Foundations of Nursing: Fluid, Electrolyte, and Acid-Based Balance

Key Concepts

• Fluid is crucial for cellular function and surrounds all body cells.
• Electrolytes: Sodium, potassium, calcium, magnesium, chloride, bicarbonate.
• Acid-base balance is essential for maintaining health and function of body systems.

Characteristics of Body Fluids

• Amount/Volume
• Concentration (Osmolality)
• Composition (Electrolyte Concentration)
• Degree of Acidity (pH)

Fluid Compartments

• Intracellular Fluid (ICF): Inside cells (2/3 of body water).
• Extracellular Fluid (ECF): Outside cells (1/3 of body water).
  • Intravascular Fluid: Plasma.
  • Interstitial Fluid: Between cells/outside blood vessels.
  • Transcellular Fluids: Cerebrospinal, pleural, peritoneal, synovial fluids.

Movement of Water and Electrolytes

• Active Transport: Requires ATP to move substances against gradient (e.g., sodium-potassium pump).
• Diffusion: Passive movement down a concentration gradient.
• Osmosis: Movement of water from lower to higher particle concentration.
• Filtration: Movement across capillaries influenced by hydrostatic and osmotic pressures.

Fluid Intake and Output

• Intake: Oral, IV, rectal, metabolism (average 2300 mL/day).
• Output: Skin, lungs, GI tract, kidneys.
• Regulatory Hormones:
  • Antidiuretic Hormone (ADH): Regulates urine output.
  • Renin-Angiotensin-Aldosterone System (RAAS): Regulates ECF volume and blood pressure.
  • Atrial Natriuretic Peptide (ANP): Increases sodium and water excretion.

Fluid Imbalances

• Volume Imbalances: Disturbance in fluid amount in the ECF.
  • ECV Deficit (Hypovolemia): Insufficient isotonic fluid.
  • ECV Excess: Overhydration.
• Osmolality Imbalances: Disturbance in fluid concentration.
  • Hypernatremia: High sodium concentration.
  • Hyponatremia: Low sodium concentration.
• Clinical Dehydration: Combination of ECV deficit and hypernatremia.

Electrolyte Imbalances

• Potassium:
  • Hypokalemia: Low potassium, causes muscle weakness, arrhythmias.
  • Hyperkalemia: High potassium, causes muscle weakness, cardiac issues.
• Calcium:
  • Hypocalcemia: Low calcium, increases neuromuscular excitability.
  • Hypercalcemia: High calcium, decreases neuromuscular excitability.
• Magnesium:
  • Hypomagnesemia: Low magnesium, increases neuromuscular excitability.
  • Hypermagnesemia: High magnesium, decreases neuromuscular excitability.

Case Study: Mrs. Mendoza

• Background: 77 years old, fell after vomiting and diarrhea.
• Care Plan:
  • Assessment: Nausea, GI function, vitals, dehydration indicators, lab values.
  • Findings: ECV deficit, low potassium and sodium, dehydration.
  • Interventions: Fluid replacement, antidiarrheal medications, monitoring I&O, dietary potassium.

Summary

• Fluid, electrolyte, and acid-base balances are crucial for physiological function.
• Imbalances can result from various causes and require careful monitoring and intervention.
• Understanding these concepts is critical for effective nursing care.