NCM100 8th F&E

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Fundamentals of Nursing (Hatdog ☺)

Fluids & Electrolyte Balance~

• Why Fluids and Electrolyte is important

- Critical medium in the human body

- Lubricant

- Transporter for nutrients, waste products and other substances

- An insulator and shock absorber

- One means of regulating and maintaining body temperature

• Fluid

- Anything that flows

- Water and electrolytes

• Electrolytes

- Chemical compounds that partially dissociates/separates into particles

• Solution

- Solvent – Fluid (mas madami or malaki)

- Solutes – Electrolytes

Fluid Compartments

• Intracellular Fluid (ICF) is the fluid within the cell (cytosol)

• Extracellular Fluid (ECF) is the fluid outside the cell

o Interstitial fluid – Fluid surrounding the cell

o Intravascular fluid/Plasma – Fluid component of blood

Distribution of Body Fluids

1. Extracellular Fluid (ECF)

a. 35% Body fluids; 20% Body weight

b. Fluid outside the cell

i. Intravascular – “Blood Plasma”

1. 8% of body fluids

2. Fluid within the blood vessel

ii. Interstitial

1. 25% of body fluids

2. Fluid between cell and outside blood vessels

� Transcellular

2. Intracellular Fluid (ICF)

a. 40% Body fluids

b. Fluid inside the cell

Composition of Body Fluids

• Electrolytes

o An element or compound that when dissolved in water, separates into ions that are

electrically charged

o Cations (Positively + charged ions)

� Na+, K

+, Ca

2+

o Anions (Negatively – charged ions)

� Cl-, HCO

-3, SO

-4

• Minerals

o Minerals are ingested as compounds and are constituents of all body tissues and fluids

o They may act as catalysts in response to muscle contraction and metabolism in foods

o Regulate electrolyte balance and hormone production

o Examples: Iron and Zinc


Movement of Body Fluids

1. Osmosis

a. Involves the movement of a pure solvent (water) across a semi permeable membrane from an

area of lower concentration to an area of higher concentration

b. The rate of osmosis depends on the concentration of the solutes in the solution, temperature,

and electrical charges of the solutes

c. Osmotic Pressure is the drawing power of water and depends on the number of molecules in

solution

i. Osmolality – The osmotic pressure of a solution is its Osmolality which is expressed

in osmols or milliosmols per kilogram (mOsm/kg)

1. The normal serum Osmolality is 275 mOsm/kg – 295 mOsm/kg

ii. Osmolarity – Reflects the number of molecules in a liter of solution and is measured

in milliosmols per liter (mOsm/L)

iii. d. Classifications of Solutions

Tonicity Definition Effect on Cell size Osmolality

Hypotonic A solution of lower

osmotic pressure

Swelling Less than 270 mOsm/kg

Isotonic A solution with the

same osmolarity as

blood plasma

None / Equal 275 – 295 mOsm/kg

Hypertonic A solution of higher

osmotic pressure

Shrinking More than 300

mOsm/kg

2. Diffusion

a. Is the random movement of a solute in a solution across a semi permeable membrane from an

area of higher concentration to an area of lower concentration

b. The rate of diffusion is affected by molecule size, concentration and temperature of solution

3. Filtration

a. Is the process by which water and diffusible substances move together across a membrane, in

response to fluid pressure

b. Moving from an area of higher pressure to lower pressure

c. Hydrostatic Pressure

i. A pushing pressure in the arteriole end of the capillary bed created by the heart

pumping

ii. Forces water, oxygen, and nutrients through capillary walls into interstitial spaces

iii.

Capillary

Interstitial Space

Water, Oxygen, Nutrients

are forced out from the capillary


4. Active Transport

a. Active transport requires metabolic activity and expenditure of energy to move substances

across cell membranes

b. An examples is the sodium-potassium-ATPase pump

i. Sodium is pumped out of the cell and potassium is pumped in

c. Active transport is the mechanism by which cells absorb glucose and other substances to carry

out metabolism

Regulation of Body Fluids

1. Fluid Intake

a. Thirst

i. Hypothalamus – Thirst-control center

ii. Osmoreceptors - Monitors the serum osmotic pressure

b. The average adult’s intake is about 2200 – 2700 mL per day

i. Oral intake: 1100 – 1400 mL, 50%

ii. Solid foods 800 – 1000 mL, 40%

iii. Oxidative metabolism 300 mL, 10%

2. Hormonal Regulation (p. 969)

a. Antidiuretic Hormone (ADH) – Stored in the posterior pituitary

i. Released in response to changes in osmolarity

ii. b. Renin-Angiotensin-Aldosterone System (RAAS)


c. Atrial natriuretic peptide (ANP)

i. A hormone secreted from Atrial cells of the heart in response to Atrial stretching and

an increase in circulating blood volume

ii. It acts as a diuretic that causes sodium loss and inhibits the thirst mechanism

Fluid Output Regulation (Kidneys, skin, lungs, and GI Tract)

