Which fluid is typically used for replacement in a patient with a fluid volume deficit?

• A. Dextran.
• B. 0.45% Saline.
• C. Lactated Ringer's Solution.
• D. 5% Dextrose in 0.45% Saline.

Answer: (C)

When replacing a fluid volume deficit, you want an IV fluid that stays in the extracellular space and expands circulating volume without causing cells to swell. Lactated Ringer's Solution is a balanced isotonic crystalloid that mirrors plasma electrolyte levels (sodium, chloride, potassium, calcium) and includes lactate, which acts as a buffer. Because it’s isotonic, it quickly increases intravascular volume and then distributes to the interstitial space to restore perfusion—making it the typical choice for acute volume replacement.

Dextran is a colloid that can expand volume but carries risks such as allergic reactions and coagulation issues, so it isn’t the first-line option for routine replacement. A solution like 0.45% saline is hypotonic, which can cause water to move into cells and isn’t ideal for rapid resuscitation. The 5% dextrose in 0.45% saline provides dextrose that is metabolized to free water, potentially diluting electrolytes and not giving sustained intravascular volume for replacement.