state of equilibrium in the internal environment of the body
maintenance of the composition and volume of body fluids within narrow limits of normal is necessary
Adult percentage of water
50-60%
is greater in men=more lean body mass
older adult / infant percentage of water
45-55% / 70-80% (respectively)
both are at higher risk for fluid related problems
2 major compartments of fluid in the body
intracellular
extracellular
intracellular space
inside the cell
2/3 of body water is located here
extracellular space
interstitial fluid- fluid in the interstitium(space btwn the cells) and lymph
intravacular- fluid in blood(plasma)
transcellular fluid- fluid in specialized cavities (i.e. cerebrospinal fluid, fluid in GI tract, intraocular, etc)
1/3 of body water is located here
1 Liter of water weighs
2.2lbs (1kg)
How many mL's are in 8oz?
240mL
(True/False)
The electrolyte composition varies between ECF and ICF but the overall concentration of electrolytes is the same in the two compartments.
True
(the concentrations of specific ions differ greatly)
Main cation and anion in ECF
sodium(Na+)
chloride(Cl-)
main cation and anion in ICF
potassium(K+)
phosphate(PO43-)
movement of molecules from an area of high concentration to one of low concentration is called...
diffusion
when molecules combine with specific carrier molecules and speeds up the rate of diffusion
ex. glucose transport
facilitated diffusion
process in which molecules move against the concentration gradient
external energy (ATP) is required
sodium moves out of the cell and potassium move into the cell to maintain the concentration difference using this mechanism (sodium-potassium pump)
active transport
Osmosis
movement of water btwn 2 compartments separated by a semipermeable membrane
water moves thru the membrane from dilute to more concentrated
no outside energy required
Osmotic pressure
amount of pressure required to stop the osmotic flow of water (to stop the water from going to the more concentrated area)
determined by the concentration of solutes in solution
Osmolality
indicates the water balance of the body
PLASMA osmolality- 275-295mOsm/kg
>295 indicates concentration is too great or water content is too little and is called
"water deficit"-hypovolemia
<275 indicates concentration is too low or water content is too high and is called
"water excess"-hypervolemia
fluids with the same osmolality as the cell interior
isotonic
fluids in which the solutes are less concentrated than the cells
hypotonic
if a cell is surrounded by hypotonic fluid, water moves into the cell, causing it to swell
fluids in which the solutes are more concentrated than cells
hypertonic
if a cell is surrounded by hypertonic fluid, water leaves the cell to dilute the ECF and the cell shrinks
Hydrostatic pressure
the force within a fluid compartment
the major force that pushes water out of the vascular system at the capillary level
Oncotic pressure
normal- 25 mm Hg
osmotic pressure exerted by colloids in solution
major colloid in vascular system contributing to total osmotic pressure is protein. protein attracts water pulling fluid from tissue space to vascular space
capillary hydrostatic pressure and interstitial oncotic pressure moves water...
OUT of the capillaries
plasma oncotic pressure and interstitial hydrostatic pressure moves water ...
INTO the capillaries
edema
fluid accumulation in the interstitium
caused by increase in venous hydrostatic pressure <-- caused by fluid overload, heart failure, liver failure, obstruction of venous return to the heart
First spacing
normal distribution of fluid in the ICF and ECF compartments
second spacing
abnormal accumulation of interstitial fluid (i.e. edema)
third spacing
when fluid accumulates in a portion of the body (transcellular fluid) from which it is not easily exchanged with the rest of the ECF
the fluid is trapped and unavailable for functional use
(i.e. ascites, edema associated with burns)
hypothalamus
controls thirst response and ADH release from pituitary
if water deficit- stimulation of thirst response and ADH release
if water excess- suspression of both resulting in urinary excretion of water
ADH (antidiuretic hormone)
regulates WATER retention by the kidneys
factors that stimulate ADH release: stress, nausea, nicotine, and morphine
SIADH- causes water retention
reduction of ADH release- causes diabetes insipidus: copious amounts of dilute urine excreted bc water isnt reabsorbed appropriately, excessive thirst, dehydration, hypernatremia
glucocorticoids ans mineralocorticoids
regulate both water and electrolytes
cortisol
most abundant glucocorticoid
antiinflammatory effect
increase serum glucose levels
aldosterone
mineralocorticoid
sodium retention
potassium excretion
kidneys
primary organ for regulating fluid and electrolyte balance
produces ~1.5L of urine/day
impaired renal function results in: edema, potassium and phosphorus retention, acidosis
Cardiac regulation
peptide hormones are produced that act on renal tubules to promote excretion of sodium and water, resulting in decrease in blood volume and BP
