Vetpocket Iv Fluid Therapy Guidelines For Dogs And Cats

Excerpt

Fluid Compartments
• -60% of an adult dog or cats total (lean) body weight is TBW.
• TBW is distributed between two main fluid compartments, -67% ICF and -33% ECF.
• ECF is distributed between -25% intravascular fluid and -75% extravascular fluid.
• Extravascular fluid is distributed between interstitial fluid (-74% of ECF) and trans-
cellular fluid (-1% of ECF). ICF is also extravascular fluid.
• Fluid moves between the two ECF compartments (intravascular and interstitial fluid
compartments) because of Starling’s law of the capillary and osmosis.
• Fluid moves between the ECF and ICF compartments by osmosis.
• In the ECF (intravascular and interstitial fluid), Na' is the main cation and Cl the main
anion. In the ICF, K' is the main cation (most of the body K* is found intracellularly).
• 60:40:20 rule: -60% of total body weight is TBW: -40% of total body weight is ICF: -20% of total body weight is ECF.
Total body water (TBW)
(-60% of total body weight)
Intracellular fluid (ICF)
Extracellular fluid (ECF)
-67% of TBW
(-40% of total body weight)
-33% of TBW
(-20% of total body weight)
Intravascular fluid
-25% of ECF
(-5% of total bod> weight)
Extravascular fluid
-75% of ECF
(-15% of total body weight)
Interstitial fluid Transcellular fluid
-74% of ECF
-1% of ECF
(-15% of total body weight) (~<1% of total body weight)
• Fluid compartments are separated by membranes. The capillary membrane is permeable
to water and small molecular weight solutes. The cell membrane is permeable to water, but
carefully controls permeability of solutes by utilizing transport mechanisms.
Intracellular fluid (ICF) -----------------------------------
Cell membrane
Interstitial fluid
Capillary membrane
Intravascular fluid
— Extravascular fluid
— Extracellular fluld(ECF)
• Starling's law of the capillary: fluid filtration and solute diffusion across a capillary
membrane is dependent on the balance between the hydrostatic and oncotic pressure
gradients across the capillary, as well