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Fluids and Electrolytes

Fluids and Electrolytes. David A. Listman, MD St. Barnabas Hospital Pediatric Emergency Medicine. Goals and Objectives. Understand where fluid and salts are in body Understand and be able to order maintenance fluids Deficit fluids

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Fluids and Electrolytes

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  1. Fluids and Electrolytes David A. Listman, MD St. Barnabas Hospital Pediatric Emergency Medicine

  2. Goals and Objectives • Understand where fluid and salts are in body • Understand and be able to order • maintenance fluids • Deficit fluids • Be familiar with causes and treatment of hypo/ hyper- natremia • Provide fluids to patients in special circumstances

  3. Body Fluid Composition • Total body water (TBW) • 75-80% of body weight at birth • 60% of body weight after 1 year • Intracellular fluid • 2/3 of TBW or about 40% body weight • Extracellular fluid • 1/3 of TBW or about 20% body weight • ¾ Interstitial fluid • ¼ Plasma

  4. Need for Fluid Therapy • Maintenance of fluids in patients with insufficient intake (i.e.. NPO) • Replacement of already diminished fluid volume (i.e.. dehydration, trauma) • Replace ongoing losses (i.e.. GI, renal)

  5. Maintenance Fluids • Replacement of insensible losses due to heat dissipation • Replacement of Urinary Losses • Maintenance water needs are related to caloric requirement

  6. Maintenance Fluids • Caloric requirement • 100 kcal/kg/24hr up to 10 kg • 1000 kcal + • 50 kcal/kg/24hr per kg over 10 up to 20 • 1500 kcal + • 20 kcal/kg/24 hr per kg over 20

  7. Maintenance Fluids • Fluid requirement • 40 ml/100 kcal/ 24 hr to replace insensible losses • 60 ml/100 kcal/ 24 hr to replace urine losses • 100 ml/ 100 kcal/ 24 hours total • SO:

  8. Maintenance Fluids • Caloric requirement • 100 kcal/kg/24hr up to 10 kg • 1000 kcal + • 50 kcal/kg/24hr per kg over 10 up to 20 • 1500 kcal + • 20 kcal/kg/24 hr per kg over 20

  9. Maintenance Fluids • Fluid requirement • 100 ml/kg/24hr up to 10 kg • 1000 ml + • 50 ml/kg/24hr per kg over 10 up to 20 • 1500 ml + • 20 ml/kg/24 hr per kg over 20

  10. Maintenance Fluids • Fluid requirement • 100/ 50/ 20 • Divided by 24 hours (or 25) • 4 / 2/ 1 (cc’s per hour)

  11. Maintenance Fluids • Few examples: • 8 kg • 8 x 100 = 800 cc’s/ day • 800 / 24 = 33.3 cc’s/ hr or • 8 x 4 = 32 cc’s/ hr

  12. Maintenance Fluids • Few examples: • 18 kg • 10 x 100 = 1000 8 x 50 = 400 • 1000 + 400 = 1,400 cc’s/ day • 1,400 / 24 = 58.3 cc’s/ hr or • 10 x 4 = 40 8 x 2 = 16 • 40 + 16 = 56 cc’s/ hr

  13. Maintenance Fluids • Few examples: • 28 kg • 10 x 100 = 1000 10 x 50 = 500 8 x 20 = 160 • 1000 + 500 + 160 = 1,660 cc’s/ day • 1,660 / 24 = 69.2 cc’s/ hr or • 10 x 4 = 40 10 x 2 = 20 8 x 1 = 8 • 40 + 20 + 8 = 68 cc’s/ hr

  14. Maintenance fluids • We’ve got the water, do we need anything else? • Is it necessary to replace electrolytes? • Recent data shows significant risk of hyponatremia in hospitalized patients • Hyponatremia can lead to fluid shift into cells causing cellular (and cerebral) edema

  15. Maintenance fluids • Daily sodium requirement 2-4 meq / kg / day • Daily Potassium requirement 1-2 meq / kg / day This is a flat need per kilo and does not decrease as water needs do

  16. Maintenance fluids- sodium This is a flat need per kilo and does not decrease as water needs do So As volume required goes down, sodium needed per liter goes up

