interactive tutorial: fluid and electrolytes

Extracellular and intracellular fluid are separated by

the cell membrane

extracellular fluid

is outside the cell and comprises of 1/3 of the body's water

intracellular fluid

is within the cells and comprises of 2/3 of the body's water

Extracellular fluid

is found in the vascular compartment and interstitial space

vascular compartment consists of

arteries veins and capillaries and contains plasma

interstitial space

is area surrounding the cell

intracellular fluid

is primarily water

extracellular fluid

is primarily saline (sodium chloride, bicarbonate, and protein

capillary membranes separate

intravascular and interstitial spaces

solutes and water move in

both directions through semipermeable membranes

Fluids and solutes of body are

continuously shifting from one fluid compartment to another to maintain homeostasis.

The mechanisms of maintenance include

active transport and passive transport

Active transport

is a passage of ions or molecules across a cell membrane by an energy consuming process against their concentration gradient (from low to high)

Passive transport

is a passage of ions or molecules across a cell membrane without requiring energy and moves molecules along their concentration gradient (from high to low)

The three types of passive transport

is osmosis, diffusion, and filtration.

*Osmosis*

Movement of water through a semipermeable membrane from an area of low solute concentration to an area of high solute concentration until equilibrium is reached. FLUID LOW TO HIGH Ex. Water moving into a dry sponge.

*Diffusion*

Movement of molecules from an area of high concentration to a less concentrated area until evenly spread out (equilibrium). MOLECULES HIGH TO LOW Ex. Perfume spreading in a room.

*Filtration*

Movement of water and solutes from on area of higher hydrostatic pressure to an area of lower pressure. PRESSURE HIGH TO LOW. Ex. Coffee passing through a filter while grounds stay behind.

Sodium potassium pumps

are active transport

>295 mOsm/kg

hypersolmalality

< 275 mOsm/kg

hypoosmolality

Osmolality affects

tonicity

*Osmolality*

The concentration of solute particles (like sodium, glucose, and urea) in a solution, measured in milliosmoles per kilogram (mOsm/kg) of water. It determines how "concentrated" a fluid is.

*Serum Osmolality*

The measure of solute concentration in blood serum. It helps assess hydration status and detect imbalances like dehydration or overhydration.

Normal range of Osmolality

*275-295 mOsm/kg*.

*Tonicity*

The ability of a solution to make water move in or out of a cell, affecting its size. It depends on *non-penetrating solutes* that cannot cross the cell membrane.

Osmotic pressure occurs between

a solution and pure solvent

*Isotonic Solutions*

Solutions that have the same solute concentration as the inside of a cell, meaning there is no net movement of water in or out of the cell. The cell stays the same size. *Ex.* Normal saline (0.9% NaCl) is an isotonic IV fluid used to maintain fluid balance.

*Osmotic Pressure*

The force that pulls water across a membrane due to differences in solute concentration. The higher the solute concentration, the greater the osmotic pressure. *Ex.* Blood has osmotic pressure that helps pull water from tissues into capillaries to maintain blood volume.

Examples of Isotonic solutions

Normal saline (0.9% NaCl), lactated ringer's solution, 5% dextrose in water (D5W)

Hypotonic solutions have

lower pressure than blood.

Hypotonic solutions would be

1/2 normal saline and 2.5 dextrose in water.

*Hypertonic Solution*

A solution with a higher concentration of non-penetrating solutes than inside the cell, causing water to move *out of the cell, making it shrink. Ex.* 3% NaCl (hypertonic saline) draws water out of cells to reduce swelling in conditions like cerebral edema.

*Hyperosmolar Solution*

A solution with a high osmolality (more solute particles per kilogram of solvent) compared to normal body fluids. It includes both penetrating and non-penetrating solutes. *Ex.* Mannitol (used to reduce brain swelling) is hyperosmolar but does not significantly affect tonicity because it can cross membranes.

Hypertonic Solutions have a pressure higher/lower than blood

Higher osmotic pressure than blood

Examples of Hypertonic Solutions

5% dextrose in normal saline, 5% dextrose in lactated Ringer's solution

Fluid intake and output and nearly equal in a

healthy person

The body balances fluid volume through

Thirst, kidneys, renin-angiotensin-aldosterone system, antidiuretic hormone (ADH or vasopressin), atrial natriuretic peptide (ANP)

renin-angiotensin-aldosterone mechanism process

initiated by decreased perfusion to the kidneys, the kidneys release renin, the renin combines with angiotensinogen to form angiotensin l, angiotensin l is converted in the lungs to angiotensin ll, angiotensin ll stimulates the adrenal cortex to release aldosterone, aldosterone directs the kidney to reabsorb more sodium, water follows sodium back into extracellular fluid

antidiuretic hormone (ADH)

secreted by the posterior pituitary gland, released in response to increased osmolality, increases water retention.

