Electrolytes

Fluid & Electrolyte Imbalances

Objectives

• Discuss the following key topics:
  1. Homeostasis
  2. Fluid compartments
  3. Electrolytes

• Explain the role of the following electrolytes in body maintenance and the typical serum range for each:

  • Na+ (sodium)

  • K+ (potassium)

  • Ca++ (calcium)

  • Magnesium

  • Phosphate

• Identify health assessment, laboratory, and diagnostic findings associated with fluid and electrolyte imbalances.

• Differentiate the causes, physiology, signs and symptoms, complications, & medical management and nursing care of individuals experiencing the following fluid and electrolyte imbalances:

  • Hypernatremia and hyponatremia

  • Hyperkalemia and hypokalemia

  • Hypercalcemia and hypocalcemia

  • Hyperphosphatemia and hypophosphatemia

  • Hypermagnesemia and hypomagnesemia

Homeostasis

• Body fluids and electrolytes play a crucial role in maintaining homeostasis, which refers to the body’s stable internal environment.

• Body fluids are in continuous motion, performing essential functions such as:

  • Transporting nutrients

  • Carrying electrolytes

  • Delivering oxygen

  • Carrying waste products

• Various diseases and their treatments can significantly affect fluid and electrolyte balance. It is essential for healthcare professionals to:

  • Anticipate potential imbalances associated with certain disorders and medical therapies.

  • Recognize the signs and symptoms of imbalances.

  • Intervene with appropriate actions.

Water Content of the Body

• The body is primarily composed of water, with its percentage varying based on factors including body mass, gender, and age:

  • Preterm infants: 75% to 80%

  • Neonates: 70% to 75%

  • Children: 60% to 65%

  • Adults: 50% to 60% of body weight

  • Older adults: 45% to 50% of body weight

• Older adults have a higher risk for fluid-related problems compared to younger adults.

Body Fluid Compartments

• The body contains two primary fluid compartments:

  • Intracellular Space:

  • Contains 2/3 of body water within cells.

  • Known as intracellular fluid (ICF).

  • Extracellular Space:

  • Contains 1/3 of body water outside the cells.

  • Composed of two components:

    • Interstitial Fluid: Fluid in spaces between the cells.

    • Intravascular Fluid: Plasma, the liquid part of the blood.

Fluid Distribution of Young Adult Male

• Total distribution in a young adult male includes:

  • Plasma: 3 L

  • Interstitial Fluid: 10 L

  • Intracellular Fluid (ICF): 28 L

Electrolytes

• Definition: Electrolytes are substances whose molecules dissociate into ions when dissolved in water; ions are electrically charged particles.

Types of Ions

• Cations (positively charged ions):

  • Sodium (Na+)

  • Potassium (K+)

  • Calcium (Ca²+)

  • Magnesium (Mg²+)

• Anions (negatively charged ions):

  • Bicarbonate (HCO₃¯)

  • Chloride (Cl¯)

  • Phosphate (PO₄³¯)

  • Most proteins

Electrolyte Reference Intervals

• Normal serum electrolyte values are as follows:

  • Sodium (Na+): 135-145 mEq/L

  • Potassium (K+): 3.5-5.0 mEq/L

  • Calcium (Ca²+): 9.0-10.5 mg/dL

  • Magnesium (Mg²+): 1.3-2.1 mEq/L

  • Phosphate (PO₄³¯): 2.5-4.5 mg/dL

Terminology to Know

• Diffusion: Movement of molecules from an area of higher concentration to an area of lower concentration.

• Facilitated Diffusion: Process of passive transport involving integral membrane proteins.

• Active Transport: Movement against a concentration gradient requiring energy.

• Osmosis: Movement of water across a selectively permeable membrane.

• Osmotic Pressure: Pressure required to prevent osmotic movement across a semipermeable membrane.

  • Osmolarity: Concentration of solute particles in a solution.

  • Osmolality: Concentration of solute per kilogram of solvent.

• Isotonic, Hypotonic, Hypertonic: Relative solute concentrations compared between two solutions.

• Hydrostatic Pressure: The pressure exerted by a fluid at equilibrium due to the force of gravity.

