Fluid movement in capillaries
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