ANDRE FLUID AND ELECTROLYTES

• Homeostasis

  Maintenance of balance in the body
• Factors that threaten homeostasis

  • Illnesses
  • Extreme temperature/excessive temperature
  • Vigorous activity
  • Treatments
• Illnesses that threaten homeostasis


  • Diarrhea leading to dehydration
  • Problems of insulin production and utilization leading to diabetes mellitus
• Extreme temperature/excessive temperature


  • Global warming
  • Need to keep cool and hydrated to prevent heat stroke
• Vigorous activity


  • Excessive exercise
• Treatments that threaten homeostasis


  • Use of diuretics to promote urination and fluid excretion
  • Nasogastric suction leading to metabolic alkalosis
• Edema

  • Fluid accumulation in the body
  • Bipedal edema
  • Periorbital edema
  • Generalized (anasarca) edema
• The proportion of the human body composed of fluid is approximately 60% of the average healthy adult's weight
• An individual's weight varies by less than 0.5 lb in 24 hours, regardless of the amount of fluid ingested
• Diurnal variation


  Difference in weight measured in the morning vs evening due to fluid loss through activities
• Best way to check fluid balance

  Measuring patient's weight
• Factors influencing body water distribution

  • Age
  • Sex
  • Body fat
• Age


  Infants have the highest proportion of water (70-80% of body weight), decreasing to 50% in adults over 60
• Sex


  Women generally have a lower percentage of body water than men due to lower muscle mass and greater fat tissue
• Fat tissue


  Essentially free of water, whereas lean tissue contains a significant amount of water
• Functions of body fluids

  • Medium for metabolic reactions
  • Transport of nutrients and waste
  • Lubrication
  • Insulation and shock absorption
  • Regulating body temperature
  • Maintaining blood volume
  • Transport of gases, nutrients, etc.
  • Waste elimination
• Intracellular fluid (ICF)


  Found within the cells, constitutes 2/3 of total body fluid

  
• Extracellular fluid (ECF)


  Found outside the cells, constitutes 1/3 of total body fluid
• Components of ECF


  • Intravascular fluid (plasma)
  • Interstitial fluid
  • Lymph
  • Transcellular fluid
• Intracellular fluid


  Contains solutes like oxygen, electrolytes, glucose to support cell functioning
• Cations


  Ions with positive charge (sodium, potassium, magnesium, calcium)
• Anions


  Ions with negative charge (chloride, bicarbonate, phosphate, sulfate)
• Milliequivalent


  Refers to the chemical combining power of an ion
• Milligram


  Refers to the weight of an ion
• Extracellular fluid (ECF)


  Contains sodium and chloride as the major electrolytes
• Intracellular fluid (ICF)

  Contains potassium and magnesium as the primary cations, and phosphate and sulfate as the major anions
• Body fluid compartments


  Separated by cell membranes and capillary membranes which are selectively permeable
• Solutes


  Substances dissolved in a liquid, can be crystalloids or colloids
• Solvent


  The component of a solution that can dissolve a solute (in the body, water is the solvent)
• Osmolality


  Total solute concentration within a fluid compartment, measured in milliosmoles per kilogram (mOsm/kg)
• Sodium


  The greatest determinant of serum osmolality
• Tonicity


  Osmolality of one solution relative to another, can be isotonic, hypertonic, or hypotonic
• Osmotic pressure


  Power of a solution to pull water across a semipermeable membrane, balances hydrostatic pressure
• Colloid osmotic pressure/oncotic pressure


  Osmotic pressure exerted by plasma proteins, helps maintain vascular volume
• Methods of water and solute movement

  • Diffusion
  • Osmosis
  • Filtration
  • Active transport
• Diffusion


  Movement of solutes from high to low concentration across a semipermeable membrane
• Osmosis


  Diffusion of water across a semipermeable membrane from low to high solute concentration
• Filtration


  Movement of fluid and solutes from higher to lower pressure across a membrane
• Filtration pressure


  Pressure that drives fluid and solute movement out of a compartment
• Hydrostatic pressure


  Pressure exerted by a fluid within a closed system on the surrounding structures