Atrial natriuretic peptide

released by the atria and decreases fluid retention

How does atrial natriuretic peptide decrease fluid retention

by blocking the secretion and action of aldosterone and inhibiting renin secretion

Hypovolemia

fluid volume deficit or diminished blood volume

Causes of hypovolemia

fluid loss, reduced fluid intake, fluid shift out of vascular space

conditions that can result in hypovolemia

fluid loss - hemorrhage, frequent urination, vomiting, diarrhea, fistulas, fever, excessive nasogastric suctioning. reduced fluid intake - dysphagia, unconscious states, lack of fluids, lack of water when recieving conentrated tube feedings, reduced ability to taste (old ppl). Fluid shift out of vascular space - burns, acute intestinal obstruction, pancreatitis, crushing injuries

clinical manifestations of hypovolemia

hypotension, tachycardia, thirst, poor skin turgor, dry mucous membranes, decreased piss, flattened neck veins, If severe - SHOCK.

treatment of hypovolemia

oral or parenteral fluids, blood or blood products if its due to hemorrhage, antidiarrheals if the loss is from diarrhea, antiemetics if its due to vomiting, vasopressors if patient is in hypovolemic shock.

types of fluid volume excess (name them)

hypervolemia, edema, third spacing (when too much fluid moves from intravas space (blood vessels) to the interstitial space (nonfunctional area between the cells))

Edema

excessive accumulation of fluid in the interstitial space

Edema types (2)

local or generalized

Third spacing

extracellular fluid becomes trapped in a space where its unable to be utilized or excreted, types are ascites or pleural effusion

types of third spacing and describe them

ascites - accumulation of serous fluid in the peritoneal cavity which is the abdomen. Pleural effusion is increased fluid in the pleural space which can cause shortness of breath by compression of the lung.

What are some causes of hypervolemia

kidney failure (fluid doesnt get filtered and stays in the body, heart failure (left sided causes edema), cirrhosis (END stage liver disease results in jaundice and ascites), nephrotic syndrome (kidney leaks out too much albumin which is a protein that helps retain water in the BLOOD vessels)

Clinical indications of hypervolemia

dyspnea, crackles, tachypnea, bounding rapid pulse, hypertension, distended neck veins, edema, ventricular gallop, clammy skin

Treatment for hypervolemia

identify and treat the underlying cause, restrict sodium and water fluid intake, if severe - oxygen therapy, morphine, IV diuretics, and mechanical ventilation

Dysphagia

inability to consume oral fluids

Hemorrhage

severe blood loss

Tachycardia and hypotension is a clinical manifestation of hyper/hypo volemia

hypovolemia

Hypovolemic shock clinical manifestation decreased preload, decreased cardiac output

Gastrointestinal fluid loss clinical manifestations

Vomiting, diarrhea

Tachypnea, distended neck veins, and edema is a clinical manifestation of hyper/hypo volemia

hypervolemia

Ascites

excess fluid accumulation in the peritoneal cavity

Edema

excess extracellular fluid

What are the two most important assessments to make for evaluating fluid balance?

Accurate intake/output and daily weight

Electrolytes will conduct

Electricity

Cations

positively charged ions

Anions

negatively charged ions

Sodium

the major cation of extracellular fluid, most plentiful extracellular ion in the body, often combines with chloride

What other electrolyte does sodium combine with?

Chloride

What is the normal serum rate for Sodium

135 to 145 mEq/L

How does the body regulate sodium?

Dietary intake, excretion, kidneys, hormonal regulation like aldosterone or antidiuretic hormone (ADH or vasopressin)

Hyponatremia lvl

Serum sodium level BELOW 135 mEq/L

Hypernatremia lvl

Serum sodium level ABOVE 145 mEq/L

Causes of hyponatremia

EXCESSIVE DIURESIS (EXCESSIVE production of urine) - due to diuretic therapy and nephritis (inflammation of the kidneys), EXCESSIVE SWEATING with nonsodium fluid replacement, GI FLUID LOSS - vomit, diarrhea, fistula (they leak fluid), and adrenocorticoid insufficiency. EXCESS OF WATER - due to excess of oral fluids, excess of parenteral administration of dextrose and water solutions, SIADH, excessive IV administration

What happens to the body without aldosterone? Aldosterone normally signals the kidneys to reabsorb sodium and excrete potassium. Without it, you lose sodium and retain potassium—that's why patients with Addison's often have hyponatremia AND hyperkalemia.

Causes of hypernatremia

INTAKE OF EXCESSIVE SODIUM - due to rapid infusion of hypertonic saline, sodium bicarbonate or isotonic saline. drinking salt water, ingesting large amounts of salt without increasing water intake. LOSS OF WATER - due to diarrhea, increase in insensible loss, diabetes insipidus, decreased water intake, unavailability of water, withholding of water, impaired thirst center.

