Electrolytes and Fluid Balance Quiz

Fluid and Electrolyte Balance

• Electrolytes are salts, acids, bases, and some proteins
• Electrolyte balance often refers only to salt balance
• Salts control fluid movement, provide minerals for excitability, and are related to secretory activity and membrane permeability
• Salts enter the body through ingestion and metabolism
• Salts are lost through perspiration, feces, urine, and vomit

Composition of Body Fluids

• Water is the universal solvent in body fluids
• Solutes are classified as nonelectrolytes and electrolytes
• Body fluids contain electrolytes, which dissociate into ions in water
• Examples of electrolytes include inorganic salts, acids, bases, and some proteins
• Ions conduct electrical current
• Electrolytes have greater osmotic power than nonelectrolytes and cause fluid shifts

Altered Sodium Balance: Hyponatremia

• Serum sodium level < 135 mEq/L
• Causes include vomiting, diarrhea, and sweating
• Manifestations are related to plasma hypoosmolality and cellular swelling
• Symptoms include muscle twitching, weakness, hypotension, tachycardia, oliguria, anuria, and altered neuronal function (nausea, vomiting, lethargy)

Altered Sodium Balance: Hypernatremia

• Serum sodium > 145 mEq/L
• Causes include excessive dietary sodium intake and loss of body water
• Manifestations include intracellular dehydration (water movement from ICF to ECF), agitation, restlessness, decreased level of consciousness, hypertension, tachycardia, edema, and weight gain

Altered Potassium Balance: Hypokalemia

• Potassium level < 3.5 mEq/L
• Causes include reduced intake, increased loss due to diuretics, severe vomiting, and diarrhea
• Manifestations include membrane hyperpolarization (decreased neuromuscular excitability), cardiac arrhythmias, dizziness, hypotension, skeletal muscle weakness, and smooth muscle atony (nausea, anorexia, abdominal distension)

Altered Potassium Balance: Hyperkalemia

• Potassium level > 5 mEq/L
• Causes include iatrogenic (inappropriate drug use), shift of K+ from ICF to ECF, and decreased renal excretion
• Manifestations include membrane depolarization (increased neuromuscular excitability), cardiac arrest, abdominal cramping, and flaccid paralysis (reduced muscle tone)

Altered Calcium Balance: Hypocalcemia

• Calcium level < 4.5 mEq/L
• Causes include medications (heparin/glucagon), severe burns, kidney failure, thyroid disorder, vitamin D deficiency, and sepsis
• Manifestations include anxiety, increased excitability and muscle tetany, muscle twitch, spasm, cardiac arrhythmia, and hypotension

Altered Calcium Balance: Hypercalcemia

• Calcium level > 5.2 mEq/L
• Causes include excessive bone breakdown, thyroid disease, excessive calcium supplements intake, and excessive calcium-containing antacids
• Manifestations include decreased neuromuscular irritability (inhibits neurons and muscle cells), confusion, headaches, irritability, constipation, nausea, vomiting, heart arrhythmias, and muscle weakness

Altered Chlorine Balance: Hypochloremia

• Chlorine level < 98 mEq/L
• Often associated with hyponatremia, hypokalemia, and metabolic alkalosis
• Causes include vomiting, diarrhea, and diuretics
• Manifestations include excessive tone of muscle, tetany, weakness, twitching, shallow, depressed breathing, paralysis, and mental confusion

Altered Chlorine Balance: Hyperchloremia

• Chlorine level > 108 mEq/L
• Causes include severe dehydration, kidney failure, hemodialysis, and traumatic brain injury
• Manifestations include hyperchloremic metabolic acidosis, deep rapid breathing, headache, diminished cognitive ability, and cardiac arrest

Altered Magnesium Balance: Hypomagnesemia

• Magnesium level < 1.5mEq/L
• Associated with hypokalemia and hypocalcemia
• Causes include malnutrition, malabsorption, severe burns, alcoholism, and diuretic use
• Manifestations include tetany, muscle cramps, seizures, altered neuromuscular transmission, cardiac arrhythmia, and hypotension

Altered Magnesium Balance: Hypermagnesemia

• Magnesium level > 2.5mEq/L
• Less frequent than hypomagnesemia
• Causes include excessive intake of magnesium supplements, magnesium antacids, and end-stage renal disease
• Manifestations include reduced neuromuscular transmission and cell excitability, diminished reflexes, muscle weakness, and hypotension

