Fluid and Electrolyte Imbalances in Nursing

Acknowledgement of Country

  • RMIT University pays respect to the Woi Wurrung and Boon Wurrung language groups of the Eastern Kulin Nation.
  • Recognizes ancestors and elders, acknowledging their continuous connection to the land.

Learning Objectives

  • Understanding fluid balance mechanisms in the body:
  • Regulation of fluid intake and output.
  • Disorders related to fluid imbalance.
  • Mechanisms regulating electrolyte balance in the body.
  • Causes, pathophysiology, and symptoms of electrolyte imbalances.

Fluid Compartments

  • Total Body Water: 40 L, 60% of body weight.
  • Extracellular Fluid (ECF): 15 L, 20% of body weight.
  • Plasma: 3 L (20% of ECF).
  • Intracellular Fluid (ICF): 25 L, 40% of body weight.
  • Interstitial Fluid (IF): 12 L, 80% of ECF.

Composition of Body Fluids

  • Water: Universal solvent.
  • Solutes: Classified as non-electrolytes (e.g., glucose) and electrolytes (e.g., Na+, Cl-).
  • Electrolytes have a greater osmotic power and influence fluid shifts.

Cellular Fluid Compartments

  • ECF: High in Na+ and Cl-, except plasma (higher protein content).
  • ICF: Low in Na+ and Cl-, high in K+ and phosphate (HPO4^2-).

Fluid Balance

  • Fluid Intake: 2600 mL total, derived from beverages (1300 mL), food (1000 mL), and metabolic processes (300 mL).
  • Fluid Loss: Mainly urine (60%), also through perspiration, feces, and insensible losses.

Water Losses

  • Conditions increasing fluid loss include burns, fever, vomiting, diarrhea, diuretics, diabetes mellitus, and kidney failure.

Regulation of Water Intake

  • Inhibitory feedback signals include dry mouth relief and activation of stretch receptors in the stomach/intestines.

Mechanisms of ADH Release

  • Increased osmolality and Na+ concentration stimulate osmoreceptors in the hypothalamus, leading to ADH release from the posterior pituitary:
  • Effects: Increased water reabsorption in kidneys, lowering osmolality, resulting in scant urine.

Disorders of Water Balance

  1. Dehydration: Negative fluid balance due to abnormal loss, with symptoms like dry skin, oliguria, confusion.
  2. Overhydration: Leads to hyponatremia, swelling of cells, and may cause severe metabolic disturbances.
  3. Edema: Accumulation of interstitial fluid causing tissue swelling, results from increased hydrostatic pressure or decreased oncotic pressure.

Electrolyte Balance

  • Electrolytes vital for:
  • Neuromuscular excitability,
  • Secretory activity,
  • Membrane permeability,
  • Fluid movement control.

Vital Electrolytes

  • Major ions include:
  • Sodium (Na+, ECF),
  • Potassium (K+, ICF; most abundant),
  • Calcium (Ca2+, ECF and bone),
  • Phosphate (HPO4^2-, ICF and bone),
  • Magnesium (Mg2+, ICF).

Sodium Balance

  • Normal levels: 135 – 145 mmol/L.
  • Regulates nerve action potentials and maintains body fluid volume.

Hypernatremia (>145 mmol/L)

  • Causes: Excess sodium intake or water loss (e.g., dehydration, diabetes insipidus).
  • Symptoms: Weakness, increased thirst, dry mouth, decreased urine output.

Hyponatremia (<135 mmol/L)

  • Causes: Excess water intake, diuretics, and hormonal imbalances.
  • Symptoms: Fatigue, muscle cramps, cold clammy skin, potential seizures.

Potassium Balance

  • Normal levels: 3.5 - 5.0 mmol/L.
  • Functions: Controls cell excitability and muscle contraction.

Hyperkalemia (>5.0 mmol/L)

  • Causes: Renal failure, excessive intake.
  • Symptoms: Muscle weakness, cardiac dysrhythmias.

Hypokalemia (<3.5 mmol/L)

  • Causes: Diuretics, diarrhea, low dietary intake.
  • Symptoms: Muscle weakness, respiratory distress, potential cardiac arrhythmias.

Calcium Balance

  • Normal levels: 2.15 – 2.55 mmol/L.
  • Regulates muscle contractions, blood clotting, hormone release.

Hypercalcemia (>2.55 mmol/L)

  • Causes: Excess dietary calcium, hyperparathyroidism.
  • Symptoms: Muscle weakness, confusion, kidney stones.

Hypocalcemia (<2.15 mmol/L)

  • Causes: Vitamin D deficiency, hypoparathyroidism.
  • Symptoms: Muscle spasms, cardiac arrhythmias.

Phosphate and Magnesium Balance

  • Phosphate levels: 0.78 - 1.42 mmol/L; regulated by PTH.
  • Magnesium levels: 0.75 – 1.25 mmol/L; essential for several metabolic activities.
  • Imbalances can cause similar symptoms to calcium imbalances, such as muscle weakness and arrhythmias.

Conclusion

  • Understanding mechanisms of fluid and electrolyte balance is crucial for managing and diagnosing related disorders.