Fluid movement in capillaries

The plasma flows through the capillary but its amount and direction in/out is determined by
- Capillary hydrostatic pressure (out the capillaries)
- Plasma oncotic pressure (into the capillaries)
- Interstitial hydrostatic pressure (into the capillaries)
- Interstitial oncotic pressure (out the capillaries)
Fluid shifts
- Plasma-to-interstitial fluid shift results in edema
  - Elevation of venous hydrostatic pressure
  - Decrease in plasma oncotic pressure
  - Elevation of interstitial oncotic pressure
- Interstitial fluid drawn into plasma decreases edema

Fluid spacing

Used to describe the distribution of body water
- First spacing- Normal distribution
- Second spacing- Abnormal (edema)
- Third spacing- Fluid is trapped where it is difficult or impossible for it to move back into cells or blood vessels
Normal fluid balance

Intake
Fluids	1200 mL
Solid food L	1000 m
Water from oxidation	300 mL
Total	2500 mL

Output
Insensible loss (skin and lungs)	900 mL
In feces	100 mL
Urine	1500 mL
Total	2500 mL

Extracellular fluid volume imbalances

ECF volume deficit (hypovolemia)
- Abnormal loss of body fluids, inadequate fluid intake, or plasma to interstitial fluid shift
- Clinical manifestations related to loss of vascular volume as well as CNS effects
- Correct the underlying cause and replace water and electrolytes (Oral, Blood products, and IV Fluids)
Fluid volume excess (hypervolemia)
- Excess intake of fluids, abnormal retention of fluids, or interstitial-to-plasma fluid shift
- Clinical manifestations related to excess volume
- Remove fluid without changing electrolyte composition or osmolality of ECF (diuretics, fluid restriction, sodium restriction