Lecture Notes: Isotonic, Hypotonic, and Hypertonic Solutions

Objective

• Understand the effects of isotonic, hypotonic, and hypertonic solutions on cells.
• Learn about the types of fluids ordered for patients in these conditions.
• Key concepts for exams and NCLEX.

Introduction

• Visit registernursern.com for a quiz on these solutions and additional scenarios.
• Understanding osmosis is crucial for these topics.

Cell and Osmosis Basics

• Intracellular: Inside the cell, contains organelles and electrolytes.
• Extracellular: Fluid surrounding the cell, also contains electrolytes.
• Osmosis: Movement of water from lower concentration to higher concentration through a semi-permeable membrane.
• Analogy: Sodium is the popular kid; water follows sodium.

Types of Solutions

Isotonic Solutions

• Definition: Equal concentration inside and outside the cell.
• Types of Fluids:
  • 0.9% Saline
  • Dextrose 5% in Water (D5W) - isotonic before administration, hypotonic after.
  • 5% Dextrose and 0.225% Saline
  • Lactated Ringers (LR)
• Purpose: Increase extracellular fluid volume (e.g., blood loss, dehydration, surgery).
• Effect on Cells: No shrinkage or swelling; restores volume.

Hypotonic Solutions

• Definition: Lower concentration of solutes than inside the cell.
• Types of Fluids:
  • 0.45% Saline (half normal saline)
  • 0.22% Saline (one-fourth saline)
  • 0.33% Saline (one-third saline)
  • D5W (after metabolism)
• Purpose: Rehydrate shrunken cells (e.g., diabetic ketoacidosis, hyperosmolar hyperglycemia).
• Effect on Cells: Swells up, risk of cell lysis and hypovolemia.
• Contraindications:
  • Increased intracranial pressure
  • Patients with burns or trauma

Hypertonic Solutions

• Definition: Higher concentration of solutes outside the cell.
• Types of Fluids:
  • 3% Saline
  • 5% Saline
  • 10% Dextrose in Water
  • 5% Dextrose in 0.9% Saline
  • 5% Dextrose in half normal saline
  • 5% Dextrose in LR
• Purpose: Pull fluid from cells (e.g., cerebral edema, hyponatremia).
• Effect on Cells: Cells shrink.
• Monitoring: Intensive Care Unit, risk of fluid overload and pulmonary edema, given via central line.