Pedi gu review fluids and electrolytes


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Pedi gu review fluids and electrolytes

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