EXAM 2 - FLUIDS Flashcards
How much of total body weight is body water?
60%
decreases with age and % of body fat
Functions of body fluids
lubricant
metabolism - solvent for chem. reactions
transport of O2, nutrients, chemical messengers
regulates body temperature
How much of total body water is extracellular fluid?
33%
How much of total body water is intracellular fluid?
66%
How much of extracellular fluid is interstitial fluid?
25%
How much of extracellular fluid is blood plasma?
8%
What is osmolality?
solute concentration in the blood/fluid
What is osmosis?
water movement across a semi-permeable membrane from lower concentration to higher concentration
sodium, a solute, is main ion
What is diffusion?
movement of particles down a concentration gradient
What is active transport?
movement of particles against a concentration gradient, requires energy
What is hydrostatic pressure?
water ‘pushing’ pressure
What is osmotic pressure?
water ‘pulling’ pressure
What is colloidal osmotic pressure (COP)?
albumin - a protein, is the main colloid
large plasma protein that influences water movement
water ‘pulling’ pressure
What is filtration?
fluid exits capillary since capillary hydrostatic pressure is greater than blood colloidal osmotic pressure
What is no net movement?
capillary hydrostatic pressure = blood colloidal osmotic pressure
What is reabsorption?
fluid re-enters capillary since capillary hydrostatic pressure is less than blood colloidal osmotic pressure
What contributes to water gain?
food and drink, metabolism
What contributes to water loss?
skin, lungs, urine, feces
What contributes to insensible water loss?
skin and lungs
How does the body tell us we need more intake? (for balance)
increase osmolality
decrease circulating volume
dry mucous membranes
aldosterone
antidiuretic hormone (ADH)
How does the body increase output? (for balance)
natriuretic peptides
BNP - brain
ANP - atrial
How does aldosterone help us increase fluids?
secreted by adrenal cortex
renal tubules reabsorb Na and H2O
(water follows sodium)
excretes K+
How does ADH help us increase fluids?
synthesized in hypothalamus
stored and released from posterior pituitary
released with increase osmolality and decreased circulating volume
effects distal tubule and collecting ducts for water reabsorption, decreased urine, increased concentration of urine
How does ANP and BNP help us decrease fluids?
ANP is released from R atrium when heart is stretched - increased circulating volume
BOTH promote fluid excretion
increased Na+ excretion which takes H2O
DIURESIS
What is diuresis?
increased production of urine by the kidneys
What can increase diuresis?
caffeine, exercise, increased fluid intake, alcohol, medications
What are the 4 types of diuretics?
Loop - furosemide
Thiazide - hydrochlorothiazide
Potassium sparing - spirnolactone
osmotic - mannitol
What is tonicity?
the osmotic pressure of a solution and how much it influences the movement of water
isotonic solution
concentration of stuff equal to intravascular plasma
0.9% saline, lactated ringers, D5W
hypotonic solution
concentration of stuff less than plasma, fluid would move out of the vascular space
0.45% saline
hypertonic solution
concentration of stuff more than plasma, fluid would move into the vascular space
3% saline, D5W+0.9% saline
What are the two major categories of fluid imbalances?
- imbalance of volume, too much or too little
- imbalance of concentration, too many or too few
What is a volume deficit called?
hypovolemia
What is isotonic hypovolemia?
equal decreased water and Na+, too much out, too little in
What are the causes of isotonic hypovolemia?
emesis or gastric drainage, diarrhea, burns, hemorrhage, excessive perspiration
What causes intravascular hypovolemia?
third spacing - edema or ascites
What are some clinical manifestations of hypovolemia?
increased HR, postural hypotension, weight loss, flat neck veins, prolonged cap refill, lightheadedness, oliguria, decreased skin turgor, dry mucous membranes, hard stools, soft, sunken eyeballs, longitudinal furrows in tongue, absence of tears/sweat, sunken fontanel in infants
What causes hypervolemia?
excessive infusion of isotonic solution, renal retention of Na and H2O, CHF, cirrhosis, chronic renal failure, increased intake
What are some clinical manifestations of hypervolemia?
weight gain, edema, bounding pules, distended jugular vein, crackles, orthopnea, bulging fontanel
What are the causes of edema?
- increased capillary hydrostatic pressure
- increased interstitial osmotic pressure
- decreased capillary osmotic pressure
- blockage of lymph drainage (cancer, infection, removed lymph nodes)
What can cause increased capillary hydrostatic pressure?
increased blood pressure, vein blockage
What can cause increased interstitial osmotic pressure?
increased vascular permeability, leakage of protein into interstitial space which increases the osmotic pressure & contributes to more fluid being lost from inside vessels
What can cause decreased capillary osmotic pressure?
decreased plasma proteins/albumin, or loss of plasma proteins causing increased capillary permeability
Why would a blockage of lymph drainage cause edema?
the lymphatic circulation carries excess interstitial fluid and protein back to the systemic circulation, it also has a lot of lymphocytes
How is increased hydrostatic pressure edema?
interstitial space is elastic and expandable, excess fluid in the interstitial space is edema, there can be a significant increase in ECF BEFORE you see edema
How much does 1L of fluid weigh?
1 kg (2.2 lbs)
What kind of venous obstructions can cause edema?
thrombophlebitis, hepatic obstruction, tight clothing on extremities, prolonged standing
What can Na and H2O retention cause?
CHF and renal failure
What is third spacing?
shift of fluid from intravascular space to a space where it can’t be used, usually a serous cavity
pleural, pericardial, peritoneal
protein-rich fluid pulls water into space
What are some problems with fluid accumulation and edema?
increased distance for diffusion of nutrients/O2, impaired blood flow, slowed healing, increased risk of infection, pressure sores over bony prominences
MOA of loop diuretics
work in loop of Henle to decrease absorption of NA, CL, K, and Ca
osmotic gradient, prevents reabsorption of water
side effects of loop diuretics
N/V, constipation, diarrhea, hypokalemia, dehydration, tinnitus and hearing impairment