• Oncotic Pressure: The pressure exerted by proteins (albumin) in the blood plasma that pulls water into the bloodstream.

• Fluid Spacing: A term used to describe the distribution of body water:

  • First Spacing: Normal distribution of fluid between intracellular fluid (ICF) and extracellular fluid (ECF).

  • Second Spacing: Abnormal accumulation of fluid in the interstitial space (edema).

  • Third Spacing: Excess fluid collection in areas that do not readily re-enter interstitial space (e.g., ascites).

Regulation of Water Balance

• Daily water intake for an average adult is approximately 2000-3000 mL.

• Water intake is primarily through:

  • Fluids

  • Solid foods

  • Water produced from metabolic processes

• Losses occur through:

  • Urinary output

  • Feces

  • Insensible loss (from lungs and skin)

Nursing Management: Fluid Volume Imbalances

• Fluid Deficits (not the same as dehydration): ECF volume deficit (hypovolemia) results from shifting fluid from plasma to interstitial space. Common causes include:

  • Diarrhea

  • Vomiting

  • Hemorrhage

  • Polyuria

• Fluid Excess: ECF volume excess (hypervolemia) results from a shift of fluid from interstitial space into plasma. Common causes include:

  • Heart failure

  • Renal failure

• General Nursing Implementation:

  • Daily weights

  • Monitor intake and output

  • Assess laboratory findings

  • Monitor vital signs

  • Conduct cardiovascular and respiratory assessments

  • Perform integument assessments

  • Administer fluid therapy

  • Ensure patient safety

Sodium Function and Imbalance

• Normal Serum Sodium Levels: 135-145 mEq/L

• Role of Sodium:

  • Maintains concentration and volume of ECF

  • Influences water distribution between ECF and ICF

  • Generating and transmitting nerve impulses and muscle contractility

  • Regulating acid-base balance

• Sodium Absorption and Regulation:

  • Absorbed primarily in the GI tract; regulated by the kidneys, which excrete or retain sodium based on body fluid status and the influence of hormones (ADH and Aldosterone).

Hypernatremia (High Serum Sodium)

• Clinical Definition: Elevated serum sodium due to water loss or sodium gain.

  • Common states include inadequate water intake, excess water loss, or rare sodium gain.

• Pathophysiology:

  • ECF hyperosmolality results in cellular dehydration as water shifts out of the cells.

• Clinical Manifestations:

  • Thirst

  • Lethargy

  • Agitation

  • Seizures

  • Coma

  • Impaired level of consciousness (LOC)

  • Dry, swollen tongue

  • Postural hypotension

  • Weight loss

• Nursing Implementation:

  • Treat the underlying cause and assess volume status:

  • For primary water deficit, administer oral or IV isotonic solutions (e.g., 0.9% sodium chloride).

  • For sodium excess, dilute high sodium through sodium-free IV fluids (e.g., 5% dextrose).

  • Monitor sodium levels; serum Na levels should not decrease by more than 8 to 15 mEq/L in an 8-hour period.

Hyponatremia (Low Serum Sodium)

• Clinical Definition: Results from a loss of sodium-containing fluids or water excess in relation to sodium.

  • Causes include vomiting, diarrhea, NG suction, primary adrenal insufficiency, and inappropriate use of hypotonic IV fluids.

• Clinical Manifestations:

  • Headache

  • Irritability

  • Difficulty concentrating

  • Vomiting

  • Confusion

  • Seizures

  • Coma

• Nursing Implementation:

  • For mild hyponatremia (water excess), restrict fluid intake.

  • For acute and/or severe hyponatremia, small amounts of IV hypertonic saline solution (3% NaCl) can be administered; levels should not increase more than 10-12 mEq/L in the first 24 hours.

Potassium Function and Imbalance

• Normal Serum Potassium Levels: 3.5-5.0 mEq/L

• Role of Potassium:

  • Major ICF cation; essential for conducting nerve impulses and normal muscle function.

  • Involved in intracellular osmolality and cell growth, glycogen deposition, and acid-base balance.

• Hyperkalemia (High Serum Potassium):

  • Causes include massive intake, impaired renal excretion, shifts from ICF to ECF, potassium-containing drugs, and salt substitutes.