  17. Maintenance fluids- sodium Some examples- 10 kg child needs 20-40 meq Na+ per day 10 kg child needs 1000 cc’s per day 20-40 meq/ liter 20 kg child needs 40-80 meq Na+ per day 20 kg child needs 1500 cc’s per day 26-53 meq/ liter 50 kg child needs 100-200 meq Na+ per day 50 kg child needs 1800 cc’s per day 55-110 meq/liter

  18. Sodium concentrations • Normal saline (0.9% NaCl/L) 154 mEq Na+/L • 1/2 normal saline (0.45% NaCl/L) 77 mEq Na+/L • 1/3 normal saline (0.33% NaCl/L) 57 mEq Na+/L • 1/4normal saline (0.2% NaCl/L) 34 mEq Na+/L • Ringer’s lactate 130 mEq Na+/L (Contains 4 mEq K+, 109 mEq Cl-, 28 mEq bicarb equivalent all/Liter, and 3 mg/dl of Ca++)

  19. What else goes in it? • Dextrose • 5% dextrose is insufficient to nourish a patient • To spare catabolism of glycogen and protein

  20. What else goes in it? • Potassium • Daily requirement 1-2 meq/kg/day

  21. Need for Fluid Therapy • Maintenance of fluids in patients with insufficient intake (i.e.. NPO) • Replacement of already diminished fluid volume or deficit (i.e.. dehydration, trauma) • Replace ongoing losses (i.e.. GI, renal)

  22. Treatment of volume loss • Decrease in extracellular fluid • Initial treatment- rapid expansion of ECF • Bolus of isotonic fluid (i.e.. NS or LR) • Should not include dextrose • Repeat bolus as necessary to improve perfusion • Replacement of deficit • Continue maintenance • Frequent reevaluation of • Vital sign • Electrolytes • Urine output and urine specific gravity

  23. Treatment of volume loss • Decrease in extracellular fluid • Initial treatment- rapid expansion of ECF • Bolus of isotonic fluid (i.e.. NS or LR) • Repeat bolus as necessary to improve perfusion • Replacement of deficit • Continue maintenance • Frequent reevaluation of • Vital sign • Electrolytes • Urine output and urine specific gravity

  24. Estimate of Fluid Deficit • Subtract pre-illness weight - current weight • Calculate using current weight and % dehydration Pre-illness wt (kg)=100 Current wt (kg)100 - % estimated dehydration • Current Weight x % dehydration • (slightly underestimates)

  25. Estimate of Dehydration MildModerateSevere Skin Turgor Normal/Elastic ↓ Very ↓,Tenting Oral Mucosa Sl Dry Very Dry Parched Tears Sl ↓ Absent Absent Fontanelle Normal/ Flat Depressed Sunken Heart Rate Normal/ Sl ↑ ↑ Marked Tachycardia Blood Pressure Normal Normal/ Sl ↓ ↓ Urine OP Mild Oliguria Oliguria Oliguria/ Anuria CNS/ LOC Alert/ Responsive Irritable/Listless Minimal/Nonresponsive Pulse Quality Full Rapid Rapid/ weak Skin Warm/ Pink Cool/ Pale Cool

  26. Estimate of Dehydration Mild Moderate Severe <1yr 5% 10% 15% Older 3% 6% 9%

  27. Replacement of Deficit • Deficit volume • Replace ½ over 1st 8 hours • Replace ½ over next 16 hours • Don’t forget maintenance fluid

  28. Replacement of Deficit • Example- • 16 kg child 10% dehydrated • Bolus(es) normal saline 20 ml/kg rapidly • Maintenance 1,000 + 300= 1,300 / 24 = 54cc/hr • Deficit 1,600 ml • 800 over 1st 8 hours=100ml /hr • 800 over next 16 hours = 50ml /hr • Total 154 ml /hr x 8 hours then 104 ml/hr x16 hours • Not well approximated by 1 ½ maintenance

  29. Need for Fluid Therapy • Maintenance of fluids in patients with insufficient intake (i.e.. NPO) • Replacement of already diminished fluid volume or deficit (i.e.. dehydration, trauma) • Replace ongoing losses (i.e.. GI, renal)

  30. Ongoing losses • Continued loss in excess of normal maintenance • GI loss- vomit/ diarrhea • Surgical drains/ NG tube • Increased insensible losses- fever • Increased urine output

