9) Body water and electrolytes Flashcards
list main body cations
sodium
potassium
calcium
magnesium
trace elements
list main body anions
chloride
bicarbonate
proteins (albumin)
organic acids (lactate)
sulfate
phosphate
main intracellular ions
K+
phosphate
proteins
main extracellular ions
Na+
Cl-
HCO3-
proteins
Na+ functions
Maintains osmolality
Regulates acid-base balance by Na-H exchange in kidneys
K+ functions
Involved in heart and skeletal muscle contraction
Maintains intracellular osmolality
Influences acid-base balance
80% plasma osmolality is due to…
Na and Cl
chloride functions
Maintains plasma osmolality with sodium
Chloride shift (Maintains electroneutrality when Cl- exchanges with HCO3-)
Test used to diagnose children with Cystic Fibrosis
sweat chloride
> 60 mmol/L chloride is positive for…
CF
———- and the agent ——– is used to stimulate sweat production on the skin of a child
Iontophoresis
pilocarpine
how does hemolysis affect electrolyte measures?
Increased Potassium
Increased Phosphorus
Increased Iron
Increased Magnesium
Increased AST, ALT, CK, Troponin, and LD (liver & cardiac enzymes)
calculate anion gap
AG = [Na + K] - [Cl + HCO3]
or
AG = AG = Na - [Cl + HCO3]
causes of increased AG (not mudpiles)
- Renal Tubular Disease
- Diabetic Ketoacidosis
causes of low AG
- low albumin (most common)
- Organic paraproteins
- Inorganic bromide, lithium, Iodine, or Polymyxin B
MUDPILES
causes of high AG
- methanol
- uremia
- DM
- paraldehyde
- isoniazid
- lactic acidosis
- ethylene glycol/ethanol
- salicylate
major difference between plasma and ISF
presence of protein in plasma and virtually none in ISF
Represents a heterogeneous mixture of solutes that are difficult to measure directly because of the lack of cells free of contamination
intracellular water compartment
interactions of physical forces within and among fluid compartments
Gibbs-Donnan equilibrium
Used to identify the number of moles of a particle per kilogram of water, not the kind of particle
osmolality
Solution concentrations expressed on a weight factor are ——— independent
temperature
As osmolality increases…
- Osmotic pressure
- Boiling point
- Freezing point
- Vapor pressure
increases
increases
decreases
decreases
explain how the freezing point osmometer works
- Sample is rapidly supercooled to several degrees below its freezing point.
- Then agitated with the stirrer to initiate freezing.
- Rate at which this heat of fusion is released from the ice being rapidly formed reaches equilibrium with the rate of heat removed.
The freezing point is lowered by an amount that is directly proportional to…
the concentration of dissolved particles in the solution
osmolality equation
mOsm/kg = (1.86)(Na) + (Glucose/18) + (BUN/2.8) + 9
osmol gap
osmol gap = measured osm - calculated osm
the causes of high osmol gap and AG are basically the same, except…
salicylate poisoning does not cause high osmol gap
Pressure created in a solution by the presence of large (> 30 kDa) proteins, also called colloids.
colloid oncotic pressure
hypothalamus responds to these stimuli in order to regulate water balance
Increases in extracellular water osmolarity
Decreases in intravascular volume
Angiotensin II
angiotensin II effect on transport
increases NaCl and H2O reabsorption
aldosterone effect on transpoart
increases NaCl and H2O reabsorption
ANP, BNP, CNP effect on transport
inhibits NaCl and H2O reabsorption
urodilantin effect on transport
inhibits NaCl and H2O reabsorption
ADH effect on transport
Increases H2O reabsorption
Causes increased thirst and water intake
thirst center
Stimulates the posterior pituitary gland to secrete Antidiuretic Hormone (ADH)
antidiuretic center
2 areas of hypothalamus responding to low water
thirst center (water intake)
antidiuretic center (water output)