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Understanding Water Balance in Nursing

Aug 30, 2024

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Lecture on Water Balance and Physiology

Importance of Water Balance in Nursing

  • Humans are 60% water; crucial for nurses to track water balance in patients.
  • Nurses must record fluid intake and output (e.g., urine measurement).
  • Imbalance can lead to dehydration or overhydration.

Calculating Total Body Water (TBW)

  • Formula: TBW = 60% of body weight (in kg).
  • Conversion from pounds to kilograms necessary.
    • 1 kg ≈ 2.2 lbs.
    • Example: 154 lbs = 70 kg; TBW = 0.6 * 70 = 42 liters.

Importance of Estimation and Decimal Points

  • Before using a calculator, estimate the answer to avoid errors.
  • Decimal placement is critical: can mean life or death in medical calculations.

Reference Person in Medical Norms

  • Reference: Young adult male, 70 kg (154 lbs).
  • Historical data collected from army recruits and medical students.
  • Norms vary by age, gender, and size.

Intracellular vs. Extracellular Fluid

  • TBW is divided: 2/3 intracellular fluid (ICF), 1/3 extracellular fluid (ECF).
  • ECF includes tissue fluid, transcellular fluids, and blood plasma.

Types of Extracellular Fluids

  • Tissue Fluid: Surrounding tissue cells.
  • Blood Plasma: Within blood vessels, around blood cells.
  • Transcellular Fluids: Located in specific anatomical areas (e.g., cerebrospinal fluid, synovial fluid).

Water Movement and Fluid Compartments

  • Fluid can move between compartments; affects dehydration and conditions like edema.
  • Trauma can cause fluid shifts leading to conditions like hydrocephalus or glaucoma.

Estimating Total Blood Volume

  • TBV ≈ 8% of body weight in kg.
  • Example: 70 kg person ≈ 5.6 liters of blood.
  • Blood donation: 1 pint ≈ 10% of blood volume in typical adult.

Distribution of Electrolytes

  • Intracellular Fluid (ICF): High in potassium and magnesium.
  • Extracellular Fluid (ECF): High in sodium and chloride, with bicarbonate for pH buffering.
  • Blood plasma contains proteins; tissue fluid generally does not.

Electrolyte Concentrations

  • Differences in electrolyte composition between ICF and ECF are critical for physiological functions.
  • Plasma proteins are produced by the liver; important for various bodily functions.

These notes encapsulate the key points of the lecture, focusing on water balance, fluid compartments, estimation in medical calculations, and the role of electrolytes in body fluids. This foundational understanding is crucial for various fields in healthcare, especially nursing and medicine.

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