Chapter 20
Fluids and Electrolytes
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Chapter 20
Topics
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Physiology of Fluid and Electrolyte Balance
Dehydration and Edema
Electrolyte Imbalances
Acidosis and Alkalosis
Herbal and Alternative Therapies
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Physiology of Fluid and Electrolyte Balance
Fluids and Electrolyte Balance
• Fluids and electrolytes depend on each other; a change in
one component causes a change to the other
• Electrolytes are solutes (salts and minerals) that dissolve in
a solvent, usually water
• Water moves from areas of low solute concentration to
areas of high solute concentration to maintain equilibrium
• A loss of fluids in an area of the body causes a shift in
fluids from another area to replace what was lost
 During fluid shifts, electrolytes exchange to balance the
solute concentration between fluid compartments
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Physiology of Fluid and Electrolyte Balance
Fluids
• Two-thirds of body fluid is intracellular fluid (inside the
cellular membrane); volume is constant
• One-third of body fluid is extracellular fluid (outside of
cells); volume varies; contains most substances that
maintain proper solute concentrations
 75% of extracellular fluid is in the interstitial spaces
between the cells in tissues
 25% is in the plasma inside blood vessels
• Extracellular fluid helps maintain the overall fluid balance
and hydration status of the body
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Physiology of Fluid and Electrolyte Balance
Body Fluid
Compartments
• Extracellular fluid
is made up of
plasma and
interstitial fluid
• Average quantities
of water are given
in liters (L) for
each body
compartment
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Physiology of Fluid and Electrolyte Balance
Fluids (continued)
• Water is the main fluid in the body
 Crucial for dissolving essential substances and
transporting these molecules throughout the body
 Water content changes with age and body makeup
• Homeostasis involves proper fluid balance
 Multiple systems regulate water intake and output;
distribute water into the various body compartments
• Typically, water intake roughly matches output
 Adults take in 2 L of water a day via fluids and food
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Physiology of Fluid and Electrolyte Balance
Body Water
Content
• In infants,
water is
70–80% of the
body by weight
• In the elderly,
water content
is much lower
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Physiology of Fluid and Electrolyte Balance
Daily Fluid Balance
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Physiology of Fluid and Electrolyte Balance
Electrolytes
• Molecular compounds that form ions dissolved in water
• They are either positively charged ions (cations) or
negatively charged ions (anions)
 Cations: sodium, potassium, calcium, magnesium
 Anions: chloride, bicarbonate, phosphate (at times)
• Concentration is measured in milliequivalents (mEq)
per liter
• Concentrations of ions differ in intracellular and
extracellular fluid
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Physiology of Fluid and Electrolyte Balance
Electrolytes (continued)
• Pumps (e.g., sodium/potassium ion) and channels (e.g.,
chloride) maintain concentrations in cell membranes
• Water passively moves across cell membranes by osmosis
 Maintains overall equilibrium in concentration of total
molecules on both sides
• Concentration of intracellular and extracellular fluid
typically remains constant
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Physiology of Fluid and Electrolyte Balance
Common Electrolytes: Sodium (Na+ )
• Most abundant cation in extracellular fluid
• Sodium retains body fluid, helps generate and transmit
nerve impulses, maintains acid-balance balance, regulates
enzyme activity
• The main active ion in maintaining fluid isotonicity
 Isotonicity is a state of balanced concentration across
cell membranes
• Normal Concentration: 136–145 mEq/L
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Physiology of Fluid and Electrolyte Balance
Common Electrolytes: Potassium (K+)
• The primary cation in intracellular fluid
• Potassium helps generate and conduct nerve impulses and
muscle contractions (such as in cardiac function and
rhythm), maintains acid-base balance, regulates enzyme
activity, is involved in carbohydrate metabolism
• Normal Concentration: 3.5–5.5 mEq/L
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Physiology of Fluid and Electrolyte Balance
Common Electrolytes: Calcium (Ca2+)
• Calcium is essential for bone formation, muscle
contraction, conduction of nerve impulses, blood
coagulation
• Electrolyte is highly bound to albumin (plasma protein);
low albumin levels can result in hypocalcemia
• Normal Concentration: 4.3–5.3 mEq/L
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Physiology of Fluid and Electrolyte Balance
Common Electrolytes: Magnesium (Mg2+)
• An abundant intracellular cation
• Magnesium activates enzymes and facilitates nerve
impulse production and muscle contraction
• Electrolyte is important to cardiac function
• Normal Concentration: 1.5–2.5 mEq/L
