Fluid Flashcards
How much of our body composed of water
60%
Makes body weight sensitive to fluid status
3 spaces within the ECF
Interstitial (around cell out of vessel)
Intravascular (in BVs)
Transcellular (third spacing)
The proper distribution of water among body compartments is strongly related to what?
The number of osmoles present in the ECF
Osmoles
Drawl water into its direction
Normal concentration of osmoles in the ECF is
275-295
How do we assess fluid and electrolyte status?
Blood sample
Test the liquid components of blood (plasma and serum)
Plasma
Liquid component of blood
Plasma proteins and all other particles dissolved in the blood
Serum
Liquid component of blood
Remains in the blood sample after a blood clot is allowed to form
Does not contain:
The coagulation proteins used to form the clot
Does contain :
-Other plasma proteins (antibodies, hormones)
-Dissolved particles (glucose, electrolytes, O2 & CO2)
Osmolarity vs osmolality
Osmolarity: miliosmoles per liter (IV solutions)
Osmolality: milliosmoles per Kilogram (human body)
Osmosis
Movement of water across a semipermeable membrane
Plasma membranes of cells are:
Freely permeable to water
Relatively impermeable to sodium
When osmolality is off look at what three things
Na
Glucose
BUN
Normal serum sodium
140
Sodium x 2 = osmolality (140x2=280)
Isotonic
Same as normal, healthy plasma
Normal osmolality=275-295
Hypotonic
ECF tonicity too low
Swells cell
Hypertonic
ECF tonicity too high
Cell shrinks
Edema
Collection of fluid in the Interstitial space
Fluid moves in and out of capillaries (governed by “Starlings Law of the Capillaries)
Colloid
Large molecular weight particles (proteins)
Do not dissolve in water
Crystalloid
Particles that dissolve when added to water to form a true solution
Hydrostatic pressure (fluid pressure) vs osmotic pressure
Hydrostatic pressure: fluid pushing outward on the vessels
*force favoring filtration/pushing fluid out
Osmotic pressure : proteins (colloids that cause a pulling force causing pressure
*force favoring reabsorption/pulling fluid in
What does the lymph system do in the starlings law of the cappilaries
Drawls in the extra fluid
Mechanisms of edema formation
1) increased capillary hydrostatic pressure (BP)
2) decreased capillary colloid osmotic pressure (decreased proteins=cant reabsorb)
3) increased capillary permeability (inflammation, allows more things to leave)
4) obstruction of lymphatic flow (called lymphedema) skin of an orange
Third spacing
Fluid shifting into transcellular spaces
Ascites (peritoneal cavity)
Pleural effusions (pleural space)
Pericardial effusions (pericardial space)
Antidiuretic Hormones (Arginine Vasopressin)
Triggers retention of water by pores
travels thru blood to kidneys to increase retention of water bu inserting more awuaporin proteins into renal tubule cells
Pathophysiologic conditions of ADH secretion
Diabetes insipidus (arginine vasopressin deficiency)
Syndrome of inappropriate ADH (SIADH)
