Chapter 17 Fluids: Med Surg Flashcards
what does water content vary with?
gender, age, body mass
percentage of body weight of water greater in men or women?
men
who would have more water content as compared to body weight?
infants 70%-80%
intracellular fluid
2/3 of body water and 40% of body weight
extracellular fluid
1/3 of body water, consisits of intravascular, interstitial and transcellular spaces
intravascular space
1/3 of ECF located here as plasma
interstitial space
2/3 of ECF
transcellular space
1 L of ECF; CSF, fluid in GI, pleural, synovial, peritoneal fluid
why is body water needed?
fluids are in constant motion and transport nutrients, electrolyes, oxygen, regulate temperatures, lubricate joints and membranes, and aids digestion
how much does 1 L of fluid weigh?
2.2 kg
electrolytes
molecules dissociate (split into ions) when placed in water
ions
electrically charged particles
cations
positive charged ions
anions
negative charged ions
valence
electrical charge of an ion
ECF cation
sodium
ECF anion
chloride
ICF cation
potassium
ICF anion
phosphate
diffusion
movement of molecules from an area of high concentration to one of low concentration; membrane must be permeable; no energy
facilitated diffusion
same as diffusion, but some molecules diffuse slowly into the cell and need some help so a carrier molecule accelerates the rate; no energy
active transport
molecules move against the concentration gradient, external energy is required; e.g. sodium potassium pump: potassium in and sodium out
osmosis
water movement through a semipermeable (favors water not solutes) membrance from an area of low solute concentration to an area of high solute concentration; no external energy, stops when equal
osmolality
describes fluids (water balance) inside the body, typically performed to evaluate the concentration of plasma in urine
normal plasma osmolality
275-295
increased plasma osmolality
concentration is too high or water is too low aka water deficit -> dehydrated
decreased plasma osmolality
concentration is too low or water is too high aka water excess
major determinant of plasma osmolality
sodium and glucose
ECF and ICF are:
isotonic to each other, hence no movement of water occurs and no gain or loss of water occurs although ECF expands e.g. lactated ringers, 0.5% saline
if the cell is surrounded by hypotonic fluid:
water moves into the cell and causes it to swell and possibly burst ECF -> ICF e.g. 0.45% saline
if the cell is surrounded by hypertonic fluid:
water leaves the cell to dilute the ECF and the cell shrinks and may eventually die ICF -> ECF e.g. 3% saline
hydrostatic pressure
force within the fluid compartment, blood pressure generated by the contaction of the heart and pushes water out of the vascular system
oncotic pressure
osmotic pressure exerted by colloids in solution, pulls fluid from the tissue space to the vascular space
major colloid
protein, which does not dissolve completely since they are too large of molecules
what two pressures move water into the capillaries?
plasma oncotic pressure and interstitial hydrostatic pressure
what two pressures move water out of the capillaries?
capillary hydrostatic pressure and interstitial oncotic pressure
first spacing
normal distribution of fluid in ECF and ICF
second spacing
abdnormal accumulation of interstitial fluid (edema)
third spacing
fluid accumulates in a portion of the body (transcellular fluid) from which it is not easily exchanged with the rest of the ECF, not functional e.g. ascites, edema with burn, trauma
how does the hypothalamus, pituitary, and adrenal cortex respond in water regulation?
the hypothalamus recognizes a fluid deficit and increases plasma osmolality sending osmoreceptors to the posterior pituitary and releasing ADH, which acts in the distal tubules to cause water reabsorption
decreased ADH
diabetes insipidus
increased ADH
SIADH
dextrose solutions
osmolarity changes once dextrose is metabolized
at the arterial end of the capillary:
capillary hydrostatic pressures exceeds plasma oncotic pressure, which draws fluid into interstitium (EDEMA)
at the venous end of the capillary:
capillary hydrostatic pressure is lower than plasma oncotic pressure and fluid is drawn back into the capillary
glucorticoids
cortisol, which has an antiinflammatory effect and increases glucose levels
mineralocorticoids
aldosterone, which enhances sodium retention and potassium excretion
primary organ that controls f&e balance
kidneys
insensible water loss
600-900 mL lost a day, ONLY water, sweating is sensible perspiration and causes f&e loss
how do you calculate fluid requirement for a pediatric patient?
convert weight to kg, 100 mL/kg for first 10 kg, 50 mL/kg for second 10 kg, and 20 mL/kg for the remainder of weight. IF ASKED FOR IN ML/HR SIMPLY DIVIDE ANSWER BY 24
fluid volume deficit
restless, drowsy, thirst, decreased skin turgot and capilarry refill, increased pulse, decreased urine, increased respirations, weight loss
fluid volume excess
headache, edema, venous distention, bounding pulse, increased blood pressure, dyspnea, crackles, muscle spasms, weight gain
assess neurologic fx
LOC, pupillary response to light and equality of size, voluntary movement of extremities, degree of muscle strength, reflexes
assess skin turgor where?
clavicle!
first signs of deficit:
tachycardia, decreased blood pressure, increased respirations
late signs of deficit:
hypotension and decreased capillary refill
