* L03-Body fluids Flashcards
what are the hydrostatic pressures within the capillarys at the arterial and venous ends?
32mmhg at the arterial end
12mmhg at the venous end
what is the oncotic pressure in the capillaries
25mmhg
what is the typical value for balanced water intake and output in the body daily?
2,400ml
what are the most important ions in the body fluids intracellularly and extracellularly?
potassium intracellularly
sodium extracellularly
why do losses of K+ from the body have only a small effect on plasma k+ concentration?
k+ can move out of the cells to maintain equilibrium between intracellular and extracellular fluid
what is a simple method for measuring body fluid compartments?
add a substance that uniformally distributes throughout the body compartment. then use colourimetry to measure the concentration of the substance, this will allow you to calculate the volume by dividing the amount of substance over the concentration.
what is the volume of distribution equation?
volume of distribution = (quantity administered)-(quantity metabolised or lost)/concentration
how is plasma volume typically measured?
need a substance that doesnt cross the capillaries so typically use labelled plasma proteins. then can calculate volume by measuring concentration of the protein after a known amount has been injected
which substance is used to measure extracellular fluid volume?
thiosulphate is typically used as it can readily cross between plasma, interstitial fluid and transcellular fluid (joint capsules etc) but doesnt enter cells
Give examples of transcellular spaces?
peritoneal space
CSF
Pleural cavity
sinovial fluid
What is the definition for volume of distribution?
The volume of fluid required to contain the total amount of drug in the body at the same concentration as that present in the plasma
What is hematocrit and what is a typical hematocrit?
Hematocrit is the proportion of volume of red blood cells to total blood volume and has a typical value of 45%
In what state is Ca2+ present in the blood?
Around half is free in the blood and half is bound to albumin so if the albumin conc changes then this can change Ca2+
What is the difference between osmolality and osmolarity?
osmolality is the number of osmoles per unit mass of the solvent
osmolarity is the number of osmoles per unit volume of the solution
What is the use of mannitol and how does it achieve this?
It can be used to decrease intracranial pressure or as an osmotic diuretic. This is because it increases the plasma osmolality when injected intravenously, this causes water to move out of cells.
