Fluids and Fluid Therapy

  1. total body water (TBW) in adults and neonates
    • Adults 50-70%
    • neonatals 80%.  Easy to over-hydrate
  2. factors affecting TBW
    age, body fat
  3. Distribution of TBW
    • 40% in intracellular space
    • 20% in extracellular space (15% interstitial, 5% intravascular)
  4. Body water solutes, particularly in ECF vs. ICF
    • Electrolytes become ions
    • cations = anions.  Balanced
    • cations in ECF are Na
    • cations in ICF are K and Mg
    • anions in ECF are Cl and HCO3 (bicarb)
    • anions in ICF are phosphates and proteins
    • ECF - Na, Cl, HCO3
    • ICF - K, Mg, phosphate, protein
  5. What is balanced therapeutic fluid?
    resembles ECF (Na, Cl, HCO3)
  6. milliequivalent
    • unit of measure expressing electrolyte concentration.  
    • 1:1000 of an equivalent weight (weight of element that will combine with 1 g of H+, gram molecular weight/positive valance)
  7. Osmolarity of dog/cat plasma or serum
    ~300 mOsm/L
  8. What shouldn't you do while administering calcium
    blood transfusion, calcium precipitates out red blood cells.
  9. Osmolality
    relative number of solute particles in 1 kg of solution.  More particles = more pressure
  10. Osmolarity
    number of solute particles per liter of solution
  11. osmotic pressure
    When effective solute particles attract water to cross a semipermeable membrane, the pressure required to stop them or the pressure until equilibrium is reached.
  12. effective vs. ineffective osmoles
    not all particles contribute to osmotic pressure.  Effective are Na and glucose, for example.  Albumin pulls water very well.  Ineffective are not clinically useful.
  13. tonicity
    total osmolarity or osmolality of a solution
  14. Isotonic fluid
    tonicity (effective osmolarity) approximately equal to tonicity of blood plasma
  15. hypotonic fluid
    • tonicity less than that of blood plasma.  
    • Fluid is pulled into ECF
  16. Hypertonic fluid
    • tonicity greater than that of blood plasma.  
    • Fluid is pulled into IVF (critical care patients, faster hydration from inside)
  17. Fluid disturbances in patients (3)
    • changes in volume (dehydration or blood loss)
    • changes in content (hyperkalemia in a blocked cat, etc)
    • changes in distribution (pleural effusion)
  18. dehydration and how you recognize it
    • hydration status, water loss>water intake.  
    • Check history (V? D? Bleeding?), physical exam (skin turgor, mucus membranes, heartbeat, pulses, breathing), MDB (basic tests)
    • Also check for ongoing fluid loss, and think of replacing electrolytes etc.
  19. Ways of taking food in
    • drinking water
    • water from ingested food (especially cats)
    • metabolic water
  20. ways of losing water
    • urine, feces, sweat (horses), respiration (dogs)
    • anorexia, PU, V, D, third spacing, extensive burns
    • includes sensible and insensible losses
  21. ISF deficits
    • early dehydration.  drop in skin turgor and dry mucous membranes.  
    • Weight or age of animals can affect skin turgor
  22. IVF deficits
    • more serious dehydration.  
    • hypotension (low BP), tachycardia, pale mucous membranes, increased CRT, weak pulse.  Increased skin turgor and dry membranes.
  23. ICF deficits
    • Massive dehydration leading to cerebral obtundation.  
    • Shock, nonresponsive, can't stand up or move.
  24. < 5% dehydration
    history of fluid loss but no findings in physical examination
  25. 5% dehydration
    dry oral mucous membranes but no panting or pathological tachycardia
  26. 7% dehydration
    mild to moderate decreased skin turgor, dry oral mucous membranes, slight tachycardia, and normal pulse pressure
  27. 10% dehydration
    moderate to marked degree of decreased skin turgor, dry oral mucous membranes, tachycardia, and decreased pulse pressure
  28. 12% dehydration
    marked loss of skin turgor, dry oral mucous membranes and significant signs of shock.