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Physiology of Fluid and Electrolyte Balance
Common Electrolytes: Chloride (Cl-)
• An anion that transports carbon dioxide, forms
hydrochloric acid in the stomach, and retains potassium
• Chloride controls acid–base balance
• Normal Concentration: 100–106 mEq/L
Common Electrolytes: Bicarbonate (HCO3-)
• An anion that helps to maintain blood pH
• Its most common salt form, sodium bicarbonate, used in
IV preparations to treat acidosis
• Normal Concentration: 27 mEq/L
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Physiology of Fluid and Electrolyte Balance
Common Electrolytes: Phosphate (PO4-)
• Anion used in energy production for normal cell function
• Phosphate counterbalances calcium in blood
• Excessive intake of electrolyte can deplete calcium levels,
affecting bone health
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Physiology of Fluid and Electrolyte Balance
Acid-Base Balance
• Electrolytes affect balance of hydrogen ions (H+) in blood
• The concentration of hydrogen ions is the pH scale
 Low pH is acidic; high pH is alkaline
• pH of blood is between 7.35 and 7.45
 The acid–base buffer pair of carbonic acid (acid) and
sodium bicarbonate (base) keep pH in this range
• Kidneys and lungs also maintain acid-base balance
 Kidneys regulate electrolytes in the urine
 Respiratory rate (breathing faster or slower) can correct
pH imbalance
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Dehydration and Edema
Dehydration
• Excessive loss of water mainly from extracellular
compartments
• Causes: vomiting, diarrhea, sweating from heat or fever,
excessive urine output
• Symptoms: thirst, dry mucous membranes, weakness,
dizziness, reduced skin elasticity (turgor), hypotension,
rapid heartbeat, reduced or absent urine production
• Treatment: drinking fluids (mild dehydration); IV fluids and
electrolytes (moderate to severe dehydration)
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Dehydration and Edema
Edema
• Accumulation of excessive fluid in interstitial space
• Most common in lower extremities, lungs, brain
• Causes: sodium and fluid retention in extracellular space,
renal failure, reduced tissue perfusion from CHF
• Symptoms: swelling in ankles or legs, difficulty breathing
• Treatment: diuretics to remove excessive fluid through
elimination and correct electrolyte imbalances
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Your Turn
Question 1: Sodium and potassium are two cations in the human
body. How are they alike?
Answer: They both help generate and transmit nerve
impulses, assist with acid–base balance, and regulate
enzyme activity.
Question 2: A patient is diagnosed with severe dehydration.
What is the physician likely to order?
Answer: The physician is likely to order administration of IV
fluids and electrolytes.
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Dehydration and Edema
Fluids and Solutions
• Three main uses of IV fluid products
 Replace lost fluids and electrolytes due to dehydration
 Supply essential trace minerals in parenteral nutrition
solutions
 Serve as vehicle for administration of IV drug therapy
• IV fluids are categorized by
 Tonicity (isotonic, hypertonic, hypotonic)
 Content (colloids versus crystalloids)
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Dehydration and Edema
Fluids and Solutions: Tonicity
• Tonicity refers to the concentration of a solute (dissolved
substance) in a solvent (liquid vehicle)
• Concept of tonicity applies to molecules such as ions and
electrolytes that do not move easily across cell membranes
• IV electrolyte products are used and prepared based on
their tonicity (concentration compared with that of blood)
• Osmolarity: concentration of all molecules in a set volume
of fluid; measurement affects tonicity
 Measured in milliosmoles (mOsm) per liter (L)
 Plasma osmolarity is about 280–300 mOsm/L
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Dehydration and Edema
Fluids and Solutions: Isotonic Solutions
• Isotonic solutions (or maintenance solutions) have similar
concentration as blood plasma
• Indication: replace daily fluid and electrolyte loss, prevent
dehydration
• Most common isotonic solution: normal saline (0.9% NaCl)
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Dehydration and Edema
Fluids and Solutions: Hypertonic Solutions
• Hypertonic solutions have a higher concentration of solute
than bodily fluids; osmolarity is usually over 350 mOsm/L
• Indication: severe sodium depletion from excess sweating,
vomiting, or diarrhea; excessive water intake; overuse of
enemas or irrigating solutions
• Cautions: administer through a central IV line due to their
irritating and corrosive effects on tissues and blood
vessels; must be given slowly and monitored closely
 Rapid delivery can damage tissues and lead to fluid
overload in blood vessels; heart failure may result
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Dehydration and Edema
Fluids and Solutions: Hypotonic Solutions
• Hypotonic (hydrating) solutions have lower concentration
of solute than bodily fluids; osmolarity is usually less than
280 Osm/L
• Indication: dehydration by diluting the concentration
within the bloodstream
 This decreases osmolarity (water leaves the blood and
enters interstitial and intracellular spaces)
