Update on fluid therapy in horses (Proceedings)

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Update on fluid therapy in horses (Proceedings)

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Aug 01, 2010

Fluid Plans

     •Replacement: Determining Rate
     • New : 'Fluid Challenge' Method:
     • Volumes are based on "fluid challenges" rather 'estimates' of deficits
     • Traditional method is with estimates of % of water loss
          o Riddled with errors....

"Fluid Challenge Method"

     • 20 mL/kg boluses of isotonic crystalloid over 30-60 minutes, then reassess for more
          o Repeat boluses until signs of shock abate or plateau, or until limits reached, indicating the need for vasopressors
          o 10 L for an average adult horse
          o 1 L for average neonatal foal

Fluid Challenge for Colloids

     • Lower rates because they stay within the vascular space
          o 3-10 mL/kg hetastarch

How much to give?

Base it on Clinical response

     • Mentation
          o Increase alertness
          o Foal that is kicking is rarely severely hypovolemic
     • Urination
          o In general, sufficient fluids have been given when the horse/foal begins to pass urine
     • Decrease heart rate
     • Improvement in membrane color or capillary refill
     • In hospital= blood pressure (> 60 mmHg in foal, 80 in adult)

Crystalloids vs. Colloids?

     • Crystalloids only contain electrolytes or glucose in water
     • Colloids contain large MW particles
          o Proteins or synthetic polysaccharides
     • Human studies fail to show an advantage of 1 over the other
          o Use together may be ideal
     • Isotonic crystalloids hydrate entire ECF
          o 25 % to plasma volume; 75 % to interstitium
     • Colloids expand the intravascular space only
     • Rapid expansion of plasma volume
     • Large particles stay within vessels
     • Colloids are better in horses concurrently hypovolemic and hypooncotic

Replacement Crystalloids

     • Choices:
          o Lactated Ringer's Solution (LRS)
          o Normosol-R
          o Plasma-Lyte 148 or A
          o Normal saline (0.9%)