Contain different electrolytes because the cell membranes separating the two compartments have selective permeability. Contain different solutes, concentration levels are about equal when balance is maintained.
FLUID MOVEMENT A mechanism that regulates fluid and electrolyte balance. Body fluids are in constant motion. Nutrients , waste products, and other substances get into and out of cells, organs, and systems. Influenced by membrane permeability and colloid osmotic and hydrostatic pressures.
Osmosis Movement of water across a semipemeable membrane from an area of low solute concentration (less concentrated) to an area of high solute concentration (more concentrated).
Capillary filtration and reabsorption Filtration – movement of substances from an area of high hydrostatic pressure to an area of lower hydrostatic pressure Hydrostatic pressure – pressure at any level on water at rest due to weight of the water above it. Pushes fluids and solutes through capillary wall pores and into the ISF. Capillary Reabsorptionby the osmotic or pulling force of albumin (Colloid Osmotic/Oncotic Pressure) - pulling force of albumin in the capillaries, attracting water in from the interstitial space
Osmolarity Concentration of a solution. Expressed in milliosomols of solute per liter of solution (mOsm/L) Same osomolarity as other body fluids about 300 mOsm/L
Three Main Types of IV Solutions Isotonic Hypotonic Hypertonic
Isotonic Solutions(240-340mOsm) Solution has the same solute concentration (or osmolality) as normal blood plasma (290mOsm) and other body fluids Solution stays where it is infused, inside the blood vessel Expands the intravascular compartment Does not affect the size of the cells Solution maintains body fluid balance
Isotonic Solutions Nursing considerations Monitor patient for signs of fluid overload especially in patients with CHF and hypertension.
Hypotonic Solutions Solution has a lower osmolarity than serum (less than 240 mOsm/L) Solution causes a fluid shift out of the blood vessels into the cells and interstitial spaces Solution hydrates cells while reducing fluid in the circulatory system Ex.: ½ NSS (0.45% NaCl)
Hypotonic Solutions Nursing considerations Administer cautiously Solution can lower blood pressure Do not give if these solutions if the patient is at risk for: ICP from cerebrovascular accident Head trauma Neurosurgery
Hypertonic solutions Solution has an osmolarity higher than serum(>340mOsm/L) Causes the solute concentration of the serum to increase pulling fluid from the cells and the interstitial compartment into the blood vessels Reduces the risk of edema, stabilizes blood pressure, and regulates urine output
Hypertonic Solutions Nursing considerations Monitor your patient for circulatory overload Solution can be irritating to the vein
Two Main Groups of IV Solutions Crystalloids Colloids
Crystalloids Are isotonic and remain isotonic in the vasculature and are therefore effective volume expanders for a short period of time. Ideal for patients who need fluid volume replacement Ex.: Lactated Ringer’s (LR), Normal Saline (NS)
Colloids Used to increase vascular volume rapidly drawing fluid from the interstitial and intracellular compartments into the vascular compartment. They work well in reducing edema (as in pulmonary or cerebral edema) while expanding the vascular compartment. Examples: albumin, mannitol, dextran, hetastarch, gelafundin, Haesteril
Colloids Dextran Polysaccharide fluid Albumin Natural plasma protein from donor plasma Mannitol Sugar alcohol substance Hetastarch Synthetic colloid made from starch