Notes on Fluid and Electrolytes 4 FLUID VOLUME DEFICIT

FLUID VOLUME DEFICIT

A. Description
1. Dehydration occurs when the fluid intake of the body is not sufficient to meet the fluid needs of the body.
2. The goal of treatment is to restore fluid volume, replace electrolytes as needed, and eliminate the cause of the fluid volume deficit.

B. Types of fluid volume deficits
1. Isotonic dehydration
a. Water and dissolved electrolytes are lost in equal proportions.
b. Known as hypovolemia, isotonic dehydration is the most common type of dehydration.
c. Isotonic dehydration results in decreased circulating blood volume and inadequate tissue perfusion.

2. Hypertonic dehydration
a. Water loss exceeds electrolyte loss.
b. The clinical problems that occur result from alterations in the concentrations of specific plasma electrolytes.
c. Fluid moves from the intracellular compartment into the plasma and interstitial fluid spaces, causing cellular dehydration and shrinkage.

3. Hypotonic dehydration
a. Electrolyte loss exceeds water loss.
b. The clinical problems that occur result from fluid shifts between compartments, causing a decrease in
plasma volume.
c. Fluid moves from the plasma and interstitial fluid spaces into the cells, causing a plasma volume deficit and causing the cells to swell.

C. Causes of fluid volume deficits
1. Isotonic dehydration
a. Inadequate intake of fluids and solutes
b. Fluid shifts between compartments
c. Excessive losses of isotonic body fluids

2. Hypertonic dehydration—conditions that increase fluid
loss, such as excessive perspiration, hyperventilation,
ketoacidosis, prolonged fevers, diarrhea, early-stage
renal failure, and diabetes insipidus

3. Hypotonic dehydration
a. Chronic illness
b. Excessive fluid replacement (hypotonic)
c. Renal failure
d. Chronic malnutrition

D. Assessment
1. Cardiovascular
a. Thready, increased pulse rate
b. Decreased blood pressure and orthostatic (postural) hypotension
c. Flat neck and hand veins in dependent positions
d. Diminished peripheral pulses

2. Respiratory: Increased rate and depth of respirations

3. Neuromuscular
a. Decreased central nervous system activity, from lethargy to coma
b. Fever

4. Renal
a. Decreased urinary output
b. Increased urinary specific gravity

5. Integumentary
a. Dry skin
b. Poor turgor, tenting present
c. Dry mouth

6. Gastrointestinal
a. Decreased motility and diminished bowel sounds
b. Constipation
c. Thirst
d. Decreased body weight

7. Hypotonic dehydration: skeletal muscle weakness

8. Hypertonic dehydration
a. Hyperactive deep tendon reflexes
b. Pitting edema

9. Laboratory findings
a. Increased serum osmolality
b. Increased hematocrit
c. Increased blood urea nitrogen (BUN) level
d. Increased serum sodium level

E. Interventions
1. Monitor cardiovascular, respiratory, neuromuscular, renal, integumentary, and gastrointestinal status.
2. Prevent further fluid losses and increase fluid compartment volumes to normal ranges.
3. Provide oral rehydration therapy if possible and intravenous (IV) fluid replacement if the dehydration is
severe; monitor intake and output.
4. Generally, isotonic dehydration is treated with isotonic fluid solutions, hypertonic dehydration with hypotonic fluid solutions, and hypotonic dehydration with hypertonic fluid solutions.
5. Administer medications as prescribed such as antidiarrheal, antimicrobial, antiemetic, and antipyretic
medications, to correct the cause and treat any symptoms.
6. Administer oxygen as prescribed.
7. Monitor electrolyte values and prepare to administer medication to treat an imbalance, if present.