Body Fluid Compartments

Question 1

What is volume contraction?

Answer 1

A decrease in ECF volume
Also called volume depletion
Causes decreased blood volume and decreased BP

Question 2

What is volume expansion?

Answer 2

An increase in ECF volume

Causes increased blood pressure and edema

Question 3

How are fluid shift disturbances categorized?

Answer 3

According to whether they involve an increase or decrease in ECF volume
According to whether they cause a change in body fluid osmolarity

Question 4

What does isosmotic mean?

Answer 4

No change in body fluid osmolarity

Question 5

What does hyperosmotic mean?

Answer 5

Body fluid osmolarity is increased

Question 6

What does hyposmotic mean?

Answer 6

Body fluid osmolarity is decreased

Question 7

What is the only fluid that can be acted on directly to control its volume and composition?

Answer 7

Plasma

Any control mechanism that operates on plasma in effect regulates the entire ECF

Question 8

What are non-electrolytes that dissolve in water?

Answer 8

Contain covalent bonds that prevent them from dissociating in solution and therefore have no electrical charge (e.g. glucose, lipids, urea)

Question 9

What are electrolytes?

Answer 9

Dissociate into ions (ionize) in water
Ex. Mg, Na, Cl, K
Have a greater ability to cause fluid shift

Question 10

Which ions are high in ECF?

Answer 10

HCO3, Na and Cl

Question 11

Which ions are high in the ICF?

Answer 11

K and phosphate anions

Question 12

Cellular proteins in ICF cannot leave what?

Answer 12

The cell

Question 13

ECF volume must be closely regulated to help maintain what?

Answer 13

BP

Maintaining salt balance is of primary importance in the long term regulation of ECF volume

Question 14

ECF osmolarity must be closely regulated to prevent what?

Answer 14

Swelling or shrinking of cells

Maintaining water balance is of primary importance in regulating ECF osmolarity

Question 15

All body fluid compartments have approximately the same what?

Answer 15

Osmolality

Question 16

What is the tonicity of a solution?

Answer 16

The effect the solution has on cell volume—whether the cell remains the same size, swells or shrinks—when the solution surrounds the cell

Question 17

If cells are placed in an isotonic solution what will happen?

Answer 17

There will be equal movement of water in and out of the cell

Question 18

If cells are placed in a hypertonic solution what will happen?

Answer 18

There will be a net movement of water out of the cell which will cause the cell to shrink

Question 19

What will happen if cells are placed in a hypotonic solution?

Answer 19

There will be a net movement of water into the cell which will cause the cell to swell

Question 20

What are the main solutes in the ECF?

Answer 20

Na, glucose and urea

Question 21

What are the hormonal mechanisms to balance fluid compartments?

Answer 21

Renal sympathetic nerves
RAAS
ADH
Natriuretic peptide secretion

Question 22

ADH is secreted in response to what?

Answer 22

Angiotensin II
Atrial receptors in presences of low preload
Increased osmolality of blood
Sympathetic nervous system activation

Question 23

What does secretion of ANP induce?

Answer 23

Arteriolar dilation (decreases TPR)
Increases fluid loss (decreases preload) 
Inhibits renin (decreases both TPR and preload)

Question 24

What is the main action of ANP?

Answer 24

To directly inhibit Na reabsorption in the distal parts of the nephron thus increasing Na excretion and accompanying osmotic water excretion in the urine

Question 25

What are the other actions of ANP?

Answer 25

Inhibits renin, aldosterone and ADH secretion

Question 26

What are the two forms of dehydration?

Answer 26

Hypernatremic and hyponatremic dehydration

Question 27

Describe hypotonic (hyponatremic) dehydration

Answer 27

Loss of Na is greater than loss of water in ECF Serum Na concentration in the ICF is greater than that of the ECF Water shifts from the ECF to the ICF to establish osmotic equilibrium Serum Na and serum osmolality will be less than the normal range

Question 28

Describe hypertonic (hypernatremic) dehydration

Answer 28

Loss of water is greater than the loss of Na in ECF Serum Na concentration in the ECF is greater than in the ICF Water shifts from ICF to ECF Serum osmolality will exceed 300 mOsm/kg Serum Na will be more than 150 mEq/L

Question 29

Describe hyponatremia

Answer 29

Serum Na level below 130-135 mEq/L Na deficit decreases the ECF osmotic pressure and water moves into the cells Water movement causes sx related to hypovolemia and cellular swelling

Question 30

What are the results of hyponatremia?

