
      • From CNS disorder, tumor, stress medications(narcotics, anesthesia), or extremely dilute feedings
      • Diagnosis of exclusion
      • ADH causes excess water and intravascular volume, thus kidneys lose Na to try to correct for this
    • SIADH
      • Urine osmolality > 100
      • Serum osmolality < 280
      • Serum Na < 135
      • Urine Na > 25
    • Treatment
      • If asymptomatic – water restriction
      • If symptomatic – 3% saline infusion, lasix infusion
    • Hypovolemic Hyponatremia
      • GI bug (diarrhea more than emesis), fasting, third space losses from burns, surgery, Na wasting nephropathy
      • Treat dehydration with isotonic saline (NS or LR)
    • Hypernatremia
      • Confusion, lethargy, weak, irritable, convulsions
      • Usually dehydrated with more water than Na loss
      • Improperly mixed formula, saltwater ingestion, hyperaldosteronism, nephrogenic/central DI, GI losses (ngt, emesis), post-obstructive diuresis
    • Hypernatremia
      • Because intravascular osmolality is high, water from cells moves out of the cell
      • In the brain, cells shrink and can cause decrease in brain volume and tearing of vessels ->intracranial bleeding (seizure/coma)
    • Hypernatremia by Cause
      • DI – only causes hypernatremia if pt does not have access to water or cannot drink it, newborn, neurologic impairment, emesis
      • Newborn – imbalance between loss and intake, usually lose water but may be increased if placed under the warmer, phototherapy for hyperbilirubineamia, or inadequate breast-feeding
      • Osmotic – mannitol or glucose (from diabetes) will cause pt to lose Na and water, but more water
    • Hypernatremia by Cause
      • Post-obstructive diuresis – increase in solutes causes loss of water, may have tubular damage may exacerbate water losses
      • Diarrhea – lose sodium and water, but more water, if child can drink they can replace the loss, at risk if also have emesis, anorexia or no access to water
    • Treatment
      • Most kids present dehydrated
      • Hydrate with NS bolus 10-20ml/kg
      • Frequent monitoring of Na level, do not want to correct too quickly (<12mEq/24 hr)
      • If correct too quickly and begin to have seizures, stop the hypotonic fluid and give 3% saline to increase Na and stop brain swelling
    • Potassium
      • Major intracellular cation
      • Low concentrations in extracellular fluid
      • Gradient between intracellular and extracellular allows muscle, cardiac and neuronal tissue to function
    • Hypokalemia
      • Arrhythmias, neuromuscular excitability, hyporeflexia, decreased peristalsis,
      • Usually due to GI (vomiting, ngt), gastroenteritis is MC cause in children
      • Treat with IV KCL if symptomatic (0.5-1 mEq/kg)
    • Hyperkalemia
      • Arrhythmias, muscle weakness, paralysis
      • Peaked T waves can turn to v.fib
      • Can be from hemolysis or drawing off a vein above K containing line, so re-chk
      • Causes – acidosis, rhabdo, tumor lysis, renal failure, CAH (21-hydroxylase deficiency), NSAID, diuretics
    • Treatment
      • K>6-6.5, chk EKG
      • If changes may need immediate cardiac stabilization with Calcium gluconate IV
      • Glucose with IV insulin drives K intracellularly
      • Bicarb drives K intracellularly
      • Exchange resins such as kayexalate po/pr will remove K from the body
      • If not in renal failure, a loop diuretic will also remove some K
      • HD
    • Hypocalcemia
      • Ca is mostly in bone matrix, only 0.1% is in ECF
      • Peri-op may be from low Mg, ARF, shock or rhabdo
      • S/S – Chvostek’s – facial nerve ->mouth twitch, Trousseau’s – finger twitch with BP cuff inflated
      • Only supplement if symptomatic
    • Hypomagnesemia
      • Dietary deficiency, chronic diuretic use
      • Can cause low Ca and make hypokalemia persist by causing renal K wasting
      • Should replace especially if have hypocalcemia and hypokalemia
    • Acid-Base Disturbance
      • Nl pH: 7.35-7.45
      • Need normal renal and pulmonary function to maintain this