• Caution: Too rapid administration of solution can cause
intracranial pressure and brain damage
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Dehydration and Edema
Tonicity Effects on
Cells in Solution
• Body cells can be
bathed with isotonic
solution without a
net change between
intracellular and
extracellular
concentrations
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Dehydration and Edema
Fluids and Solutions: Crystalloid IV Solutions
• Crystalloid IV solutions contain electrolytes and colloids
(proteins and other large molecules such as fats)
• Molecules in colloid products are too large to easily move
from the bloodstream to surrounding tissues
• Like hypertonic solutions, they increase osmolarity of
blood plasma by pulling fluid from interstitial spaces
• Colloid products often called blood volume expanders
 Examples of colloids: albumin, dextran, blood
• Indication : replace lost fluid and treat dehydration; serve
as a liquid vehicle to administer IV drugs
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Dehydration and Edema
Fluids and Solutions: Crystalloid IV Solutions
(continued)
• Normal saline (0.9% NaCl)and dextrose 5% in sterile water
(D5W) are isotonic crystalloid solutions
 Dextrose used for malnutrition or low glucose levels
• See Table 20.2 for common crystalloid solutions and their
osmolarity
• Special Caution: use sterile water only for diluting other IV
drugs or fluids; never administer it by itself
 Technicians: question any order for hydration therapy
containing pure water
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Electrolyte Imbalances
About Electrolyte Imbalances
• Causes: loss or excessive production of the electrolyte
itself or from a relative reduction or excess of fluid
• See Table 20.1 for normal electrolyte concentrations
• Measuring electrolyte concentration in plasma is close
estimate of extracellular levels
• Intracellular levels cannot be measured directly
 Lab values are combined with clinical signs and
symptoms to determine deficits
• Technicians can retrieve laboratory values and flag those
outside of normal range
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Electrolyte Imbalances
Electrolyte Imbalances: Sodium
• Hyponatremia is low sodium concentration from sodium
loss or a relative excess of water in extracellular space
 Causes: high water intake, kidney or liver failure, saltwasting diuretics overuse, adrenal gland insufficiency
 Causes (other): fluid loss caused by excessive vomiting
or sweating
• Hypernatremia is elevated sodium concentration
 Causes: dehydration from lack of fluid intake, diarrhea,
ADH deficiency, heart disease, kidney failure
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Electrolyte Imbalances
Electrolyte Imbalances: Potassium
• Hypokalemia is low potassium concentration
 Causes: overuse of potassium-wasting diuretics,
vomiting or gastric suctioning, or excessive urine output
 Symptoms: reduced muscle tone, weakness, confusion,
drowsiness, depression, low BP, cardiac arrhythmias
• Hyperkalemia is elevated potassium; severely affects heart
 Causes: kidney failure, diarrhea, potassium-sparing
diuretics overuse, Cushing’s syndrome, severe burns
 Symptoms: depressed breathing, diarrhea, nausea,
vomiting, confusion, anxiety, cardiac arrhythmias
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Electrolyte Imbalances
Electrolyte Imbalances: Calcium
• Hypocalcemia is low calcium levels in the body
 Causes: insufficient calcium intake, parathyroid disease
 Symptoms: hyperexcitability of nerves and muscle
contraction, muscle spasms, seizures
 Death may result
• Hypercalcemia is elevated calcium concentration
 Causes: excessive intake of calcium supplements, some
cancerous tumors
 Symptoms: kidney stones
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Electrolyte Imbalances
Electrolyte Imbalances: Magnesium
• Hypomagnesemia is low levels of magnesium in the body
 Causes: alcohol abuse, pregnancy-induced
hypertension, drugs causing increased magnesium
excretion (digoxin, estrogen, diuretics)
 Symptoms: muscle cramps, confusion, tachycardia,
arrhythmias, tremors, hallucinations, seizures
• Hypermagnesemia is elevated magnesium concentration
 Causes: renal failure, IV infusion overdose, enemas
 Symptoms: reduced deep tendon reflexes, changes in
cardiac function
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Electrolyte Imbalances
Electrolyte Imbalances: Chloride
• Hypochloremia is low levels of chloride in the body
 Causes: loss of fluid from excessive production of urine
or sweat, gastric suctioning, some diuretics
• Hyperchloremia is elevated chloride concentration
 Causes: diarrhea, kidney disease, diabetes
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Electrolyte Imbalances
Electrolyte Imbalances: Phosphate
• Hypophosphatemia is low levels of phosphate in the
bloodstream
 Causes: anorexia, severe malnutrition, kidney failure
 Symptoms: weakness, respiratory or heart failure,
hemolysis, rhabdomyolysis
• Hyperphosphatemia is elevated phosphate concentration
 Causes: tumor lysis syndrome, rhabdomyolysis, lactic
acidosis, diabetic ketoacidosis, bisphosphonates, too
much vitamin D, overuse of bowel prep products
 Symptoms: kidney damage or failure