Altered Phosphate Balance: Hypophosphatemia

• Phosphate level < 1.6 mEq/L
• Often associated with hypomagnesemia and hypokalemia
• Causes include severe burns, malnutrition, malabsorption, vitamin D deficiency, alcoholism, kidney disease, and prolonged diuretic use
• Manifestations include osteomalacia (soft bones), bone deformities, muscle weakness, tremor, and paresthesia (tingling, burning)

Altered Phosphate Balance: Hyperphosphatemia

• Phosphate level > 2.9 mEq/L
• Associated with hypocalcemia (reciprocal changes)
• Causes include fractures, bone disease, hypoparathyroidism, acromegaly, systemic infection, intestinal obstruction, and major tissue trauma
• Manifestations include no associated manifestations

Fluid Compartments

• Total body water is 60% of body weight (40 L in a 70 kg male)
• Two main compartments are intracellular fluid (ICF) and extracellular fluid (ECF)
• ICF comprises 40% of total body water, found inside cells
• ECF comprises 20% of total body water, outside cells and includes plasma (~5%), interstitial fluid (~14%), and transcellular fluid (~1%)

Fluid Movement Among Compartments

• Fluid exchange and mixing are continuous
• Movement is along osmotic gradients
• All body fluid osmolality is almost always equal
• Changes in solute concentration (any compartment) lead to net water flow

Fluid Regulation Cycle

• The cycle involves the hypothalamus, kidneys, and other organs
• ADH (antidiuretic hormone) is produced in response to changes in blood volume or osmolarity. ADH leads to water retention or excretion as needed
• In response to changes in blood pressure, the kidneys produce renin, regulating blood pressure and water balance. Hormones such as aldosterone, promote sodium retention or excretion

Diuretics

• Drugs that increase urine production to adjust fluid balance
• Types of diuretics include loop diuretics, thiazide diuretics, and potassium-sparing diuretics
• Each type targets a different segment of the nephron to promote fluid excretion

Disorders of Water Balance

• Categorized as total volume, concentration, or fluid distribution imbalances
• Disorders include fluid deficiency (negative balance), fluid excess (positive balance), and fluid sequestration (edema formation)

Hypovolemia (Fluid Deficiency)

• Deficit of body fluid volume
• Causes include excessive body fluid loss, reduction in fluid intake, loss of fluid due to a third space, or hemorrhage
• Manifestations include thirst, dry mucous membranes, weight loss, flattened neck veins, diminished skin turgor, prolonged capillary refill, decreased urine output, increased heart rate, decreased blood pressure, and altered level of consciousness

Dehydration (Fluid Deficiency)

• Negative fluid balance; body eliminates significantly more water than sodium
• ECF osmolality rises due to water loss through profuse sweating, water deprivation, diuretic abuse, endocrine disturbances (diabetes mellitus, ADH hyposecretion), or diabetes insipidus
• Dehydration affects all water compartments
• Clinical signs include skin turgor loss, sticky oral mucosa, thirst, dry flushed skin, and low urine output

Hypervolemia (Fluid Excess)

• Expansion of extracellular fluid, involving interstitial or vascular space
• Causes include heart failure, cirrhosis, kidney failure, excessive fluid replacement, and administration of osmotically active fluids
• Manifestations include increased blood pressure, increased sodium and water excretion, heart failure, and pulmonary edema

Hypotonic Hydration (Fluid Excess)

• Cellular overhydration (water intoxication)
• More water than sodium is retained or rapid, excess water ingestion
• Occurs after periods of strenuous activity, or excessive water intake without electrolyte replenishment which leads to a decrease in ECF osmolality and net osmosis of water into tissue cells
• Manifestations include swelling of the cells, severe metabolic disturbances (nausea, vomiting, muscular cramping, cerebral edema), possible death

Fluid Sequestration (Edema)

• Atypical accumulation of fluid in interstitial space
• Causes include increased fluid out of blood, decreased fluid into blood, (increased capillary hydrostatic pressure, decreased capillary oncotic pressure, increased capillary permeability, and lymphatic obstruction)
• Edema can result in impaired function in joints, organs like brain and lungs, and extremities like arms and legs