Answer 30

Increased ICF causes edema, brain cell swelling, irritability, depression, confusion, weakness, muscle cramps, anorexia, nausea and diarrhea Pure Na deficits cause hypotension, tachycardia, and decreased urine output

Question 31

Describe hypernatremia

Answer 31

Serum Na levels above 147-150 mEq/L | Water moves from ICF to ECF causing intracellular dehydration including shrinkage of brain cells but there is excess ECF

Question 32

What are the results of hypernatremia?

Answer 32

Increased ECF causes edema and increased BP High Na level causes muscular weakness and hyperactive reflexes Decreased ICF causes thirst, decreased urine output, confusion and ultimately coma

Question 33

Darrow Yannet diagrams are used to study the effect of what?

Answer 33

Various clinical conditions such as dehydration, shock, vomiting, and diarrhea on osmolality and volume of ECF and ICF

Question 34

What changes occur during dehydration (hyperosmotic volume contraction)?

Answer 34

Hypotonic fluid loss conditions like dehydration, diabetes insipidus, and alcoholism Insensible water loss from ECF, solute is left behind and becomes concentrated Decrease in ECF and ICF but an increase in body osmolality

Question 35

What is diabetes insipidus?

Answer 35

Body is either unable to produce ADH or kidneys cannot respond to it leading to a hyperosmotic volume contraction There is a decrease in free water reabsorption from the distal tubules leading to free water loss

Question 36

What is diabetes mellitus?

Answer 36

Body does not produce insulin High levels of glucose in blood Osm will be 330 in DKA

Question 37

What are the 4 mechanisms that can cause polyuria?

Answer 37

Increased intake of fluids as in psychogenic causes, stress and anxiety Increased GFR as in hyperthyroidism, fever and hypermetabolic states Increased output of solutes occurs in DM, HTN, hyperparathyroidism, use of diuretics Inability of the kidney to reabsorb water in DCT as in CDI, NDI, drugs and chronic renal failure

Question 38

What is water diuresis?

Answer 38

Increased water excretion without corresponding increase in salt excretion Primary cause is increased intake of water due to polydipsia or diabetes insipidus

Question 39

What is solute (osmotic) diuresis?

Answer 39

Increased water excretion concurrent with increased salt excretion Primary cause is significant increase in salt present in tubular fluid Hyperglycemia, high protein intake, recovery from AKI

Question 40

What changes occur with adrenal insufficiency (hyposmotic volume contraction)?

Answer 40

ICF volume increase, ECF volume and osmolarity decrease Adrenal insufficiency due to loss of aldosterone leading to excessive loss of NaCl in urine Transient response is that ECF osmolarity decreases and fluid shifts to ICF until osmolarity equilibrates

Question 41

What changes occur during SIADH (hyposmotic volume contraction)?

Answer 41

Gain of hypotonic fluid Conditions like excess water drinking and SIADH (syndrome of inappropriate ADH) Increase in ECF and ICF volume but a decrease in body osmolality

Question 42

What changes occur with isosmotic volume contraction?

Answer 42

Acute fluid loss conditions like hemorrhage, diarrhea and vomiting Diarrhea causes loss of isosmotic fluid from the GI tract Decrease in ECF volume and no change in body osmolality or ICF volume

Question 43

What changes occur with isosmotic volume expansion?

Answer 43

ECF volume expands, ICF and osmolality don’t change | Isotonic saline injection of NaCl

Question 44

What changes occur with hypertonic volume expansion?

Answer 44

ECF volume increases, ICF volume decreases, osmolality increases Transiently ECF osmolarity increases so volume shifts from ICF to ECF until osmolarity equilibrates High NaCl intake or infusion of hypertonic solution (ex. 2-3% NaCl)