* D5W is hypotonic: D5W is a solution containing 5% dextrose (a sugar) in water. While the initial tonicity is similar to blood, the dextrose is rapidly metabolized by the body. This leaves behind just water, making the solution hypotonic (lower solute concentration than blood).
* 0.9% NaCl is isotonic: Normal saline is isotonic because its solute concentration is similar to blood.
* Mixing them creates a hypertonic solution: When you mix D5W with 0.9% NaCl, you are essentially adding more solutes (sodium and chloride ions) to the solution. This increases the solute concentration, making the overall solution hypertonic (higher solute concentration than blood).
Important Note: This is a simplified explanation. The actual tonicity of the final solution depends on the specific volumes of D5W and NaCl mixed. However, the general principle remains: mixing D5W with NaCl will create a solution that is hypertonic to blood.
Why this matters: Administering hypertonic solutions can potentially cause fluid shifts from the intracellular space to the extracellular space, potentially leading to complications like dehydration and cellular shrinkage. It's important to carefully consider the tonicity of solutions when administering them intravenously.