  31. Ongoing losses • Continued loss in excess of normal maintenance • Volume can often be measured • NG output • Stool • Urine • Type of fluid needed for replacement • Can be measured • Can be estimated

  32. Oral Rehydration • Better than IV if tolerated • What makes a good oral rehydration fluid? • Proper balance of Na+ and glucose • Na+/glucose co-transporter in intestine non ATP dependant • Water follows passively

  33. Oral Rehydration • What makes a good oral rehydration fluid? • Proper balance of Na+ and glucose • Na+/glucose co-transporter in intestine non ATP dependant • 1 : 1 osmolar ratio • Na+ 90 meq/l, glucose 111meq/l (2% solution) • Some K+ to prevent Hypokalemia

  34. Oral Rehydration • What makes a good oral rehydration fluid? MMWR November 21, 2003 / 52(RR16);1-16

  35. Oral Rehydration • Mild to moderate dehydration • Deficit 50-100 ml of ORS/kg body weight during 2-4 hours • Maintenance100 ml ORS/kg per day • limited volumes of fluid (e.g., 5 mL or 1 teaspoon) should be offered at first, with the amount gradually increased as tolerated.

  36. Hypo/ Hypernatremia • More to do with water than salt status (usually) • Hyponatremia • free water excess • Hypernatremia • Free water deficit

  37. Hyponatremia • Serum Na+ < 135 • Common in hospitalized children • Kidneys unable to dilute urine and excrete free water

  38. Hyponatremia • Measure serum Osm to confirm low serum Osm before aggressive treatment • Normal or high serum Osm with pseudohyponatremia • Hyperglycemia • Hyperlipidemia • Hyperproteinemia

  39. Hyponatremia • True hyponatremia causes influx of water into cells • Cellular swelling • Cerebral edema • Exacerbated by hypoxia

  40. Hyponatremia • Symptoms • Headache, nausea, vomit, behavioral changes • Seizures, resp arrest, dilated pupils, decorticate posturing

  41. Hyponatremia • Causes of SIADH • CNS • Meningitis • CNS neoplasm • Hydrocephalus • Pulmonary • Pneumonia • Asthma • TB • Positive Pressure Ventilation • Pneumothorax • Drugs • Vincristine, cyclophosphamide • Carbamazepine

  42. Hyponatremia • Post-operative • Multi-factorial • Volume depletion • Stress • ADH • Hypotonic fluids

  43. Hyponatremia • Water intoxication • Newborns • Fed dilute formula or water supplement • Decreased ability to maximally concentrate urine

  44. Hyponatremia- treatment • If neurologic signs/ seizure • Hypertonic 3% saline (514 meq/l) • 1 ml/kg/hr should raise Na+ by 1 meq/l • Goals • Raise Na+ by 1 meq/hr until • Symptoms resolve or • Serum Na+ has risen 20-25 meq/l or • Serum Na+ 125-130 meq/l

  45. Hyponatremia- treatment • Asymptomatic • Restrict free water intake • Avoid hypotonic fluids

  46. Hyponatremia • Recent evidence suggests use of isotonic rather than hypotonic fluids in post-op, gastroenteritis prevents hyponatremia.

  47. Hypernatremia • Serum Na+ >145 meq/l • Debilitated patients • Neurologically impaired patients • Ineffective breastfeeding • Inability to access sufficient free water • Inability to maximally concentrate urine

  48. Hypernatremia • Clinical manifestations • Water moves from intracellular to extracellular space • Maintenance of ECF volume so classic signs of volume depletion are absent • Agitation, irritability, coma

  49. Hypernatremia • Clinical manifestations • Water moves from intracellular to extracellular space • Cell shrinkage • Brain cell volume decreases • If acute and rapid can lead to • Intracranial hemorrhage • Venous sinus thrombosis • Over short time brain cells increase intracellular • Na+, K+, amino acids, unmeasured organic substances • Not easily decreased so rapid rehydration will cause cerebral edema

  50. Hypernatremia • Treatment • Correct serum Na+ and water deficit Free water deficit = 4ml x lean body weight (kg) x (serum Na+ – desired Na+ ) Add maintenance fluid and correct slowly • At least 48-72 hours if serum Na+ > 170

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