Ch 6: Fluid, Electrolyte, Acid-Base Homeostasis Pt 1

Intracellular Fluid (ICF)

fluid inside cells

Approximately 40% of total body weight

Total space within cells primarily defined as cytoplasm of cells

Extracellular Fluid

fluid outside the cell

Interstitial fluid (ISF)

between the cells

Intravascular fluid

inside the blood vessels

Transcellular fluid (TSF)

(i.e., CSF; pleural & pericardial cavities; joint spaces)

Osmolarity

a measure of the concentration of particles of a solute in a liter of the liquid in which they are dissolved (solvent).

Tonicity

the capability of a solution to modify the volume of cells by altering their water content. The effect of a solution on cell volume

osmotic pressure of two solutions separated by a semipermeable membrane

Osmosis

Movement of water across a semipermeable membrane (from an area of low solute concentration to an area of high solute concentration).

Diffusion

Water moves from an area of higher water concentration to an area of lower concentration. Movement depends on hydrostatic (push) and osmotic (pull) pressures.

Isotonic solutions

Equal solute concentrations, causes no fluid shifts

Hypotonic solutions

Lower solute concentrations, causing fluids to shift out of the intravascular compartment > intracellular space

Hypertonic solutions

Higher solute concentrations, causing fluids to shift from the intracellular compartment > the intravascular space

Fluid Balance Pressures

Because water moves freely across cell membranes, equilibrium is usually easy to achieve

Movement of water depends on hydrostatic (push) and osmotic (pull) pressures

Osmotic pressure

The "pulling" force on water due to the presence of solutes in solution. Regulated by the plasma protein, Albumin

Hydrostatic pressure

forces fluid out of the capillary, osmotic pressure draws fluid back in

Blood Pressure

Fluid sources

Oral intake, intravenous solutions (iso-, hypo-, or hypertonic)

Fluid lossess

sensible (urine, feces); insensible (sweat, respirations

Thirst mechanism in hypothalamus

triggered by decreased blood volume and increased osmolarity

Antidiuretic Hormone (ADH)

released from pituitary gland and promotes reabsorption of water in the kidneys

Aldosterone

increases reabsorption of sodium and water in the kidneys (renal tubules)

Atrial natriuretic peptide (ANP)

stimulates renal vasodilation and suppresses aldosterone, increasing urinary output

Edema

￭Excess fluid in the interstitial space

￭Issue with distribution, not always fluid overload

Anasarca

generalized edema

Hypervolemia/Fluid volume excess

￭Excess fluid in the intravascular space

￭Excessive sodium or water intake & insufficient losses

Water Intoxication

￭Excess fluid in the intracellular space

￭May lead to rupture (lysis) of the cells with cerebral cells being most sensitive

Excessive Sodium or Water intake Causes

￭High-sodium diet

￭Psychogenic polydipsia (excessive thirst)

￭Hypertonic fluid administration (where is the fluid going?)

￭Free water

￭Enteral feedings

Inadequate sodium or water elimination Causes

￭Hyperaldosteronism

￭Cushing's syndrome

￭Syndrome of inappropriate antidiuretic hormone

￭Renal failure

￭Liver failure

￭Heart failure

Excess Fluid Manifestations

Peripheral edema

Periorbital edema

Anasarca (general swelling in the entire body)

Cerebral edema

Rapid weight gain

Dyspnea, crackles

Bounding pulse, tachycardia, hypertension

Jugular vein distension

Polyuria

Bulging fontanelles (in babies)

Fluid Deficient

total body fluid levels insufficient to meet body's needs

Dehydration

body loses more fluid than what is taken in

Hypovolemia or fluid volume deficit

Decreased fluid in the intravascular space

can occur independently without electrolyte defects

Decrease in fluid level

leads to increase in level of blood solutes, cell shrinkage, and hypotension

Inadequate Fluid Intake Causes

￭Poor oral intake

￭Inadequate IV fluid replacement

Excessive fluid or sodium losses causes

￭Gastrointestinal losses

￭Excessive diaphoresis

￭Prolonged hyperventilation

￭Hemorrhage

￭Nephrosis

￭Diabetes mellitus

￭Diabetes insipidus

￭Burns

￭Open wounds

￭Ascites

￭Effusions

￭Excessive use of diuretics

Osmotic diuresis

Fluid Deficit Manifestations

thirst

dry mucous membranes

decreased skin turgor (hydrostatic pressure)

weight loss

altered level of consciousness

hypotension, tachycardia, weak and thready pulse, flat jugular veins

oliguria

sunken fontanelles (in babes)

Electrolyte Balance

￭Crucial role in homeostasis

￭Muscle and neural activity

￭Acid-base and fluid balance

Cations

positively charged electrolytes

Anions

negatively charged electrolytes

Electrolytes

Sodium+, Potassium+, Calcium+, Magnesium+, Chloride-

Sodium+

￭Extracellular fluid (ECF): neurological function; regulates fluid volume

￭Kidney reabsorbs

Potassium

￭Intracellular fluid (ICF): muscle contraction; cardiac conduction

￭Kidneys eliminate

Calcium +

￭Bone health; neuromuscular function; cardiac function

￭Insufficiency leads to osteoporosis

Magnesium

￭ICF; bone; many cellular functions

￭Alcoholism leads to low levels

Chloride

￭ECF; bound to other ions

￭Essential for HCL production

Sodium

⚬Plays a role in acid-base balance

⚬Facilitates muscles and nerve impulses through the sodium-potassium pump

⚬Main source is dietary intake

Normal Sodium Range

135-145 mEq/L

Hypernatremia Causes

SODIUM >145 mEq/L)

