Is also called isosmotic volume expansion

(1) ECF volume increases, but no change occurs in the osmolarity of ECF or ICF. Because osmolarity is unchanged, water does not shift between the ECF and ICF compartments.

(2) Plasma protein concentration and hematocrit decrease because the addition of fluid to the ECF dilutes the protein and red blood cells (RBCs). Because ECF osmolarity is unchanged, the RBCs will not shrink or swell.

Volume contraction

Diarrhea

Diarrhea

Liters

Liters

Liters

Adrenal insufficiency

Adrenal insufficiency

Liters

Infusion of isotonic NaCI

Liters

Volume expansion

Volume expansion

Liters

Liters

SIADH

SIADH

Liters

Figure 5-2. Shifts of water between body fluid compartments. Volume and osmolarity of normal extracellular fluid (ECF) and intracellular fluid (ICF) are indicated by the solid lines. Changes in volume and osmolarity in response to various situations are indicated by the dashed lines. SIADH = syndrome of inappropriate antidiuretic hormone.

Table 5-2. Changes in Volume and Osmolarity of Body Fluids

ECF ICF ECF Hct and

Type Key Examples Volume Volume Osmolarity Serum [Na+]

Table 5-2. Changes in Volume and Osmolarity of Body Fluids

ECF ICF ECF Hct and

Type Key Examples Volume Volume Osmolarity Serum [Na+]

Isosmotic volume expansion

Isotonic NaCI infusion

t

No change

No change

I Hct - [Na+]

Isosmotic volume contraction

Diarrhea

I

No change

No change

î Hct - [Na+]

Hyperosmotic volume expansion

High NaCI intake

Î

1

Î

I Hct T [Na+]

Hyperosmotic volume contraction

Sweating Fever

Diabetes Insipidus

I

Î

- Hct T [Na+]

Hyposmotic volume expansion

SIADH

t

t

i

- Hct I [Na+]

Hyposmotic volume contraction

Adrenal insufficiency

4

t

i

t Hct I [Na+]

- = no change; ECF = extracellular fluid; Hct = hematocrit; ICF = intracellular fluid; SIADH = syndrome of inappropriate secretion of antidiuretic hormone.

- = no change; ECF = extracellular fluid; Hct = hematocrit; ICF = intracellular fluid; SIADH = syndrome of inappropriate secretion of antidiuretic hormone.

(3) Arterial blood pressure increases because ECF volume increases.

b. Diarrhea—loss of isotonic fluid

- is also called isosmotic volume contraction.

(1) ECF volume decreases, but no change occurs in the osmolality of ECF or ICF. Because osmolarity is unchanged, water does not shift between the ECF and ICF compartments.

(2) Plasma protein concentration and hematocrit increase because the loss of ECF concentrates the protein and RBCs. Because ECF osmolarity is unchanged, the RBCs will not shrink or swell.

(3) Arterial blood pressure decreases because ECF volume decreases.

c. Excessive NaCl intake—addition of NaCl

- is also called hyperosmotic volume expansion.

(1) The osmolarity of ECF increases because osmoles (NaCl) have been added to the ECF.

(2) Water shifts from ICF to ECF. As a result of this shift, ICF osmolarity increases until it equals that of ECF.

(3) As a result of the shift of water out of the cells, ECF volume increases (volume expansion) and ICF volume decreases.

(4) Plasma protein concentration and hematocrit decrease because of the increase in ECF volume.

d. Sweating in a desert—loss of water

- is also called hyperosmotic volume contraction.

(1) The osmolarity of ECF increases because sweat is hyposmotic (relatively more water than salt is lost).

(2) ECF volume decreases because of the loss of volume in the sweat. Water shifts out of ICF; as a result of the shift, ICF osmolarity increases until it is equal to ECF osmolarity, and ICF volume decreases.

(3) Plasma protein concentration increases because of the decrease in ECF volume. Although hematocrit might also be expected to increase, it remains unchanged because water shifts out of the RBCs, decreasing their volume and offsetting the concentrating effect of the decreased ECF volume.

e. Syndrome of inappropriate antidiuretic hormone (SIADH)—

gain of water

- is also called hyposmotic volume expansion.

(1) The osmolarity of ECF decreases because excess water is retained.

(2) ECF volume increases because of the water retention. Water shifts into the cells; as a result of this shift, ICF osmolarity decreases until it equals ECF osmolarity, and ICF volume increases.

(3) Plasma protein concentration decreases because of the increase in ECF volume. Although hematocrit might also be expected to decrease, it remains unchanged because water shifts into the RBCs, increasing their volume and offsetting the diluting effect of the gain of ECF volume.

Was this article helpful?

+1 0
Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

Get My Free Ebook


Responses

  • PETRA
    What is Isotonic volume expansion?
    3 years ago

Post a comment