Body Fluid Compartments Flashcards
Organs that communicate ECF to external environment (4)
- Skin
- Lungs
- Kidneys
4 Alimentary Canal
Transcellular Fluid Compartment
Consists of fluid in transit to epithelia, CSF, and intraocular fluid
~2-4% of TBW
Major ECF ions
Na+ and Cl-
Major ICF ion
K+
Osmolarity calculation
2[Na+]+[Glucose]/18+[BUN]/2.8
Characteristics of Dilution Substance
- Nontoxic
2 Neither synthesized or metabolized
- Does not cause shifts in fluid distribution
Plasma Volume Determination
Iodized albumin is added to the plasma (does not cross capillary walls)
Use PV= [Amount of albumin]/[conc. of injected albumin]
ECF Volume Determination
Used inulin (does not penetrate cell membranes, will permeate thru capillary)
*Some is lost in kidneys so must factor that into equation
TBW Determination
Use antipyrine or tritiated water
- Permeates uniformly thru all compartments
- Can be lost via every open route
ISF Calculation
V(ECF)-PV
V(ICF) Calculation
V(ICF)= TBW-V(ECF)
Isosmotic Water Shifts
Change in ECF volume only
*Can occur after infusion of normal saline
(42x300 + volume insertedx300)= final osmolality
Hyperosmotic Water Shifts
Occurs thru decreases in TBW(sweating, decreased ADH) or increased [Na+] (ingestion of salt tablets, infusion of NaCl)
Symptoms: Lethargy, weakness, twitching, seizures, possible death (altered electrical activity)
*Symptoms related to rupture of cerebral veins due to water moving out of brain cells
Hyposmotic Water Shifts
Due to increased TBW (SIADH from pulmonary disease or drugs, excessive thirst) or decreased [Na+] (decreased aldosterone)
Symptoms: Nausea, headache, lethargy, PERMANENT neurologic deficits (low electrical activity)
- premenopausal women at highest risk for poor recovery
- Chronic symptoms are alleviated because water can flow out of the brain ISF into the CSF decreasing edema
Equivalence
(grams/L)/molecular weight X valence
