Fluids and Electrolytes

Question 1

Where is intracellular fluid and what is its purpose?

Answer 1

• within the cell

- responsible for oxygenation, nutrition, hormone transport, and waste removal

Question 2

Where is extracellular fluid and what is its purpose?

Answer 2

Responsible for maintaining blood volume and pressure
Three types: Interstitial - between cells and outside of blood vessels (see video)
Intravascular - the blood plasma, to carry oxygen, carbon dioxide, and nutrients to cells
Transcellular - lymph, synovial (in joints), intestinal, csf, sweat, urine, pleural, peritoneal, pericardial, ocular

Question 3

What proportion of fluid within the body is in each compartment?

Answer 3

Intracellular - 2/3 total body water (40%)
Extracellular - 1/3 total body water (20%)
Obesity - less water by percentage
Infants - more water percentage

Question 4

Explain how hydrostatic pressure and osmotic pressure control movement of fluids between the ICF and ECF

Answer 4

As the plasma flows from the arterial end of the capillary to the venous end of the capillary there are 4 forces that help determine if the fluid will move out of the capillary and into the interstitial space (filtration) or if the fluid moves back into the capillary space from the interstitial space (reabsorption)

Capillary hydrostatic pressure (blood pressure):
pushes water from capillary to interstitial space
1. At the arterial end of the capillary the hydrostatic pressure is higher than the oncotic pressure (fluid move into interstitial space)
2. At the venous end of the capillary, capillary oncotic pressure exceeds hydrostatic pressure so fluids are pulled back into vascular space (reabsorption)

Capillary oncotic pressure - pulls water from the interstitial space back into the capillary

Interstitial hydrostatic pressure - pushes water from the interstitial space into capillary and lymphatics

Interstitial osmotic pressure - pulls water between the interstitial space and intracellular space

Question 5

What assessment findings would you expect to see in patients who have decreased osmotic pressure due to low protein intake?

Answer 5

Low protein will cause fluid to leak from the capillary into the ECF. Protein attracts water and increases blood volume intravascularly. Therefore, they will display signs of edema (swelling, weight gain, and pitting)

Question 6

How does ADH affect water balance? How does aldosterone affect sodium balance?

Answer 6

ADH - antidiuretic hormone prevents loss of fluid, causes retention of water thus increasing volume

Aldosterone - retains sodium making solution hyperosmolar thus leading to water retention

Question 7

Define and give examples of each: localized edema, generalized edema, pitting edema, third spacing

Answer 7

localized edema: one area or organ, pulmonary edema, cerebral edema

generalized edema - more uniform in many areas (anasarca)

pitting edema - dent left after applying pressure

third spacing - fluid in body cavities; not available for metabolic purposes. Fluid flows from intravascular space into the interstitial or third space “nonfunctional space”

Question 8

What are several clinical manifestations of dehydration from isotonic hypovolemia?

Answer 8

Weight loss, dry skin, and mucous membranes decreased urine output, tachycardia, possible decreased BP - decreased perfusion

Question 9

What are some common causes of isotonic dehydration/hypovolemia?

Answer 9

Sweating, blood loss, wound drainage

Question 10

What would happen if you gave a patient with isotonic dehydration a hypertonic IV solution? Would the patient get better or worse?

Answer 10

Sodium would increase leading to a hyper-osmolar condition. Patient would get worse because water would be pulled from cells causing cellular shrinkage - elevated serum osmolality, tissue dehydration, polydispia, CNS changes (lethargy, hard to arouse)

Question 11

What are several clinical manifestations of isotonic hypervolemia?

Answer 11

weight gain, increased BP, SOB, increased urine output (if kidneys are functioning), decreased hematocrit (dilutional), JVD, HTN, edema

Question 12

What are some common causes of isotonic hypervolemia?

Answer 12

Too much IV fluid or sodium, chronic renal failure, heart failure, hyperaldosteronism (adrenal tumor) because kidneys retain too much sodium and water.

Question 13

Hyper-osmolarity

Answer 13

Etiology/Causes:
Decreased water intake
Increased loss of free water
Excess intake of hypertonic solutions

Pathophysiology:
Increased sodium causes water to be pulled out of cells
(cells shrink)

Elevated serum osmolatlity, tissue, dehydration, polydispia, CNS changes (lethargy, hard to arouse)

Question 14

Hypo-osmolarity

Answer 14

Etiology/Causes:
Excess water intake, Sodium deficit

Pathophysiology:
Decreased osmotic pressure of the ECF.
Water moves into the cell
Cell swell

Manifestations:
Decreased serum, osmolality,, decreased hematocrit (dilutional), CNS changes (confusion, headache)

Question 15

What is the relationship between the following?

Hyperkalemia and renal failure

Acidosis and hyperkalemia

Answer 15

-renal failure causes decreased excretion of potassium

-hyperkalemia and acidosis often occur together because H+ ions move into
the cell moving the potassium out of the cell

Question 16

Mr. Jones is admitted to the hospital with an exacerbation of heart failure. He had +3 peripheral edema of the lower extremities. Explain how this peripheral edema develops.

Answer 16

The underlying causes of edema include increased capillary hydrostatic pressure, lowered plasma oncotic pressure, increased capillary membrane permeability, and lymphatic channel obstruction. In a patient with heart failure, increased capillary hydrostatic pressure is the result of sodium and water retention and increased intravascular volume and likely reduction in plasma oncotic pressure secondary to hypoalbuminemia due to reduced protein intake and liver dysfunction