Body Fluids Flashcards
What is osmolarity?
mOsm (milliosmoles)/L =
concentration of particles per liter of solution.
What is osmolality?
mOsm/kg = concentration of
particles per kg solvent (water in biological systems)
What is an effective osmole?
Refers to a solute that does not easily cross a membrane.
It is an effective osmole because it creates an osmotic force for water.
Proteins are effective osmoles for the vascular compartment
What is the average daily intake of water breakdown?
• Ingestion (fluids or food): • 2100 ml/day • Metabolism: • 200 ml/day Total Daily Intake: 2300 ml/day
What is the average daily loss of water breakdown?
• Insensible evaporation:
• 350 ml/day through skin (3-5 liters/day for severe burns)
• 350 ml/day via lungs
• Sweat:
• 100 ml/day (5000 ml/day during exercise)
• Feces:
• 100 ml/day
• Urine:
• 1400 ml/day (500 ml/day during exercise)
Total Daily Loss: 2300 ml/day
What is the total body water?
42 liters (70 kg male)
• 50% body weight in females because of more body fat
• 70-75% body weight in premature and newborn
What is the osmolar gap?
(helps to narrow the differential diagnosis)
• Difference between the measured osmolality and the estimated osmolality (Normal ≤ 15)
• ECF Effective osmolality = 2(Na+) mEq/L + (glucose mg%/18) + (urea mg%/2.8)
What are some common things that can elevate the osmolar gap?
- Ethanol
- Methanol
- Ethylene glycol
- Acetone
- Mannitol
What is the intracellular fluid composition?
- Small amounts of sodium and chloride ions
- Almost no calcium ions
- Large amounts of potassium and phosphate ions
- Moderate amounts of magnesium and sulphate ions
True or false plasma has a higher concentration of proteins because capillaries have a low permeability to plasma proteins.
True
True or false, ionic composition of plasma and interstitial fluid is similar.
True, because they are separated by highly permeable capillary membranes.
Indicator-Dilution Principle
• Applies to measurement of fluid volumes in body
fluid compartments.
• Requirements for an indicator:
• Disperses evenly throughout compartment
• Disperses only in compartment being measured
• Not metabolized or excreted
• Not toxic
Vol B = Vol A x conc. A / conc. B
What are the relative amounts of extracellular fluids in interstitial spaces and plasma determined primarily by?
the balance of hydrostatic and colloid forces across
capillary membranes
What is the distribution of fluid between intracellular and
extracellular compartments determined mostly by?
osmotic effects primarily of sodium and chloride
ions.
How much osmotic pressure is exerted across the cell membrane for each mOsm concentration gradient of an
impermeant solute?
about 19.3 mm Hg