Psychogenic polydipsia

excessive thirst and compulsive water drinking. can cause hyponatremia

What does excessive administration of 5% dextrose in water cause and what is the rationale?

*causes hyponatremia because the dextrose is metabolized, leaving behind free water* that dilutes the sodium in the bloodstream.

What does frequent tap water enemas cause and what is the rationale?

*Frequent tap water enemas can cause hyponatremia* due to absorption of hypotonic water into the bloodstream, which dilutes sodium levels.

What are manifestations of Hyponatremia

Manifestations of hyponatremia

apprehension, headache, personality changes, anorexia, nausea, vomiting, muscle cramps, depression, lethargy, weakness, disorientation, orthostatic hypotension, obtundation, agitation, decrease in deep tendon reflexes, edema. severe hyponatremia can cause permanent neurological deficits, coma, seizures, and death

Manifestations of hypernatremia

thirst, dry and sticky mucous membranes, decreased skin turgor, weak and rapid pulse, decreased blood pressure, oliguria or anuria, irritability, decreased reflexes, disorientation, and hallucinations

treatment of hyponatremia

identify cause, restrict fluid intake, administer hypertonic 3% sodium chloride solution slowly and with caution

treatment with hypernatremia

administer hypotonic solution such as 0.45 NaCl or 0.3% NaCl. if diabetes insipidus is the cause of hypernatremia, desmopressin or vasopressin may be ordered

Fluid excess is common with

SIADH

Hypertonic 3% NaCl is adminstered slowly and cautiously because

it can cause fluid overload and cerebral edema

Hyponatremia is associated with intracellular

fluid excess

True or false Hyponatremia will cause an increase in vascular fluid volume

FALSE hyponatremia will cause A DECREASE in vascular fluid volume. *Sodium is essential for maintaining vascular volume meaning Sodium helps to maintain osmotic pressure* in the blood vessels. When sodium is low, this pressure decreases, and water shifts into tissues and cells.

Potassium

a major CATION within the body's cell. It is essential in creating the resting membrane potential in neuromuscular tissue. Transforms carbohydrates into energy. Changes glucose into glycogen. Helps build up amino acids into protein. Maintains electrical activity in the heart.

Potassium normal serum range

3.5 to 5.0 mEq/L

Why is the *resting membrane potential* crucial to the body?

because it sets the stage for the cell to respond to stimuli. If the resting membrane potential is too high or too low, the cell will not function properly. For example, if potassium levels are too low (hypokalemia), the resting membrane potential becomes more *positive*, making it harder for the cell to respond to stimuli and perform actions like contraction (in muscle) or transmitting nerve impulses.

How does the body regulate potassium

dietary intake, excretion from the kidneys and hormonal regulation (aldosterone).

What do the mineralocorticoids do? Primarily aldosterone, cause the kidneys to retain sodium and excrete potassium

Hypokalemia lvl

LOWER than 3.5 mEq/L

Hyperkalemia lvl

HIGHER than 5.0 mEq/L

Causes of Hypokalemia

excessive alcohol drinking, excessive steroid therapy, hyperalimentation, inadequate intake - administration of potassium free parenteral solutions, inability to eat, anorexia nervosa, potassium-deficient diet. excessive renal losses - diuretic phrase of renal failure, diuretic agents/therapy (except potassium sparing diuretics), increased mineralocorticoid levels (hyperaldosteronism, corticosteroid drugs, CUSHINGS syndrome). Excessive gastrointestinal losses - diarrhea, draining GI fistula, GI suction, vomiting. Transcompartmental shift - administration of beta-adrenergic agonistics (albuterol), administration of insulin for treatment of diabetic ketoacidosis, metabolic or respiratory alkalosis.

What is hyperalimentation

Administration or consumption of nutrients beyond minimum normal requirements in an attempt to replace nutritional deficiencies.

What is cushings syndrome?

A Disorder resulting from increased adrenocortical secretion of cortisol. Can cause Hypokalemia

Clinical manifestations of hypokalemia

Impaired ability to concentrate urine - polydipsia, polyuria, urine with low specific gravity and low osmolality. Gastrointestinal manifestations - abdominal distention, anorexia, nausea, vomiting, paralytic ileus, hypotonic bowel sounds. Neuromuscular manifestations - muscle flabbiness, weakness, fatigue, muscle cramps/tenderness, paresthesia, paralysis. Cardiovascular manifestations - cardiac arrhythmias, changes in ECG, increased sensitivity to digitalis toxicity, postural hypotension. Central nervous system manifestations - Confusion, depression. Acid-base disorders - metabolic alkalosis. Can also cause apnea

What are the ECG changes with HYPOkalemia?

Flattened T wave, prolonged PR interval, large U wave.