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Electrolyte Imbalances
Electrolytes
• Indication: electrolyte deficiency, or if anticipated
• Electrolytes in body fluids can be replaced in various ways
• Parenteral nutrition: electrolyte solutions combined with
carbohydrates, proteins, and fats in large-volume bags
 Infused through an IV line
• If mild depletion, replace by including the absent mineral
in the diet or taking an oral supplement
 For example, athletes consuming sports drinks
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Electrolyte Imbalances
Electrolytes (continued)
• Oral OTC liquid electrolyte mixtures treat mild
dehydration from vomiting or diarrhea
 Safe to use; contain small amounts of electrolytes
• IV electrolyte products are used for severe deficiencies
 Electrolytes added to IV fluids and administered
• Oral potassium supplements for potassium loss (diuresis)
• Oral calcium products for prevention and treatment of
bone loss from osteoporosis, rickets; also used for tetany
• Oral magnesium products for magnesium loss
• Phosphorus products for malnourishment
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Electrolyte Imbalances
Electrolytes: Common Side Effects
• Sodium: water retention, high blood pressure
• Potassium: nausea, vomiting, diarrhea, abdominal pain,
GI ulceration (severe)
• Calcium: constipation; back or flank pain, painful urination,
nausea and vomiting (symptoms of kidney stones)
• Magnesium: diarrhea
• Phosphorus: stomach upset; diarrhea; back or flank pain,
painful urination, nausea and vomiting (symptoms of
kidney stones)
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Electrolyte Imbalances
Electrolytes: Cautions
• Do not use most electrolyte products if have kidney failure
or impairment
• Dilute injectable potassium products before administering
 Maximum safe concentration is 80 mEq/L
 Administer infusion slowly; if too fast, could cause
cardiac arrest (black tops to remind technicians)
• Calcium and phosphate salts cannot always be mixed in
the same IV bags; they can chelate
 Precipitate appears as small white specks or lumps of
material; can clog capillaries if infused through an IV
 Technicians: follow
accepted
procedures to mix these 40
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Your Turn
Question 1: What is the reason isotonic solutions are known as
maintenance solutions?
Answer: Isotonic solutions have the same concentration as
blood. They are used to maintain fluid status in normal
range.
Question 2: What is a restriction of using electrolyte products?
Answer: Most electrolyte products cannot be used in
patients with kidney failure or impairment.
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Acidosis and Alkalosis
About Acidosis
• Condition occurs when extracellular fluid (blood) contains
excess hydrogen ions, causing the pH to drop below
normal range
• Metabolic acidosis: excess acid is produced and
bicarbonate is lost (e.g., diarrhea), or kidneys do not
excrete enough acid
• Respiratory acidosis: slow breathing and retention of
carbon dioxide in the blood
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Acidosis and Alkalosis
About Alkalosis
• Condition caused by a loss in hydrogen ions, producing a
relative increase in bicarbonate; this increases blood pH
• Metabolic alkalosis: excess acid excreted by kidneys or acid
is lost from the stomach (from vomiting or gastric suction)
• Respiratory alkalosis: rapid breathing and elimination of
carbon dioxide from the blood
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Acidosis and Alkalosis
Acidifying and Alkalinizing Agents
• Acidic electrolyte products treat alkalosis; basic products
treat acidosis
• Ammonium chloride (acidic) treats hypochloremia and
metabolic alkalosis
 Can result in ammonium toxicity; monitor patient
• Sodium bicarbonate (basic) used as an antacid and
as a urinary alkalinizer for hemolytic emergencies;
also used to treat metabolic acidosis and drug overdoses
 Can result in sodium toxicity, causing fluid overload
 Can cause ulceration of tissue at injection site
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Acidosis and Alkalosis
Acidifying and Alkalinizing Agents (continued)
• Cautions:
 Technician must carefully mix and label these agents
 Concentrations and rates of infusion must be
precise to avoid adverse effects
 Healthcare providers need to be attentive to signs of
extravasation
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Herbal and Alternative Therapies
• Electrolytes often categorized as dietary supplements
rather than OTC or prescription drug products
• Many electrolyte drinks are available for rehydration
 Use after physical exercise
 Use to treat diarrhea and vomiting associated with
intestinal illness
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Summary
• Common electrolytes in the body are sodium, potassium,
calcium, magnesium, phosphate, and chloride
• Excess or loss of a common ion can cause major illness
• Various types of IV fluids and electrolyte products are
used to prevent and treat imbalances
• Some IV fluid products are used as delivery vehicles for IV
drug therapy
• IV electrolyte solutions containing ammonium chloride
and sodium bicarbonate are used for acid–base disorders
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