Isotonic

Definition

Isotonic solutions have the same osmotic pressure and solute concentration as plasma, producing no net fluid shift across cell membranes. Isotonic IV fluids expand intravascular volume without causing cells to swell or shrink.

Common Isotonic IV Fluids

• 0.9% Normal Saline (NS)
• Lactated Ringer's (LR)
• D5W (isotonic in the bag; becomes hypotonic after dextrose is metabolized)
• 5% albumin

Clinical Uses

Volume replacement for dehydration, hypovolemia, hemorrhage, burns, and surgical losses. NS preferred for blood transfusions (LR contains calcium that can clot blood).

Nursing Considerations

Monitor for fluid overload in patients with cardiac, renal, or hepatic disease. Track I&O, daily weights, lung sounds, edema, vital signs. Do not mix blood with LR.

NCLEX Relevance

NS for blood transfusion, never LR.