2. Fluids and Electrolytes
Chapter 20
Fluids and Electrolytes
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Topics
Physiology of Fluid and Electrolyte Balance
Dehydration and Edema
Electrolyte Imbalances
Acidosis and Alkalosis
Herbal and Alternative Therapies
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4. 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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5. 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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6. 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
liters (L)
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7. 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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8. 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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9. Physiology of Fluid and Electrolyte Balance
Daily Fluid Balance
milliliters (mL)
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10. 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
milliequivalents (mEq)
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11. 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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12. 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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13. 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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14. 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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15. 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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16. 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
intravenous (IV)
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17. 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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18. 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)
intravenous (IV)
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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
congestive heart failure (CHF)
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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
milliosmoles (mOsm)
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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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30. 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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31. 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, salt- wasting 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
antidiuretic hormone (ADH)
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32. 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
blood pressure (BP)
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33. 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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34. 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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35. 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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36. 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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37. 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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38. 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
over-the-counter (OTC)
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39. 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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40. 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 products; use correct order of mixing
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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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42. 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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43. 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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44. 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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45. 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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46. 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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