Fluids and electrolytes Flashcards
Water percentages in different ages
Infant= 70%
Adult= 60%
Elderly= 50-55%
Fluid balance
Two types of water losses
Intake= output= fluid balance
Sensible losses
-urination
-defecation
-wound drainage
Insensible losses (no way to measure it)
-evaporation from skin
-respiratory loss from lungs
2 types of transport systems
Passive eg diffusion, filtration, osmosis
Active eg. pumping, active transport
Sodium
-major extracellular cation
-attracts fluid and helps preserve fluid volume
-combines with chloride and bicarbonate to regulate acid-base balance
Sodium potassium pump
-Na moves into cells
-K moves out of cells
-uses ATP, Mg and an enzyme to maintain Na, K concentrations
-pump prevents swelling and creates small charge, allowing neuromuscular impulse transmission
Low sodium blood levels and how it occurs
Hyponatremia
Occurs by:
-dilutional- Na+ loss, water gain
-depletional- insufficient Na+ intake
-hypovolemic- Na+ loss is greater than water loss, can be renal eg diuretic, non renal eg vomiting
-hypervolemic- water gain greater than Na+ gain, oedema occurs
-Isovolumic- normal Na+ level, too much fluid
High sodium blood levels
Hypernatremia
-occurs less often than hyponatremia
-thirst is the body’s main defence
-excess Na+ relative to water
-water deficit or over ingestion of Na+
-causes fluid to shift out of cells
Potassium
-major intracellular cation
-changes in K+ levels can lead to serious neuromuscular/ cardiac problems
-majority is excreted by kidneys
Controlled by:
Na+/K+ pump
Renal regulation
pH levels
How is pH controlled in cells
-H+ and K+ exchange freely across the membrane
Acidosis= hyperkalemia= K+ out of cells
Alkalosis=hypokalemia= K+ into cells
Cl-
-extracellular anion
-Na+ and Cl- regulate water
-secreted by stomach as HCl
-aids CO2 transport in blood
HCO3-
-extracellular anion
-concentration increases in blood passing systematic capillaries picking up CO2
CO2+ H2O -> H2CO3
H2CO3 -> H+ + HCO3-
-HCO3- levels drop in pulmonary capillaries when CO2 exhaled
How fluid balance is maintained
(Tissue fluid formed)
-fluid movement between capillaries and interstitial tissue governed by net filtration pressure
-Net filtration pressure= hydrostatic pressure (blood pressure) and osmotic pressure (takes place due to differing concentrations)
-High hydrostatic pressure pushes fluid out the capillaries at arterial end via filtration
-High osmotic pressure causes fluid to re enter the capillary at the venous end
-osmotic pressure is caused by the plasma proteins which are too big to leave the capillaries, causing a higher concentration inside the capillary
3 fluid types
Hypertonic- high solute concentration, fluid moves out cells, cells shrink
Isotonic- no fluid shifts, solutions are equally concentrated
Hypotonic- low solute conc, fluid moves from hypotonic solution into cells, causing them to swell
What can cause fluid imbalances
-dehydration
-hypovolemia- body loses too much fluid
-hypervolemia- body doesn’t lose enough fluid, too much kept in the body, can cause oedema
-water intoxication
Patients at risk from dehydration
confused
comatose- in a coma
bedridden
elderly
infants
enterally fed- feeding tube