  29. Three things you need to calculate amount if IV fluid to administer
    • Hydration deficit
    • maintenance requirements
    • ongoing losses
  30. hydration deficit
    • amount of fluid that must be replaced to bring animal back to normal hydration status.  
    • %dehydration x body weight = lbs of fluid lost.
    • 500mL = 1 lb
    • Use 75% over 24 hours because this is an ESTIMATE
    • (add to maintenance requirement and ongoing loss to replace)
  31. mL to lb conversion
    500mL to 1 lb
  32. Maintenance requirements, traditional method
    • Volume of fluid needed to replace normal sensible and insensible losses.  
    • 30mL/lb/day.  
    • (add to hydration deficit and ongoing losses to replace)
  33. alternate calculation of maintenance requirements, or wheel maintenance
    30 x kg +70 = mL
  34. new AAHA maintenance
    • cat = 80 x kg0.75 = 2-3 ml/kg/hr
    • dog = 132 x kg0.75 = 2-6 ml/kg/hr
  35. Blood volume in cats and dogs and why it's important
    • don't bolus more than the blood volume per hour.  
    • cat = 40-60 ml/kg
    • dog = 90 ml/kg
    • Bolus in 25% increments, 15 minutes at a time.
  36. Ongoing or continuing abnormal losses
    • Estimated fluid losses from vomiting, diarrhea and/or excessive urination.  
    • Add to hydration deficit and maintenance requirement.  
    • Administer CRI over 24 hours.
  37. drip rate equation
    gtt/min = (volume of infusion)/(time of infusion) x drip factor
  38. fluid therapy routes of administration, and how you choose
    • condition being treated, duration of condition and severity of condition
    • IV, SQ, PO, IP, IO
  39. IV fluid administration
    • quickest and most precise
    • requires IV catheter
    • Preferred with significant fluid loss or severe condition
  40. SC
    • For less severe needs
    • Amount depends on animal size, usu 5-10mL/lb per injection site
    • Use Isotonic fluids
  41. PO
    • can't use in severe GI disorders
    • Allows normal physiological processes to control amount
    • not good for large volumes
  42. IP
    • can administer a large volume but absorption is slow
    • Rarely used
  43. IO
    • very small animals or poor venous access
    • rapid delivery of fluids
    • requires expertise in placing IO needle.
  44. Ways to monitor fluid administration
    • physical status: weight, skin turgor, mm/crt, lung sounds, oculonasal discharge, urine output
    • laboratory: PCV/TP, CVP
  45. CVP
    central venous pressure.
  46. To judge central venous pressure
    • requires placement of jugular catheter.  
    • Extension set, stopcock, manometer, saline.  
    • Hold "O" of manometer at level of heart.  Optimal is 5-8 cm H2O.  <5 insufficient.  > 14 overload.  
    • Fluctuates with respiration.
  47. clinical signs of overhydration
    • restlessness
    • serous oculonasal dishcharge
    • crackles
    • tachycardia
    • dyspnea
    • pitting edema
    • inappropriate weight gain
  48. Selection of fluids
    • give fluids that most closely resemble what has been lost
    • Give in body compartment where fluid deficit lies
  49. Crystalloids
    • true solutions containing small molecular weight particles that can move through pores in capillary walls.  
    • Particles can also move slowly through cell membranes
    • Includes electrolytes, buffers and/or dextrose
  50. Balanced crystalloids vs non-balanced crystalloids
    • balanced contain electrolytes in approx same concentrations as blood plasma
    • balanced also are fluids containing buffers (lactate, acetate or gluconate)
    • non-balanced do not resemble composition of blood plasma or ICF
  51. balanced crystalloids examples
    • LRS
    • Normosol-R
    • Plasmalyte
  52. LRS
    • balanced crystalloid
    • replacement solution
    • buffer is lactate (converted by liver to bicarb, buffers against acidosis)
    • do not administer with blood
  53. Normosol-R
    • balanced crystalloid replacement solution
    • dual buffer of acetate and gluconate (metabolized outside liver, precursers to bicarb)
    • Can be administered with blood.
