Fluid Balance

1. Definitions

1.1. Solutes

1.1.1. Particles that are dissolved or suspended in water

1.2. Hemodilution

1.2.1. Components of blood decrease due to an increase in fluid portion of the blood

1.2.2. decreased hgb, hct, BUN, etc.

1.3. Hemoconcentration

1.3.1. Components of blood increase due to a decrease in fluid portion of the blood

1.3.2. elevated hgb, hct, BUN, etc.

1.4. osmolality

1.4.1. concentration or ratio of solutes to solvents

1.5. intravascular fluid

1.5.1. plasma, vascular space

1.6. interstitial fluid

1.6.1. fluid between cells

2. Fluid Overload

2.1. kidneys increase output and then excrete sodium to correct overload

2.2. causes

2.2.1. excess fluid replacement

2.2.2. excess fluid intake

2.2.3. diseases

2.2.3.1. kidney failure

2.2.3.2. heart failure

2.2.4. long term corticosteroid use

2.3. physical assessment

2.3.1. history

2.3.1.1. medical history

2.3.1.2. dyspnea

2.3.1.3. weight gain

2.3.2. vital signs

2.3.2.1. increased and bounding pulse

2.3.2.2. increased bp

2.3.2.3. increased respiratory rate

2.3.3. distended veins, edema

2.3.4. muscle weakness

2.3.5. dyspnea, crackles in lungs

2.3.6. Cool, pale, skin

2.3.7. altered LOC

2.3.8. enlarged liver

2.4. interventions

2.4.1. diuretics

2.4.1.1. loop diuretic

2.4.1.1.1. monitor output and characteristic

2.4.1.1.2. monitor weight

2.4.2. sodium and fluid restriction

2.4.3. monitor I & O

2.4.4. Patient safety

2.4.4.1. assess every 2 hr

2.4.4.2. monitor for PE

2.4.4.3. monitor for signs of electrolyte imbalance

2.4.4.3.1. sodium and potassium values

2.4.4.3.2. EKG pattern

2.4.4.4. monitor for skin breakdown from edema

3. Dehydration

3.1. types

3.1.1. isotonic dehydration

3.1.1.1. equal amounts of fluid and solids lost

3.1.1.2. treat with iv fluids

3.1.2. hypertonic dehydration

3.1.2.1. more severe and often related to other disease processes

3.1.2.2. hyper sodium in blood stream

3.1.2.3. more water is lost than sodium

3.1.2.4. treat with iv water

3.1.3. hypotonic dehydration

3.1.3.1. more severe and often related to other disease processes

3.1.3.2. hypo sodium in blood stream

3.1.3.3. more sodium is lost than water

3.1.3.4. treat with iv sodium

3.2. causes

3.2.1. excessive loss

3.2.1.1. ex: vomiting, diaphoresis, diuretics

3.2.2. decreased intake

3.2.2.1. ex: impaired thirst, difficulty swallowing, unconsciousness

3.3. assessment

3.3.1. history

3.3.1.1. I & O

3.3.1.2. weight loss

3.3.1.3. risk factors

3.3.1.3.1. medications

3.3.1.3.2. wounds, swallowing, diarrhea, vomiting, etc.

3.3.1.4. kidney function

3.3.2. physical assessment

3.3.2.1. vital signs

3.3.2.1.1. decreased bp

3.3.2.1.2. increased hr

3.3.2.1.3. low grade fever

3.3.2.1.4. increased respiratory rate

3.3.2.2. skin/mucous membranes

3.3.2.2.1. dry, turgor

3.3.2.2.2. tongue furrows

3.3.2.2.3. pallor

3.3.2.3. dizziness

3.3.2.4. decreased urine output

3.3.2.5. mental status

3.3.2.6. weight

3.3.2.6.1. 1 kg= 1 liter of water

3.4. labs

3.4.1. elevated hemoglobin and hematocrit

3.4.2. elevated BUN

3.4.3. serum electrolytes

3.4.4. increased serum osmolarity

3.4.5. elevated urine specific gravity

3.5. interventions

3.5.1. treat by eliminating cause

3.5.2. fluid replacement

3.5.3. oral rehydration solutions

3.5.3.1. glucose and electrolytes

3.5.4. IV fluids

3.5.4.1. isotonic

3.5.4.1.1. no shifting of fluids

3.5.4.1.2. 0.9% saline

3.5.4.1.3. 5% dextrose in water

3.5.4.1.4. lactated ringers

3.5.4.2. hypotonic

3.5.4.2.1. water

3.5.4.2.2. 0.45% saline

3.5.4.3. hypertonic

3.5.4.3.1. 10% dextrose in water

3.5.4.3.2. 5% dextrose in 0.9% saline

3.5.4.3.3. 5% dextrose in 0.45% saline

3.5.4.4. NOTE: Dextrose solutions are hypertonic but are reverted to isotonic once administered because the dextrose is quickly metabolized (used when a small fluid shift is desired)

4. Regulation of Fluid

4.1. CNS thirst drive

4.1.1. sensation of thirst is caused by decreasing blood volume or increasing blood osmolarity

4.2. Pituitary (antidiuretic hormone)

4.2.1. increases reabsorption of water in the kidneys and causes vasoconstriction

4.2.2. in response to increased blood osmolarity

4.3. Renin-Angiotensin II pathway (aldosterone)

4.3.1. increases reabsorption of sodium and water in the kidneys

4.3.2. osmosis is used here, but isn't used in antidiuretic hormone

4.3.3. utilized in more severe situations

4.4. Atrial and Brain (Natriuretic peptide)

4.4.1. inhibits reabsorption of sodium and water in the kidneys

4.4.2. secreted in heart in response to increased blood volume (stretch receptors)

5. Labs & Tests

5.1. Urine Specific Gravity

5.1.1. 1.000-1.030

5.2. Serum Osmolarity

5.2.1. 270-300 mOsm/L

6. Impact of aging on fluid balance

6.1. kidneys

6.1.1. poor excretion of waste products

6.1.2. Increased water loss (risk of dehydration)

6.2. decreased muscular mass

6.2.1. decreased total body water (risk for dehydration)

6.3. diminished thirst reflex

6.3.1. decreased fluid intake (risk for dehydration)

6.4. adrenal atrophy

6.4.1. poor regulation of potassium and sodium (risk for hyponatremia and hyperkalemia)

7. movement and exchange

7.1. osmosis

7.1.1. movement of WATER through a semipermeable membrane

7.1.2. the solvent is moved rather than the solute (like in diffusion)

7.1.2.1. solute cannot move across membrane

7.2. diffusion

7.2.1. movement of particles across a membrane from an area of high particle concentration to an area of low particle concentration

7.2.2. ex: O2 and CO2 in lungs

7.3. filtration

7.3.1. movement of fluid across a cell or blood vessel membrane because of HYDROSTATIC PRESSURE DIFFERENCES on both sides of the membrane

7.3.2. ex: blood pressure

7.3.2.1. must be higher within the vessel than outside the vessel so that fluid may be pushed out of the vessel and to the tissues

7.3.3. example of impaired filtration

7.3.3.1. edema (pressure outside vessel in higher than inside vessel and perfusion is impaired)

7.4. hydrostatic pressure

7.4.1. water pressure

7.4.1.1. caused by fluid volume pressing against the wall of a membrane

7.5. osmotic pressure

7.5.1. the water pulling capacity

7.6. active transport

7.6.1. energy is used to get a substance across a cell membrane

7.6.2. substance is moved in spite of concentration gradient