Fluid Imbalances Week 2 Flashcards
(32 cards)
What are ways to gain water?
Loss water?
Give average calues
Gains
- Water intake- 1200
- Intake from food- 1000
3 Oxidation of water- 300
Total gains 2500 ml/Day
Losse-
1 Urine- 1500 ml
- Feces- 200
- Skin 350
- Lungs 350
Total 2500 ml?day
Give examples of fluid imbalacnes.
What are some affects of these imbalances?
IV injections
o isotonic saline
o hypertonic saline
o lactated Ringer’s solution
o D5W (5% dextrose in water)
- drinking water
- vomiting
- diarrhea
- sweating
imbalance affects 1. Acid/base 2. Electrolytes– mainly Na+ (because Na is most abundant and imperable) and K+ (because K+ is tightly maintained)
What is more common hyperkalemia or hypokalemia?
HYPOKALEMIA
Hypokalemia is the most common problem due to K+ loss in fluids. Hyperkalemia is rarely seen in normal persons because of rapid K+ uptake into cells and rapid renal excretion. Hypokalemia leads to widespread functional changes.
What causes water to move
Osmotic graadients between fluid compartments
Explain total body water.
Why are there variations?
Average percent in adult male and female?
total body water (TBW) = the sum of the water content of all of the body fluids.
Greatest at birth (up to 83%) and declines after birth
Adult females TBW = 45–50% of body weight
males TBW = 55–60% of body weight (use 60%)
TBW is a constant percentage of lean body mass (LBM), i.e. the fat-free part of body, because the water content of specific tissues is relatively constant and individual organs and tissues are a
relatively constant fraction of body mass.
Fat takes 10% of its weight in water, but since the amount of fat varies there can be large differences in %TBW of total BW
Organs and there average water weight percentage
ORGAN/TISSUE WATER
blood, kidney 80 to 84
muscle, heart, lungs, skin, brain 75 to 79
intestines 70 to 74
liver 65 to 69
bone 22
fat 10
(% of organ weight)
What is the generaly ditribution of TBW between intracellylar and extracellular
60% intracellular
40% Etracellular (plasma 7%, INtersitital fluid/lymph 31%, Transcellular fluid 1-2%)
But remember The barriers between ECF and ICF are the plasma membranes of cells that are highly permeable
to water.
Equation for concentration of TBW, ECF, and ICF
HOw do we measure this?
Cocntration= Quatity/Volume
We measure this by administering a known quatity of Q of an indicator (tracer), wait for equilibrium and measure concentration of the indicator. Then calculate volume.
When measuring volume, what are important characeteristics of the tracer?
Tracer characteristics:
• non-toxic
• only distributes in volume of interest
• distributes evenly
• distributes rapidly
• does not alter existing fluid distribution
• is measurable
How do we measure ICF
Measurements of ICF volume are extremely difficult to make directly because of the properties of the cell membrane. Consequently measurements of TBW and ECF volumes are made and ICF volume is then obtained by subtraction.
What are tracers used for TBW, ECF, Plasma, and BLood volume
Total body water— (TBW) D2O, urea, antipyrine
extracellular fluid—- inulin, radioactive Na, Cl, SO4
plasma— T-1824, radioactive iodinated serum albumin (RISA)
blood volume RISA plus Cr-RBC
useful equations for finding ICF and ISF
ICF volume = TBW – ECF
ISF + lymph volume = ECF – plasma volume
Why can’t we sustain osmotic oncentraiton diffrence in ICF and ECF
BEcause plasma membrances are freely permeable to water
How dowe establish osmotic concentration differnce Between ICF and ECF
With cell-imperable solutes like Na+. Na+ is effectively cell-impermeable because any Na+ that moves into the cells is
pumped out again. Changes in the [Na+]ECF causes an ECF/ICF water exchange
What happens if we add Na+ to plamsa with water
- The plasma is hypertonic to ICF
2 Since Na+ can’t move water leaves the cells and goes to the ECF
- This shirnks the ICF volume and increase ECF volume and contiunes until we reach equilibtiu,
HOw do we find plasma concentration? Why is this useful?
Plasma [Na] is a good index of the osmolar concentration of the body fluids b/c:
• Na+ (with its associated anions) is the largest component of the plasma solute (>90%
• the concentration of other plasma ions is small and may be assumed to be constant
• the concentration of water in plasma is usually constant, so changes in [Na+]p reflect changes in the osmolar concentration of body water
2 x {Na} + 10mOsml/L = plasma osmolar concentation
Useful b/c- all body fluids have the same osmolar concentration. Therefore, one can estimate osmolar concentration of body fluids by measuring the osmolarity of the plasma.
The equation 2x Na + 10oSm/L works for plasma osmolar, but what do we consider in diabetes
Other solutes may be present in abnormally high concentration.
like glucose in diabetes mellitus. Normally glcuose osmolarity is 100 mg/dl and it is account for in the additional 10mosm/L, but when abnormal we do the below to include the excess glcuose.
Divide glucose by it MW (180) to convert mg/dl to mmol/dl.
Then multiple by 10 to convert mmol/dL to mmol/L
10 (glucoseplasma- glucose normal)/ 180
What happens when adding D5 through IV?
1 .The fluid distributes to ECF diluting imperable solutes (mainly Na+)
- Creates osmotic gradient so water flows into cells until graident is fone.
Final outcome- equal dilution of all compartmetns- remember the glucose will trigger endorcinre response uptaking flucose and once glucose is gone there is no net osmotic effect.
What happens when we give 1 L of isomotic NaCL
- Cells are mainly imperamable to Na+ so it will remin in the EFC along with Cl-
- Since isomotic solution was added the water stays in the EFC as well and the ECF expands isomotically
What happens when you give 1 L hyperosmotic saline through an IV
- NaCL can’t enter the cell so it stays in the ECF
- Water leaves the cells into the plasma because of the osmotic gradient
FInal outcome- ECF increases in volume and volume of IC decrease. The osmolar concentration of all compartments increases.
R
What does changing the concentration of one compartment do to the other compartments of the body
emember Changing the concentration of
one body compartment changes the concentration of all compartments.
Example- giving 1 L of hyperosmotic NaCl
Clinical consequences of excess isotonic salt and water
Expands ECF (like in cardiac, renal and endocrine disorders) results in resp and CV changes- elevated plasma volume signs= edema, SOB
Clnical consequences of isotonic salt water loss
Decrease in ECF volume– like diahearra, sweating, exudation from butsn or there may be a large trasfer to transcellular compartns (ascites) or to ISF (trauma) which are equivalant to losing ECF.
SIgns- reduced tissue perfusion. Rapid changes may result in changes to hemotocrit and plasma protein.
Clinical ocnsequences of water defecit
Increase in concentratio of from excess loss relative to solute or solute gain excess to water
Signs- neurological- restlnessness irritability, spasms, seizures
