electrolytes Flashcards
define osmolality
physical property of solutoin based on concentration solutes per kilogram of solvent
describe the clinical significance of osmolality
- the parameter to which hypothalamus response
- regulation of osmolality affects plasma sodium concentration
- regulation of sodium and water controls blood volume
how does AVP affect osmolality
AVP increases water retention in kidney, lowering osmolality
- drinking water increases extracellular water -> dilutes out salutes -> decreases osmolality
how is osmolality calculated
2(Na)+(glucose/20)+(BUN/3)
define osmolal gap
difference between calculated and determined osmolality - should be less than 5-10
describe sodium in the body
- most abundant cation (90% of cation [])
- higher concentration outside of cells
- regulated by sodium potassium pumps in response to osmol changes
what is sodiums reference range
135-145 mmol/L
describe the role of potassium in the body
- major intracellular cation (20 times greater w/in cell)
- regulated by kidney
- neuromuscular excitability
- heart contractions
what is the reference range for potassium
3.5-5.1 mmol/L
describe chlorides purpose in the body
- major extracellular anaion
- maintains osmolality, blood vol and electric neutrality
- RR: 98-107
describe bicarb in the body (electrolyte version)
- second most abundant anion in ECF
- major part of buffering system in blood
- exchanged for chloride in cell excretion of CO2
describe magnesium
- fourth most abundant
- mostly in bones/muscles
- free magnesium acts as cofactor and are physiologically active
- regulated by kidneys
describe the importance of calcium
- essential for myocardial contraction
- found in blood and other ECF at 1% of total vol
- increased vols in response to: PTH, vitamin D
- decreased from: calcitonin
how does PTH impact calcium levels
- in bone stimulates osteoclast activity to release calcium
- in kidney promotes reabsorption of calcium
- activates vitamin D to bolster effects in bone marrow
what is the calcium reference range
2.24-2.53 mmol/L
how can hypomagnesemia impact calcium levels
- inhibits secretion of PTH
- impairs PTH action
- causes vitamin D resistance
describe lactate
- by product of emergency ATP production
- used in metabolic monitoring over ammonia
define anion gap
the difference between unmeasured anions in solution and unmeasured cations
what is anion gap useful for
indicating increase in one or more unmeasured anions in serum
how is anion gap calculated and what is the reference range
- [Na+K]-[Cl+HCO3]
- 10-20 mmol/L
how is chloride reabsorbed
passive transport in proximal tubule
how does ANP (atrial natriuretic peptide) effect blood vol
released from heart in response to hypervolemia to increase salt and water excretion
how are sodium and water linked in regards to blood volume
where sodium goes, water follows