• Insensible Water loss

o Occurs through the skin and lungs

� Skin – Is either sensible/insensible. 500 – 600 mL

� Lungs – Expires about 500 mL of water daily

• Sensible Water loss

Kidney – Receives approximately 180 L of plasma to filter each day and produces 1200 – 1500 mL of

urine

GI Tract – The normal adult loses 200 mL of the 3 – 6 L each day through feces

Regulation of Electrolytes

Cations

1. Potassium (K)

a. Potassium (K+) is the dominant intracellular electrolyte

b. It is the primary buffer in the cell

c. Normal serum is 3.5 – 5.0 mEq/L

Functions:

� Neuromuscular irritability, the ability of nerve and muscle cells to fire (depolarize)

� Cardiac impulse conduction and muscle contractility

� ICF osmolarity (cell osmotic pressure)

� Regulation of acid-base balance

� Activation of enzyme reactions

� Influencing kidney function

Movement of Potassium is influenced by:

� Changes in pH

� Insulin

� Adrenal hormones

� Changes in serum sodium

2. Sodium (Na)

a. Sodium (Na) is the dominant electrolyte in the ECF.

b. Sodium is the chief base of the blood

c. Normal serum levels is 135 - 145 mEq/L

Na affects the fluid volume of the ECF and is regulated, in part, by:

� Aldosterone

� Renal blood flow

� Renin secretion

� Antidiuretic Hormone (ADH) due to its effect on water

� Estrogens

� Carbonic anhydrase enzyme

The regulation of the body’s water and electrolyte status by the kidneys is influenced by the ECF sodium

concentration


Functions:

� Neuromuscular irritability

� Conduction of nerve impulses and muscle contraction

� Osmotic pressure of the ECF

� Acid-base balance

� Water balance

� Gland secretions

3. Calcium (Ca)

a. The normal serum calcium level is 4.5 – 5.5 mEq/L

b. About 98% of calcium is stored in the bones and teeth

c. About 50% of calcium in the blood is bound to protein

d. Muscle cells store calcium

Several factors influence serum calcium levels, including:

� Parathyroid hormone (PTH)

� Calcitonin

� Vitamin D

� Estrogens and androgens

� Carbohydrates and lactose


Calcium balance is also influenced by:

� Absorption of calcium from the gastrointestinal tract

� Excretion of calcium in urine and feces

� Deposition and resorption of bone


Calcium functions in:

� Muscle contractile ability

� Correct neural function

� Development and strength of bones and teeth (also requires vitamin D and phosphorus)

� Blood clotting

4. Magnesium (Mg)

a. The normal serum level of magnesium (Mg) is 1.5 – 2.5 mEq/L

b. Mg is absorbed from food and lost via urine and stool

c. About 1% is found in the ECF, 60% is in the bone, and the remainder is in muscle and soft

tissue

d. About 1/3 of Mg is bound to protein

e. 2/3 of Mg is free in the plasma

f. Mg is the second highest electrolyte in the ICF, second only to potassium

g. Mg and Ca are tied together, thus a deficiency of one affects the other

Magnesium is an important electrolyte which:

� Affects skeletal muscles by depressing acetylcholine release at synaptic junctions

� Regulates neuromuscular irritability (excitability)

� Aids absorption of calcium from the intestine

� Aids calcium metabolism

� Affects parathyroid hormone secretion and therefore intracellular calcium

� Aids transport of potassium and sodium across membranes

� Is required for use of ATP as a source of energy

� Activates enzymes which influence protein and nucleic acid synthesis

� Assists in cell metabolism

� Regulates ICF concentrations of potassium, calcium and phosphorus

� Aids blood clotting

Anions

1. Chloride (Cl)

a. The normal serum level of Cl is 95 – 105 mEq/L

b. Cl is taken into the body via food and excreted by the kidneys

c. Cl is mainly in the ECF, with less amounts in the interstitial and intracellular fluids

d. Cl is found in gastrointestinal fluids

e. Cl concentration increases / decreases with changes in the concentration of other anions

f. Chloride competes with bicarbonate to combine with sodium

i. If the Cl level drops, bicarbonate level increases

g. If sodium is reabsorbed as a result of aldosterone, there will be an increased reabsorption of

chloride

h. Chemically, chloride is usually in combination with HCl and NaCl

Functions:

� Aiding cell integrity by influencing osmotic pressure


� Water balance

2. Phosphorus (P) / Phosphate (PO43-

)

a. The normal serum level is 1.7 – 2.6 mEq/L (2.8 – 4.5 mg/dL)

b. It is the most abundant anion (negative charge) in the ICF


c. Phosphorus is regulated by the parathyroid hormone (PTH)

� PTH causes phosphorus to move from bone to plasma

d. About 80-85% of the total phosphorus content in the body is combined with calcium in the

bones and teeth, the rest is in the blood as phosphate or esters

e. Phosphorus enters the cell with glucose and is lowered after carbohydrate ingestion

f. Calcium and phosphorus levels are evaluated in relationship between the two

� If Ca is reduced, P will increase

g. An excess in the serum level of Ca (or P) will cause the kidney to excrete the other

Functions:

� Formation of bone

� Regulating the level of a substance in red blood cells which reduces the affinity of hemoglobin for

oxygen


� Storage and transfer of energy from one site to another

“Para kang Hydrogen ion! MAHILIG kang kumapit sa iba! �”

- Lol hahahaha ☺

NCM100 8th F&E

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