Excessive sodium (dietary sodium, hypertonic IV saline, Cushing's syndrome, corticosteroid use)

Deficient water (insufficient intake, third spacing, excessive output, prolonged hyperventilation, diuretic use, diabetes insipidus)

Hypernatremia Manifestations

symptoms of dehydration (increased temperature, warm and flushed skin, dry and sticky mucous membranes,) increased thirst, irritability, agitation, weakness, headache, seizures, lethargy, coma, blood pressure changes, tachycardia, weak and thready pulse, edema, decreased urine output

FRIED SALT (Hypernatremia acronym)

F-Fever, flushed skin

R- Restlessness, irritability

I- Increased fluid retention and blood

pressure

E- Edema (peripheral and pitting)

D- Decreased urine output, dry mouth

S- Skin flushed

A- Agitation

L- Low-grade fever

T- Thirst

Hyponatremia causes

SODIUM

Hyponatremia Manifestations

anorexia, gastrointestinal upset, dry mucous membranes, blood pressure changes, pulse changes, edema, headache, lethargy, confusion, diminished deep tendon reflexes, muscle weakness, seizures, and coma

SALT LOSS (Hyponatremia Acronym)

S- Seizures

A- Abdominal cramping

L- Lethargy

T- Tendon reflexes diminished

L- Loss of urine and appetite

O- Orthostatic Hypotension

S- Shallow respirations

S- Spasms of muscles

Potassium

The primary intracellular cation

Excreted through the kidneys and gastrointestinal tract

Plays a role in electrical conduction (nervous, musculoskeletal, cardiovascular), acid-base balance, and metabolism

Main source is dietary intake

Serum potassium cannot fluctuate much without causing serious issue!

NORMAL RANGE:

3.5-5 mEq/L

Hyperkalemia manifestations

POTASSIUM >5 mEq/L)

paresthesia, muscle weakness, flaccid paralysis, bradycardia, dysrhythmias, EKG changes, cardiac arrest, respiratory depression, abdominal cramping, nausea, and diarrhea

Hyperkalemia causes

Excretion- renal failure, Addison's disease, certain medications, and Gordon's syndrome,

Intake- oral potassium supplements, salt substitutes, and rapid intravenous administration of diluted potassium Increased release from cells: acidosis, blood transfusions, and burns or any other cellular injuries

MURDER (Hyperkalemia Acronym)

M- muscle weakness

U- urine (oliguria/ anuria)

R- respiratory distress

D- decreased cardiac contractility

E- ECG changes

R- reflexes

Hypokalemia Causes

POTASSIUM

Hypokalemia Manifestations

muscle weakness, paresthesia, hyporeflexia, leg cramps, weak and irregular pulse, hypotension, dysrhythmias, electrocardiogram changes, decreased bowel sounds, abdominal distension, constipation, ileus, and cardiac arrest

SIC WALT (Hypokalemia acronym)

S- Stomach issues (constipation, distension)

I- irritability

C- confusion

W- weakness

A- arrhythmias

L- light reflexes (hyporeflexia)

T- thready pulse

Calcium

Mostly found in the bone and teeth

Has synergistic relationship with magnesium

Plays a role in blood clotting, hormone secretion, receptor functions, nerve transmission, and muscular contraction

Main source is dietary intake (vitamin D aids absorption)

Has inverse relationship with phosphorus

Regulated by vitamin K, parathyroid hormone, and calcitonin

Calcium normal range

4-5 mEq/L

Hypercalcemia Causes

Increased intake or release: calcium antacids, calcium supplements, cancer, immobilization, corticosteroids, vitamin D deficiency, and hypophosphatemia

Calcium >5 mEq/L

Hypercalcemia Manifestations

GI symptoms (pain, N/V), bone pain, kidney stones, fatigue, malaise, constipation, polyuria, polydipsia, lethargy, confusion, depression, memory loss

Hypocalcemia Causes

Calcium

Hypocalcemia Manifestations

seizures, tetany (involuntary muscle contractions), paresthesias (burning, prickling sensation), anxiety, depression, ventricular tachycardia that could be fatal, positive Trousseau's and Chvostek's signs

Trousseau sign

Occlusion of arterial blood flow elicits carpal spasm

Chvostek sign

Tapping patient's facial nerve prompts brief facial spasm

Hypercalcemia Manifestations Acronym

Stones: kidney stones

Bones: bone pain

Groans: GI symptoms/pain, constipation

Moans: lethargy, fatigue, confusion, memory loss, depression

Thrones: polyuria, polydipsia

Hypocalcemia Manifestations Acronym

P- parasthias, positive truseaus/chvosteks

A- arrhythmias, anxiety

T- tetany

S- seizures, convulsions