Isotonic fluid

NEET SS Surgery MCQ – Isotonic Fluid (Free)
Q) Isotonic fluid solution is
  • A. Half normal saline
  • B. 1/5th normal saline
  • C. Ringer lactate
  • D. Dextrose in Normal saline

Answer: C – Ringer lactate

Ringer lactate and Normal saline are isotonic fluids. They are useful in replacing GI losses. Ringer lactate has a bit of potassium as well.

Ringer Lactate (Correct Answer):
Ringer lactate is an isotonic solution, meaning its osmolarity (around 273 mOsm/L) is close to that of human blood (around 275–295 mOsm/L). This solution contains electrolytes like sodium, potassium, calcium, and chloride, helping maintain fluid and electrolyte balance. It's commonly used for fluid replacement in surgical and trauma patients.

A. Half Normal Saline (0.45% NaCl):
Half normal saline is a hypotonic solution (~154 mOsm/L), which draws water into cells and may cause swelling—unsuitable for isotonic fluid replacement.

B. 1/5th Normal Saline (0.18% NaCl):
This is also hypotonic (~77 mOsm/L), risking excessive fluid entering cells and causing edema—unsuitable as an isotonic option.

D. Dextrose in Normal Saline (D5NS):
D5NS is hypertonic due to added dextrose, increasing osmolarity above blood levels, which can lead to water exiting cells and potential dehydration.

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