normal daily intake and output
2000-3000mL
invisible vaporization from lungs and skin helping to regulate body temp
insensible water loss: increases by exercise and increased body temp
Gerontologic considerations
structural changes and decrease in renal blood flow
decrease in aldosterone
increase in ADH
increase loss of moisture thru skin-inability to respond to heat/cold changes
decreased thirst mechanism
musculoskeletal changes effect ability to get/hold onto fluids or use restroom
mental status changes
incontinent episodes
fluid volume deficit (hypovolemia)
causes: diarrhea, fistula drainage, hemorrhage, polyuria, inadequate intake, shift of fluid from plasma into interstitial fluid
Tx: correct underlying cause and replace both water and any needed electrolytes, lactated ringers, isotonic (0.9%) sodium chloride for rapid replacement, or blood
dehydration
loss of pure water alone without corresponding loss of sodium
fluid volume excess (hypervolemia)
causes: excess intake of fluids, abnormal retention- heart/kidney failure, shift of fluid from interstitial fliud into plasma fluid
Tx: treat cause, remove fliud w/o producing abnormal changes in electrolyte composition or osmolality of ECF, *diuretics and fluid restrictions, may have to restrict sodium intake, paracentesis
Nursing implementation for fluid deficit
daily weights - 1lb (2.2kg) = 1Liter
I&Os - output should be at least 30mL
specific gravity (1.010-1.025): high-indicates concentrated urine
cardiovascular monitoring:
increased HR and vasoconstriction to make up for the less volume and keep the BP normal, orthostatic hypotension, if severe- weak, thready pulse
respiratory:
increased RR due to decreased tissue perfussion and resultant hypoxia
Neurologic:
altered sensorium bc of reduced cerbral tissue perfusion PEARRLA
LOC
voluntary muscle movement
muscle strength
reflexes
skin:
decreased skin turgor
cool and moist - vasoconstriction compensation
dry and wrinkled
dry mucous membranes
furrowed tongue
thirsty
Nursing implementation for fluid excess
daily weights - 1lb (2.2kg) = 1 Liter
I&Os - output should be at least 30mL
specific gravity (1.010-1.025): low-indicates dilute urine
cardiovascular:
full and bounding pulse
JVD
increased BP
respiratory:
pulmonary congestion/edema
SOB
irritative cough
moist crackles
neurologic:
cerebral edema
PEARRLA
LOC
voluntary muscle movement
muscle strength
reflexes
skin:
edema - cool skin bc fluid
hard/taut
Sodium (Na+)
135-145
main cation of EFC
sodium - absorbed in GI tract
role of sodium
maintains concentration and volume of ECF
generates/transmits nerve impulses
regulates acid-base balance
leaves trough urine, sweat, feces
kidneys role regarding sodium
primary regulator of sodium balance
regulate ECF concentration by excreting or retaining water under the influence of ADH
*aldosterone: key role in sodium regulation by promoting sodium reabsorption
hypernatremia
Na+ > 145
sodium gain or water loss
shifts water out of cell causing cellular dehydration/shrinkage
body's protection: thirst
caused by: altered LOC or inability to obtain fluids, ADH deficiency (i.e. diabetes insipidus) can result in diuresis, hyperosmolar tube feedings, hyperglycemia, excessive sweating, high fever
interventions: treat underlying cause, 5%D in H2O or hypotonic fluids, *reduce sodium levels slowly to avoid cerebral edema, administer diuretics, dietary sodium restrictions, daily weights
hyponatremia
Na+ < 135
sodium loss or water gain
shifts water into cell causing cellular swelling
caused by: inappropriate hypotonic fluid therapy, SIADH - abnormal retention of water, losses thru GI tract, kidney, or skinactivation of thirst and ADH
manifestations: increased cellular excitability, dysrhythmias, cardiac standstill, leg cramps, weakness/paralysis of skeletal muscles, abdominal cramping, diarrhea
interventions: eliminate potassium intake, increase potassium elimination (diuretics, increased fluid intake), force from ECF to ICF *using insulin or sodium bicarbonate, administer calcium gluconate, *ECG monitoring
role of potassium
major factor of neuromuscular and cardiac function
cellular growth
acid-base balance
inverse relationship btwn Na+ and K+ - factors that cause sodium retention cause potassium loss in urine; "whatever sodium wants to do potassium does opposite"
sources: diet- fruits, dried fruits, vegetables
role of kidneys regarding potassium
primary route of potassium loss (90%), rest thru sweat and stool
hypokalemia
K+< 3.5
caused by: abnormal losses from GI tract or kidneys, diuresis and elevated aldosterone (causes sodium retention and potassium loss), magnesium deficit, diarrhea, laxitive abuse, vomiting, ileostomy drainage, alkalosis shifts potassium ICF
manifestations: reduced cellular excitability, ventricular dysrythmias, weakness/paralysis of skeletal muscles, shallow respirations and resp arrest, hyporeflexia
interventions: potassium chloride supplements, increase dietary intake, *only give KCl if urine output of at least 0.5mL/kg/hr, **never give KCl via IV push, max concentration= 40, rate of admin: 10-20mEq/hr, assess IV site Qhr
