Fluid Therapy Flashcards
What percent of body weight is water
60%
Pediatric: maybe 70%
Obese: use lean body weight for calculations (lean body weight is 70% of BW)
In dogs and cats, what percent of total body water is intracellular vs extracellular
Intracellular: 2/3 of TBW (40% BW)
Extracellular water: 1/3 of TBW (20% BW)
within this, interstitial water is 75% of ECF and intravascular water is 25% of ECF
Extracellular water is approx 1/3 of total body water (or 20% of body weight), what are its further subdivisions
Interstitial water: 75% of ECF
Intravascular water: 25% of ECF
2/3 of the total body water is _____________ (40% of body weight)
intracellular fluid
1/3 of the total body water is ____________ (20% of body weight)
extracellular fluid
If you have a 10kg dog. What is:
-TBW
-Intracellular fluid water
-Extracellular fluid water
-Interstitial Fluid Water
-Intravascular fluid
TBW: 0.6 x 10= 6kg
Intracellular: 2/3 of 6 L= 4L
Extracellular: 1/3 of 6L = 2L
Interstitial: 3/4 of ECF= 1.5L
Intravascular= 1/4 of ECF = 0.5L (1/12 of TBW)
About what percent of the body weight is blood volume
8-9% of BW in dogs
5-6% of BW in cats
Intravascular fluid water volume is about 5% of the body weight, why is the blood volume 8-9% of TBW and 5-6% of the body weight in cats?
Because blood contains both a liquid phase (plasma) and a cellular phase (RBC)
-IV water volume takes only the liquid phase into acocunt
If you have a 30kg dog. What is:
-TBW
-Intracellular fluid water
-Extracellular fluid water
-Interstitial Fluid Water
-Intravascular fluid
TBW= 0.6xBW= 18L
ICF: 0.67xTBW= 12L
ECF: 0.33xTBW= 6L
Intravenous Water (plasma) volume= 0.25xECF = 0.25x 6= 1.5L
Interstitial fluid volume= 0.75xECF= 0.75x6=4.5L
If you have a 5kg cat. What is:
-TBW
-Intracellular fluid water
-Extracellular fluid water
-Interstitial Fluid Water
-Intravascular fluid
TBW= 0.6xBW= 3L
ICF: 0.67xTBW= 2L
ECF: 0.33xTBW= 1L
Intravenous Water (plasma) volume= 0.25xECF = 0.25x 1= 0.250L
Interstitial fluid volume= 0.75xECF= 0.75x1=0.750L
Barrier between ICF and ECF compartments
Semi-permeable cell membrane
Freely permeable to water based on concentration gradients
Impermeable to electrolytes and proteins unless by transport
*Fluid move because of osmotic forces
How is fluid moved between ICF and ECF
Fluid move because of osmotic forces
Semi-permeable cell membrane
Freely permeable to water based on concentration gradients
Impermeable to electrolytes and proteins unless by transport
How is fluid moved within the ECF- between Int and IV
*Fluid moved because of Starling forces
-Endothelium
-freely permeable to electrolytes based on concentration gradients- water will follow
-relatively impermeable to proteins, larger molecules
Osmolality is proportional to
the number of non dissociable ions in a given solution
-not a function of the size or the molecular weight of the ion, just the number
expressed as mOsm/kg
How do you calculate osmolarity
2(NA +K) + BUN (mg/dL)/2.8 + Glucose (mg/dL)/18
Normal values are 280-305mOsm/L for dogs and 95-320 mOsm/L for cats
Is potassium higher ICF or ECF
ICF
Is Na+ higher ICF or ECF
ECF
Is Mg2++ higher ICF or ECF
ICF
Is Cl- higher ICF or ECF
ECF
What allows for movement of K+ out of cell and Na+ into the cell
Na/K ATPase
Effective osmoles
generate osmotic pressure across a semi-permeable membrane that is not permeable to that particle
*will result in movement of water
*Determines the tonicity of that compartment
ex: Sodium, Potassium
Why does albumin have minimal effect on osmolality
because its molecular weight is very high (66,000 Da) which makes the particle number relatively low
*We use colloid osmotic pressure, also known as oncotic pressure, refers to the osmolality due to proteins
Ineffective osmoles
have osmotic potential but they are unable to diffuse across the barrier
No osmotic pressure is generated, no movement of water
contributes to total osmolality but not tonicity
ex: Urea (diffusible), glucose (metabolized)
Note: D5W is iso-osmolar AND hypotonic
What are Starling’s forces
determine the movement of water between the interstitial fluid compartment and the intravascular fluid compartment, within the ECF
1) Oncotic pressure
2) Hydrostatic pressure
3) Vascular permeability
4) Lymphatic drainage