  54. Plasmalyte
    balanced crystalloid replacement solutiondual buffer of acetate and gluconate (metabolized outside liver, precursers to bicarb)Can be administered with blood.
  55. unbalanced crystalloid examples
    • D5W
    • 0.9% NaCl
    • 2.5% dextrose + 0.45% NaCl
  56. D5W
    • Unbalanced crystalloid
    • contains dextrose at 5g/L and water
    • dextrose metabolized to H2O and CO2
    • Not given SQ
    • not used for maintinence
  57. 0.9% NaCl
    • Isotonic saline, unbalanced crystalloid
    • Indications: hyperkalemia, increases plasma volume, Na deficiency, bathe tissues intraop
    • Contraindicated in heart disease
    • Not used for maintinence
  58. 2.5% dextrose and 0.45% NaCl
    • "half-strength" saline, unbalanced crystalloid
    • Indicated for patients with Na restrictions (Heart disease, renal disease, hypertension)
    • maintinence okay with KCl added
  59. Colloids
    • contain large molecular weight molecules unable to cross cell membranes
    • used to increase oncotic pressure (osmotic pressure exerted by colloids in blood plasma)
    • AKA plasma volume expanders
  60. plasma volume expanders
  61. when to administer colloids
    • patients with large volume losses where crystalloids are not improving/maintaining blood volume
    • When increased O2 or tissue perfusion needed
    • If edema develops before blood volume restoration
    • decreased oncotic pressure (TP<3.5 or alb<1.5g/dL)
    • for longer duration of effect
    • difficult to administer in sufficient amount for resuscitation
    • goal is least volume with highest CV benefit
  62. natural colloids
    • whole blood, plasma, albumin
    • Choose depending on animal problem--whole blood or fresh frozen plasma for coagulation factors, whole blood or packed RBCs for blood cells.  
    • Adverse reactions include bleeding, vomiting, fever, urticaria (rash, hives), facial edema and others
  63. synthetic colloids
    • Plasma volume expanders (administer slowly)
    • Dextran 70 (polysaccharide, can cause allergic reaction or clotting deficits)
    • Hetastarch (Hespan) (from maize, hydroxyethyl starch, less antigenic than dextran, expensive)
  64. Dextran 70
    • synthetic colloid, plasma volume expander.  Administer slowly.  
    • Polysaccharide solution
    • can cause allergic reactions or clotting deficits
  65. Hetastarch (Hespan)
    • derived from maize (hydroxyethyl starch)
    • less antigenic than dextran
    • expensive
  66. oxyglobin
    • modified biological colloid
    • ultrapure, bovine-origin polymerized hemoglobin solution (for dogs with anemia)
    • O2 carrying substitute for RBCs, temporary, universal compatability
    • stored at room temp (2 yr shelf life, opened 24hr expiration)
    • adverse reactions include pulmonary edema, V/D, yellow-orange skin discoloration of skin, urine serum, sclera etc.
  67. Common additives to fluids
    • potassium chloride
    • 50% dextrose
    • Vitamin B complex
  68. Potassium chloride
    • common additive, prevents k deficits
    • Usu 2 mEq/ml
    • amount added depends on serum k level
    • adverse effects include muscle weakness and cardiac conduction (hyperkalemia)
  69. 50% dextrose
    common additive for hypoglycemic patients or ketosis in ruminants
  70. Vitamin B complex
    • common additive, water soluble vitamins which are lost in animals with diuresis
    • Generally add 2mL/L
    • adverse include hypersensitivity (thiamine)
Card Set
Fluids and Fluid Therapy
Fluids and fluid therapy in pharm and tox