  • Commonly seen in renal failure.

  • Clinical Manifestations: Weak or paralyzed skeletal muscle; cardiac dysrhythmias, abdominal cramping, and diarrhea.

  • Nursing Management:

  • Eliminate oral and parenteral K intake, increase elimination (e.g., diuretics, dialysis).

  • Administer IV regular insulin with dextrose; monitor ECG.

• Hypokalemia (Low Serum Potassium):

  • Caused by abnormal losses (e.g., diarrhea, vomiting) or shifts from ECF to ICF.

  • Clinical Manifestations: Cardiac changes (flattened T waves, ST segment depression), weakness, respiratory muscle issues.

  • Nursing Management:

  • KCl supplementation (oral or IV) is crucial; observe for phlebitis and infiltration.

Calcium Function and Imbalance

• Normal Serum Calcium Levels: 9.0-10.5 mg/dL

• Role of Calcium: Major in bones and teeth; essential for blood clotting, nerve impulse transmission, myocardial contraction, and muscle contraction. Absorption requires Vitamin D.

• Hypercalcemia (High Serum Calcium):

  • Usually caused by hyperparathyroidism, cancers, or intake of excessive calcium.

  • Clinical Manifestations: Sedative-like effects leading to weakness, confusion, and increased blood pressure.

  • Nursing Management:

  • Interventions include stopping hypercalcemia-related medications, low-calcium diet, hydration, or IV saline for severe cases.

• Hypocalcemia (Low Serum Calcium):

  • Causes include decreased PTH production, blood transfusions, or vitamin D deficiency.

  • Clinical Manifestations: Increased nerve excitability, tetany, cardiovascular problems such as prolonged QT interval.

  • Nursing Management:

  • Provide diet high in calcium, IV calcium gluconate for symptomatic cases.

Phosphorus Function and Imbalance

• Normal Serum Phosphate Levels: 2.5-4.5 mg/dL

• Hyperphosphatemia:

  • Common in chronic kidney disease.

  • Clinical Manifestations: Tetany, muscle cramps.

  • Management: Restrict intake, administer phosphate binders, and consider dialysis for severe cases.

• Hypophosphatemia:

  • Results from decreased absorption or increased excretion.

  • Clinical Manifestations: Confusion, muscle weakness, respiratory failure.

  • Management: Oral phosphate supplements or IV sodium phosphate for severe cases.

Magnesium Function and Imbalance

• Normal Serum Magnesium Levels: 1.3-2.1 mEq/L

• Hypermagnesemia (High Serum Magnesium):

  • Causes: Increased magnesium intake, typically in renal impairment.

  • Symptoms: Hypotension, lethargy, urinary retention.

  • Management: Discontinue magnesium-containing drugs, provide fluids, and diuretics if indicated.

• Hypomagnesemia (Low Serum Magnesium):

  • Causes: Limited intake or excessive losses.

  • Symptoms: Confusion, muscle cramps, dysrhythmias.

  • Management: Oral supplements and IV magnesium sulfate for severe cases, with careful monitoring.

Important Considerations in Nursing Practice

• Monitor and evaluate fluid and electrolyte levels consistently during patient care, especially in older adults, as they have different physiological responses.

• Implement preventative measures to avoid volume imbalances during hospitalizations or in patients with chronic conditions such as heart failure.

Example Questions for Review

1. During postoperative care for an older adult patient, what should a nurse monitor closely to assess for fluid and electrolyte imbalances?

2. Identify findings indicating fluid volume deficit in a patient presenting with GI bleeding.

3. What nursing interventions should be implemented for a patient experiencing hyponatremia with fluid volume excess?

4. Following a parathyroidectomy, what manifestations should a nurse assess for in the patient?

5. For a patient on furosemide and digitalis, what potential complications should the nurse monitor for?

References

• Hagler, M.M.H.J.K. D. (2023). Lewis's Medical-Surgical Nursing: Assessment and Management of Clinical Problems (12th ed.). Elsevier Health Sciences (US). https://pageburstls.elsevier.com/books/9780323792332