Which solution is isotonic with blood and commonly used for initial fluid resuscitation?

• A. Dextrose 5% in water
• B. 3% saline
• C. Normal Saline
• D. Hypotonic saline

Answer: (C)

When resuscitating a patient with volume loss, you want a fluid that expands the blood vessels quickly without pulling water into or out of cells. Normal saline (0.9% NaCl) is isotonic with blood plasma, so it stays in the intravascular space and effectively increases circulating volume to support blood pressure and perfusion.

Dextrose 5% in water may seem like a good option, but after the glucose is metabolized, it leaves free water in the bloodstream, which can dilute plasma and shift fluid into cells rather than staying in the vessels—making it less reliable for rapid volume expansion.

Hypertonic solutions like 3% saline draw water out of cells and into the intravascular space, but they are not used for routine initial resuscitation due to the risk of rapid shifts and electrolyte disturbances.

Hypotonic solutions would cause water to move into cells, potentially leading to cellular edema and worsened edema in sensitive organs like the brain—also not desirable for initial resuscitation.

Therefore, the fluid most appropriate for first-line resuscitation because it remains intravascular and expands circulating volume is normal saline.