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IV Fluids, Body Fluid Compartments, and Osmosis

May 16, 2024

IV Fluids, Body Fluid Compartments, and Osmosis

Speaker: Sarah from registerednursern.com

Introduction

  • IV fluids (intravenous fluids): Administered to the intravascular space, part of the extracellular compartment.
  • Common treatment in hospitals.
  • Used to treat dehydration, electrolyte imbalances, acid-base imbalances.
  • Nurses must be familiar with isotonic, hypotonic, and hypertonic IV fluids.

Body Fluid Compartments

Overview

  • Human body: 60-70% water.
  • Main compartments: Intracellular (inside cells) and extracellular (outside cells).

Intracellular Compartment

  • Fluid inside the cell.
  • Accounts for two-thirds of body water.

Extracellular Compartment

  • Fluid outside the cell.
  • Accounts for one-third of body water.
  • Includes:
    • Intravascular fluid: Plasma in blood vessels.
    • Interstitial fluid: Surrounds cells.
    • Transcellular fluid: In body cavities (e.g., spinal fluid, pericardial fluid).

Interconnection and Homeostasis

  • Compartments are interconnected.
  • Maintain balance by shifting water and electrolytes through processes like osmosis.

Osmosis

  • Definition: Movement of water from high water concentration (low solute) to low water concentration (high solute).
  • Passive process, requires no energy.
  • Occurs through a semi-permeable membrane.

Key Points

  • Influenced by fluid solute concentration.
  • Solutes (e.g., sodium, chloride) dissolved in liquid affect how osmosis occurs.

Osmolarity

  • Definition: Concentration of solutes per liter of solution.
  • High osmolarity: More solutes, less water.
  • Low osmolarity: Fewer solutes, more water.
  • Used to manage fluid shifts in healthcare.

Types of IV Fluids

Isotonic IV Solutions

  • Osmolarity: Equal to blood plasma.
  • Function: Equal transfer of water; remains the same in the cell.
  • Uses: Replace extracellular fluid (e.g., fluid loss, hypovolemic shock).
  • Examples: Normal saline, lactated ringers, 5% dextrose in water (D5W starts isotonic but becomes hypotonic).

Hypotonic IV Solutions

  • Osmolarity: Lower than blood plasma.
  • Function: Causes water to move into cells, may swell and rupture cells.
  • Uses: Dilute extracellular space, provide water to cells (e.g., hypernatremia).
  • Examples: Half normal saline, 0.225% saline, 0.33% saline, D5W (once in the body).

Hypertonic IV Solutions

  • Osmolarity: Higher than blood plasma.
  • Function: Draws water out of cells to extracellular compartment; cells shrink.
  • Uses: Treat severe hyponatremia, cerebral edema.
  • Examples: 3% saline, dextrose 10% in water, D5W in normal saline, D5W in half normal saline.
  • Caution: Risk of fluid overload, hypernatremia, and tissue damage.

Nursing Considerations

  • Isotonic Solutions: Normal Saline
    • Watch for fluid overload in patients with kidney or heart failure.
    • Monitor blood pressure, lung sounds, extremities for edema.
  • D5W: Monitor for hyperglycemia.
  • Lactated Ringers: Not for patients with liver disease or lactic acidosis, monitor potassium level.
  • Hypotonic Solutions: Watch for brain swelling, mental status changes, hypovolemia, and hyponatremia.
  • Hypertonic Solutions: Administer with caution, monitor serum sodium and fluid overload.

Conclusion

  • IV fluids play a crucial role in maintaining fluid and electrolyte balance.
  • Nurses should be knowledgeable about the types of IV fluids, their uses, and potential complications.

For more information, visit registerednurseRN.com.

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