NU 116 Fluids, Electrolytes, Acid-Base Balance

body fluid

-primarily water
-contains gases (CO2 & O2)
-contains solutes

electrolytes

solutes that develop an electrical charge when dissolved in water
(sodium, potassium)

nonelectrolytes

solutes that do not conduct electricity
(glucose, urea)

60%

what percent of body weight in a typical adult is body fluid
(decreases with age)

adipose tissue
age
sex

total body water content varies with what 3 factors?

Intracellular fluid (ICF)

fluid within cells
-40% of body weight (2/3 of body fluid)
-essential for cell function and metabolism

Extracellular fluid (ECF)

fluid outside the cells
-20% of body weight (1/3 of body fluid)
-carries water, electrolytes, nutrients, and oxygen to cells and removes waste products of cellular metabolism

intersitial fluid

extracellular fluid in the spaces between cells
-excess fluid here = edema

intravascular fluid

extracellular fluid within the blood (plasma)
-main function is to transport blood cells

transcellular fluid

extracellular fluid, includes specialized fluids that are contained in body space
-cerebrospinal, pleural, peritoneal, synovial fluid, and digestive juices

cations

electrolytes that carry a positive charge
-sodium, potassium, calcium, magnesium, hydrogen ions

anions

electrolytes that carry a negative charge
-chloride, phosphate, bicarbonate

passive transport

the movement of substances across a cell membrane without the use of energy
-osmosis, diffusion, filtration

osmosis

movement of WATER across a membrane from an area of LOW to HIGH concentration

osmolality

concentration of solutes creating pressure in the body fluid

sodium

greatest determinant of serum osmolality

isotonic solution

same solute concentration on both sides of membrane (so no mvmt of water will occur)
-useful for client with hypotension or hypovolemia (FVD)

hypotonic solution

Solute concentration is less than that inside the cell; cell gains water (swells)
-used for hyperglycemia (diabetes ketoacidosis)

hypertonic solution

Solute concentration is greater than that inside the cell; cell loses water (swells)
-used to increase blood volume (with burns or hemorrhage)
-stabilizes BP, increases urine output, reduces edema

diffusion

movement of SOLUTES through a cell membrane from an area of HIGH to LOW concentration
-untill dynamic equilibrium

filtration

movement of WATER AND SMALL PARTICLES from an area of HIGH PRESSURE to one of LOW PRESSURE
-pressure created when hydrostatic pressure exceeds orthostatic pressure -- force moves water and solutes

hydrostatic pressure

force created by fluid that pushes fluid out of the vessel, responsible for normal circulation of blood

osmotic pressure

power of a solution to draw in water

active transport

Energy-requiring process that moves material across a cell membrane against a concentration gradient (LOW to HIGH concentration)
-ATP
-sodium-potassium pump

fluid intake

-80% from drinking fluids (2700-3500 mL/day)
-20% from food and metabolism
-thirst is major regulator (thirst center in hypothalamus)

hypothalamus

changes in plasma concentration (osmolality) signal the thirst center in the ___ --> urge to drink

urine
skin
lungs
feces

common sources of fluid loss (4)

kidneys

principle regulator of fluid and electrolyte balance

ADH (antidiuretic hormone)

causes kidneys to retain fluid
-if fluid volume is low, this is released

Renin-Angiotensin System

when ECF volume is decreased, retain sodium and water
-directs adrenal cortex to release aldosterone

thyroid hormone

affects fluid volume by influencing cardiac output

Aldosterone

salt-retaining hormone" which promotes the retention of sodium by the kidneys, and excretion of potassium
-released via renin-angiotensin system

3.5-5.0

Potassium (K+) normal range

135-145

Sodium (Na+) normal range

8.5-10.5

Calcium (CA2+) normal range

1.6-2.6

Magnesium (Mg2+) normal range

95-105

Chloride (Cl-) normal range

22-26

Bicarbonate (HCO3-) normal range

35-45

Carbon dioxide (PCO2) normal range

7.35-7.45

pH normal range

Sodium (Na+)

regulates fluid volume
-reabsorbed and secreted thru kidneys
-deficiency may be caused by excess water
-major cation in the ECF

potassium (K+)

-regulates cardiac rhythm
-excreted thru kidneys, regulated by aldosterone
-loss triggered by diuretics--> dysrhythmias
-major cation in the ICF

calcium (Ca2+)

#NAME?

Magnesium (Mg2+)

#NAME?

acidosis

pH < 7.35

alkalosis

pH > 7.45

acid

any compound that contains hydrogen ions (H+)

base

compound that accepts (combines with) hydrogen ions