1. Fluid, Electrolyte Balance

2. Osmosis: Water molecules move from the less concentrated area to the more concentrated area in an attempt to equalize the concentration of solutions on two sides of a membrane.

3. Diffusion: The movement of molecules through a semipermeable membrane from an area of higher concentration to an area of lower concentration.

4. Solvent (H20) Movement
Cell membranes are semipermeable allowing water to pass through
Osmosis- major way fluids transported Water shifts from low solute concentration to high solute concentration to reach homeostasis (balance).
Water is a solvent
Concentration of particles in solution (pulling action = osmolarity)
Isotonic have almost same osmolarity as plasma therefore there is no pull

5. Osmolarity Concentration of particles in solution
The greater the concentration (Osmolarity) of a solution, the greater the pulling force (Osmotic pressure)
Normal serum (blood) osmolarity = mOSM/kg
A solution that has HIGH osmolarity is one that is > serum osmolarity = HYPERTONIC solution
A solution that has LOW osmolarity is one that is < serum osmolarity = HYPOTONIC solution
A solution that has equal osmolarity as serum = ISOTONIC solution
Osmosis, by the way, is the reason that drinking salt water will kill you.
The HIGH osmolarity salt water in the GI system rapidly pulls water into the GI system and excretion – rapidly dehydrating cells
SEE NEXT SLIDES FOR FURTHER DISCUSSION

6. Hypertonic Fluids
Hypertonic fluids have a higher concentration of particles (high osmolality) than ICF
This higher osmotic pressure shifts fluid from the cells into the ECF
Therefore Cells placed in a hypertonic solution will shrink

7. Hypertonic Fluids Used to temporarily treat hypovolemia
Used to expand vascular volume
Fosters normal BP and good urinary output (often used post operatively)
Monitor for hypervolemia ! Not used for renal or cardiac disease. THINK – Why not?
D5% 0.45% NS
D5% NS
D5% LR
Used for post op, decreases intracellular edema, fosters normal BP and good urinary output.
D51/2NS, D5NS, D5RL
Hyperal
Pulmonary Edema

8. Cell in a hypertonic solution8

9. Hypotonic Fluids
Hypotonic fluids have less concentration of particles (low osmolality) than ICF
This low osmotic pressure shifts fluid from ECF into cells
Cells placed in a hypotonic solution will swell
ECF- extracellular fluids

10. Hypotonic Fluids Used to “dilute” plasma particularly in hypernatremia
Treats cellular dehydration
Do not use for pts with increased ICP risk or third spacing risk
0.45%NS
0.33%NS

11. Cell in a hypotonic solution11

12. Isotonic Fluid
Isotonic fluids have the same concentration of particles (osmolality) as ICF ( mOsm/L)
Osmotic pressure is therefore the same inside & outside the cells
Cells neither shrink nor swell in an isotonic solution, they stay the same
ICF intracellular fluid - fluid inside the cell
D5W isotonic /Normal saline solution is isotonic because it has almost the same concentration of sodium as blood.
Used to replace Ecvlume

13. Isotonic Fluid Expands both intracellular and extracellular volume
Used commonly for: excessive vomiting,diarrhea
0.9% Normal saline
D5W
Ringer’s Lactate

14. 14

15. Schematic of filtration pressure changes within a capillary bed
Schematic of filtration pressure changes within a capillary bed. On the arterial side, arterial blood pressure exceeds colloid osmotic pressure, so that water and dissolved substances move out of the capillary into the interstitial space. On the venous side, venous blood pressure is less than colloid osmotic pressure, so that the water and dissolved substances move into the capillary.

16. Filtration pressure is the difference between colloid osmotic pressure and blood hydrostatic pressure. These pressures are important in understanding how fluid leaves arterioles, enters the interstitial compartment, and eventually returns to the venules. The filtration pressure is positive in the arterioles, helping to force or filter fluids into interstitial spaces; it is negative in the venules and thus helps fluid enter the venules.

17. Distribution of Body Fluids
Figure 52-1 Total body fluid represents 40 L in an adult male weighing 70 kg (154 lb).

20. Body Fluids Water= most important nutrient for life.
Water= primary body fluid. Adult weight is 55-60% water.
Loss of 10% body fluid = 8% weight loss SERIOUS
Loss of 20% body fluid = 15% weight loss FATAL
Fluid gained each day should = fluid lost each day (2 -3L/day average)

21. Intracellular fluid (ICF)
Fluid Compartments
Extracellular Fluid (ECF)
Fluid outside the cell.
1/3 of body’s H20
More prone to loss
3 types:
Interstitial- fluid around/between cells
Intravascular- (plasma) fluid in blood vessels
Transcellular –CSF, Synovial fluid etc
Intracellular fluid (ICF)
Fluid inside the cell
Most (2/3) of the body’s H20 is in the ICF.
NOTE: Potter & Perry speaks to the “percentage of body weight” % of BODY WEIGHT = ICF fluid % of BODY WEIGHT = ECF fluid
Transcellular fluid is a negligible amount

23. Solute Homeostasis Where sodium goes, water follows.
Diffusion – movement of particles down a concentration gradient. Osmosis – diffusion of water across a selectively permeable membrane Active transport – movement of particles up a concentration gradient; requires energy

30. Electrolytes