Homeostasis: Fluid Balance and Disturbance

Vocabulary flashcards covering the concepts of homeostasis, fluid compartments, movement of fluids, and clinical management of fluid volume deficits and excess.

Homeostasis

A relatively stable state of equilibrium or a tendency toward such a state between the different but interdependent elements or groups of elements of an organism.

Fluid and Electrolyte Balance

Process of regulating the extracellular fluid volume, body fluid osmolality, and plasma concentrations of electrolytes.

Intracellular Fluid (ICF)

Fluid located in body cells, representing $2/3$ of the total body fluids in adults.

Extracellular Fluid (ECF)

Fluid consisting of intravascular (plasma), interstitial, lymph, and transcellular fluids.

Transcellular fluids

Specific extracellular fluids including cerebrospinal, pericardial, pancreatic, pleural, intraocular, biliary, peritoneal, and synovial fluids.

Diffusion

The movement of molecules from high concentration to low concentration where both solute and solvent move.

Osmosis

The movement of solvent (water) across a semipermeable membrane from high to low solvent concentration, where only the solvent moves.

Organs of fluid loss

The kidneys, skin, lungs, and GI tract.

Isotonic Solutions

Intravenous solutions such as $0.9\%$ NaCl (NSS), Lactated Ringers (LR), and $5\%$ dextrose in water ($D5W$).

Hypotonic Solutions

Intravenous solutions such as $0.45\%$ NaCl.

Hypertonic Solutions

Intravenous solutions such as $3\%$ NaCl and $5\%$ NaCl.

Hypovolemia

A lack of water and electrolytes causing a decrease in circulating blood volume.

Dehydration

A lack of fluid in the body causing a shift of water from the plasma into the interstitial space.

Fluid Volume Deficit Labs

Laboratory findings including increased Hemoglobin and hematocrit (unless due to blood loss), increased serum/urine osmolality, increased urine specific gravity, and a BUN: creatinine ratio $> 20:1$.

Gerontologic Considerations

Age-related factors for fluid imbalance including decreased thirst sensation, decreased renal capacity, and decreased muscle mass leading to decreased body fluid.

Fluid Volume Excess Risk Factors

Conditions such as heart failure, cirrhosis, kidney failure, excessive sodium or water intake, and SIADH.

SIADH

Syndrome of inappropriate antidiuretic hormone.

Fluid Volume Excess Clinical Manifestations

Includes tachycardia, hypertension, tachypnea, bounding pulse, dyspnea, orthopnea, crackles, edema, distended neck veins, weight gain, and ascites.

Weight to Fluid Correlation

The assessment standard where $1\,kg$ of body weight is approximately equal to $1\,liter$ of fluid.