Chapter 3 Presentation - Water and Dehydration

Water Distribution by Gender

  • Difference in Water Content: The human body water content depends on muscle mass and varies between genders.

    • Males: ~60% water due to higher muscle mass and lower fat.

    • Females: ~50% water due to lower muscle mass and higher fat.

    • Common misconception: Many think females have more body water.

  • Body Composition Breakdown:

    • 168 lb Male: 59% water, 20% fat, ~17% protein, ~5% minerals.

    • 137 lb Female: 52% water, 29% fat, 14% protein, ~5% minerals.

  • Water Locations:

    • Total water content can be estimated around half or more of body weight.

    • Rough estimation for an average person:

      • Blood: 5 liters

      • Extracellular Fluid: 19 liters (includes lymphatic and interstitial fluid)

      • Intracellular Fluid: 20 liters

Importance of Water

  • Biochemical Processes: Almost all biochemical processes occur in aqueous solutions.

  • Vital for Life: Water is the most critical nutritional compound; it is essential for survival.

    • Without macronutrients and micronutrients, one can survive for weeks, but without water, death can occur within days (3-7 days).

Osmosis and Water Retention

  • Osmosis:

    • Explains how the body retains water despite being a 'sack of water'.

    • In semi-permeable membranes, water levels equalize but when biomolecules (e.g., sugar) are added, they create 'hydration shells' around them trapping water.

  • Osmotic Process:

    • Water from one side of the membrane migrates toward the side with dissolved biomolecules, leading to higher water levels on one side of the membrane.

Osmotic Ions

  • Sodium and Potassium Ions:

    • Sodium (Na+): Works extracellularly to hold water outside the cells.

    • Potassium (K+): Works intracellularly to retain water within the cells.

Biological Solution Types

  • Solution Categories:

    • Hypotonic: Less salt outside than inside; water flows into cells, causing swelling or bursting.

    • Hypertonic: More salt outside than inside; water is drawn out of cells, causing shrinkage and possible cell death.

    • Isotonic: Equal salt concentration on both sides; water balance maintained, no effect on cell volume.

    • Importance of isotonic solutions for intravenous treatments.

Dehydration

  • Detection of Dehydration:

    • Common symptoms include headaches and color of urine; darker urine indicates dehydration.

    • Weight measurement after exertion offers a clearer hydration assessment.

  • Rehydration Strategies:

    • Forward-thinking: Pre-hydrate before activities.

    • Simple water consumption for regular rehydration; sports drinks for intense activities.

    • IV saline for medical emergencies.

Risks of Dehydration

  • High-Risk Groups:

    • Seniors: Diminished thirst response.

    • Diabetics: Excess glucose leads to increased urine output and dehydration.

    • Infants: Small body size leads to rapid dehydration from conditions like diarrhea.

    • Heavy drinkers/alcoholics: Alcohol is diuretic and leads to dehydration.

    • Marathon runners: Risk of sodium loss (hyponatremia).

Fluid Misplacement: Edemas

  • Edemas: Fluid accumulation due to misplaced water in body compartments leading to swelling.

    • Common types: Leg edema, pulmonary edema, and cerebral edema.

    • Causes may not be peripheral; e.g., a weak heart could lead to pulmonary edema.

  • Dietary Management of Edemas:

    • Many cases require medical intervention rather than nutritional changes.

    • Mild edemas in older adults can indicate heart or kidney issues, often appearing as sock lines or swelling.