Fluid Imbalances Week 2

Question 1

What are ways to gain water?

Loss water?

Give average calues

Answer 1

Gains

1. Water intake- 1200
2. Intake from food- 1000

3 Oxidation of water- 300

Total gains 2500 ml/Day

Losse-

1 Urine- 1500 ml

2. Feces- 200
3. Skin 350
4. Lungs 350

Total 2500 ml?day

Question 2

Give examples of fluid imbalacnes.

What are some affects of these imbalances?

Answer 2

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)

Question 3

What is more common hyperkalemia or hypokalemia?

Answer 3

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.

Question 4

What causes water to move

Answer 4

Osmotic graadients between fluid compartments

Question 5

Explain total body water.

Why are there variations?

Average percent in adult male and female?

Answer 5

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

Question 6

Organs and there average water weight percentage

Answer 6

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)

Question 7

What is the generaly ditribution of TBW between intracellylar and extracellular

Answer 7

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.

Question 8

Equation for concentration of TBW, ECF, and ICF

HOw do we measure this?

Answer 8

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.

Question 9

When measuring volume, what are important characeteristics of the tracer?

Answer 9

Tracer characteristics:
• non-toxic
• only distributes in volume of interest
• distributes evenly
• distributes rapidly
• does not alter existing fluid distribution
• is measurable

Question 10

How do we measure ICF

Answer 10

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.

Question 11

What are tracers used for TBW, ECF, Plasma, and BLood volume

Answer 11

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

Question 12

useful equations for finding ICF and ISF

Answer 12

ICF volume = TBW – ECF

ISF + lymph volume = ECF – plasma volume

Question 13

Why can’t we sustain osmotic oncentraiton diffrence in ICF and ECF

Answer 13

BEcause plasma membrances are freely permeable to water

Question 14

How dowe establish osmotic concentration differnce Between ICF and ECF

Answer 14

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

Question 15

What happens if we add Na+ to plamsa with water

Answer 15

1. The plasma is hypertonic to ICF

2 Since Na+ can’t move water leaves the cells and goes to the ECF

3. This shirnks the ICF volume and increase ECF volume and contiunes until we reach equilibtiu,

Question 16

HOw do we find plasma concentration? Why is this useful?

Answer 16

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.

Question 17

The equation 2x Na + 10oSm/L works for plasma osmolar, but what do we consider in diabetes

Answer 17

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

Question 18

What happens when adding D5 through IV?

Answer 18

1 .The fluid distributes to ECF diluting imperable solutes (mainly Na+)

2. 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.

Question 19

What happens when we give 1 L of isomotic NaCL

Answer 19

1. Cells are mainly imperamable to Na+ so it will remin in the EFC along with Cl-
2. Since isomotic solution was added the water stays in the EFC as well and the ECF expands isomotically

Question 20

What happens when you give 1 L hyperosmotic saline through an IV

Answer 20

1. NaCL can’t enter the cell so it stays in the ECF
2. 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.

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Question 21

What does changing the concentration of one compartment do to the other compartments of the body

Answer 21

emember Changing the concentration of
one body compartment changes the concentration of all compartments.

Example- giving 1 L of hyperosmotic NaCl

Question 22

Clinical consequences of excess isotonic salt and water

Answer 22

Expands ECF (like in cardiac, renal and endocrine disorders) results in resp and CV changes- elevated plasma volume signs= edema, SOB

Question 23

Clnical consequences of isotonic salt water loss

Answer 23

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.

Question 24

Clinical ocnsequences of water defecit

Answer 24

Increase in concentratio of from excess loss relative to solute or solute gain excess to water

Signs- neurological- restlnessness irritability, spasms, seizures

Question 25

Clinical consequences of water excess

Answer 25

Diluteion of body fluids due to 1. excess water intake 2 excess renal water retention 3. Sweating or Gi losses followed by water only replacemnt. THis expands all compartmetns and can be extremely dangerous in CNS because the cranium is closed.

Signs and symptoms are mainly neurological: confusion, disorientation, twitching, seizures,
coma, death.

Question 26

what cells are mintaly affected by water loss or excess

Answer 26

As [Na+]p changes, an osmolar gradient is created between the blood/brain barrier, causing brain cells to taken water (increase in size) or
release water (shrink in size).
Rapid change in cranial ICF volume can seriously affect CNS function:
• Rapid volume increase compresses cranial blood vessels and reduces blood flow.
• Rapid volume decrease pulls the cranial mass away from the meninges and can tear blood vessels that bridge the space between the meninges and the brain, causing hemorrhage
and loss of perfusion.

Slow changes in cranial ICF volume are much less serious because CNS cells have volume
regulating mechanisms:
• Slow reduction in ECF osmolarity causes brain cells to extrude electrolytes, thereby reducing the intracellular osmolarity.
• Slow increase in ECF osmolarity causes brain cells to accumulate proteins that counterbalance the elevated extracellular concentration.

can be treated by 1. Mannitol 2. Large amounts of hypo or hypertoni IV slowly

Question 27

Clnical consequences of Fluid Loss

Answer 27

When body fluids are lost during sweating, vomiting, or diarrhea, the clinical consequences are more than just because of osmotic changes. All fluid loss results in water loss, but other consequences occur because the ionic composition of these fluids is very different

When loss from ICF, it is gernally replaced by ECF which can lead to osmotic shifts of water (because of Na+) or hypokalemia due to loss of K+ or metabolic acidosis/alkalsos due to lsos of H+ or bicarb

Question 28

What are the electrolyte composittions of Sweat, gastric juice, bile, pancreatic juice, illeal fluid, cecal fluid

Answer 28

Na+ K+ Cl- HCO3-

Sweat 45 5 58 0
Gastric juice 60 9 84 0
Bile 149 5 101 45
Pancreatic juice 141 5 77 92
Ileal fluid 129 11 116 29
Cecal fluid 80 21 48 22

Question 29

IS sweating hyper or hypotonic?

GI secretions?

Answer 29

Hypotonic so water moves from ICF to ECF

GI secretions are isomotic- loss doesn’t alter body fluid concentration

Question 30

Properities of sweat vomit and diarrhea

Osmolarity? pH? and K+?

Answer 30

• *Fluid osmolarity pH K+**
• *sweat** hypotonic neutral (7.4) ≥ ECF
• *vomitus** isotonic acidic high
• *diarrhea** isotonic alkalotic high

Question 31

What is insensible water loss?

What are the sources?

Answer 31

Pure water is continuously lost from the body through the evaporative water loss from body surfaces.– NOT SWEAT!

1. Skin- water diffuses through cutaneous layers and depends on skin tmep, relative humidity. It increase in fever and hot and dry and in burns.
2. Respiratory mucusoa- inspired air is cooler than body temp and has a humidity of less than 100% while expired air is fully saturated so expired ait has .034 mL water/L

Question 32

Explain obligatory water loss

Answer 32

Lastly, recall that even with maximal ADH secretion, the urinary solute excretion does not stop. It is contained in the smallest possible volume of urine at the highest possible concentration, but still contains water. This volume is called obligatory urine volume. It is about 600–800 ml/day.