      • If need to evaluate need AMA-renal and ABG
    • Metabolic Acidosis
      • Leads to: arrhythmia, hypotension and pulmonary edema
      • From addition of acid or removal of base from the plasma
      • Lungs compensate by increasing respiratory rate
      • Acids are buffered mostly by HCO3- but also other anions which make up the anion gap
    • Anion Gap
      • Na- (Cl + HCO3)
      • Normal range is 10-12 mEq/L
    • Non-Anion Gap Acidosis
      • Anion Gap within normal range
      • HCO3 is lost from kidneys/GI system, but Cl is absorbed to replace it
      • Hyperchloremic, non-anion gap, metabolic acidosis
      • Diarrhea can cause this
      • If acidosis mild-moderate (pH>7.2) – only require fluid and lyte replacement
    • Non-Anion Gap Acidosis
      • Once renal perfusion is restored, H+ can be excreted to correct the metabolic deficit
      • If severe (pH<7.2) – may also need IV bicarb
      • Chk K prior to bicarb because it can worsen hypokalemia
    • Anion Gap Acidosis
      • Lactic acidosis, diabetic ketoacidosis, poisons, renal failure
      • Lactic acidosis – sepsis, hypovolemia, treat according to the cause
      • Poison with salicylats or ethylene glycol – treat by removing the poison, gastric lavage, charcoal, occasionally HD
    • Metabolic Alkalosis
      • Symptoms – CNS changes, muscle irritability, cardiac arrhythmias, seizures
      • Lethargy and confusion from decrease in RR as body tries to hold onto C02
      • From losing acid or gaining base
      • Alkali ingestion, vomiting, ngt losses, hyperaldosteronism
    • Metabolic Alkalosis
      • If from vomiting – will need to give Cl, to allow renal excretion of bicarb, and K which is lost with vomiting
      • If due to hyperaldosteronism – spironolactone is an antagonist
    • Respiratory Acidosis
      • Increase in PCO2 from decreased RR
      • Airway obstruction, CNS depression, immaturity, neuromuscular problems
      • Treat by targeting the underlying problem
    • Respiratory Alkalosis
      • Decreaesed PCO2 from increased RR
      • Hyperventilation
      • Dizziness and confusion result from decreased cerebral blood flow
      • Treat the underlying problem
    • Maintenance Fluid
      • Weight based
      • 100ml/kg/day for kg 1-10
      • 50ml/kg/day for kg 11-20
      • 20ml/kg/day for kg >21
      • Hourly rate is 4:2:1 rule
      • UOP should be kept 1-2ml/kg/hr
    • Nutrition
      • Hypoalbuminemia has been correlated with increased mobidity/mortality
      • Protein needs of neonates and infants >>children and adults
      • Infant maintenance:75-100 kcal/kg/day
      • Infant growth:100-120 kcal/kg/day
      • Measurement
        • Albumin (20 days)
        • Transferrin (8.8 days)
        • Prealbumin (2 days)
        • RBP (Retinol binding protein)-12 hrs excreted in urine
    • Enteral Alimentation
      • Preserve normal intestinal villus to prevent bacterial translocation
      • Commercial preparations 35-45 kcal/kg/day
      • Infusion rates start at 10 cc/hr to maximum 60 cc/hr
      • Minimal infusion of 20 cc/hr needed for gut preservation and immune stimulation
      • Malnutrition can exacerbate malabsorption and more aggressive approach may be warranted
    • Isotonic Parenteral
      • PPN
      • Solution is < 600 mOsm
      • Depends on mobilization of endogenous fat stores for fuel and provision of amino acids for protein needs
      • Minimizes catabolism but does not provide for anabolism
    • Hypertonic
      • Rebuild mass and achieve anabolism
      • Prolonged starvation
        • Term 4-5 days/pre-term 1-2 days
      • GI dysfunction, chronic malabsorption, diarrhea, bowel obstruction, EC fistulas
      • 20-25% dextrose, 4.25% a.a.; essential fatty acids, glutamines (mucosal preservation)
      • Complications: Technical, Septic (2-3%), Metabolic
        • (HONK-->cerebral dehydration with coma/death)-->add insulin; elevation of LFTs from excess calories with increased insulin response and hepatic lipogenesis; electrolyte abnormalities