Question

0.9% saline (NaCl solution), commonly referred to clinically as Normal saline, is isosmotic and isotonic to cells in the body. Serum osmolarity is normally around 290 mOsm/liter.   Now, what would happen clinically if one infused 500 ml of Normal Saline into the vascular system of a patient? In other words, how would the water and ions (Na and Cl) be distributed in the plasma, interstitial fluid and intracellular compartment? From each grouping of three choices, pick the correct statement for each group.

A. Pick one choice from a, b and c below:

a.       The infused water would be distributed evenly between the extracellular compartment and the cells.

b.      The infused water would be distributed mostly to the intracellular space as opposed to the extracellular space.

c.       The infused water would be distributed between the extracellular compartment and very little would enter the cells.

B. Pick one choice from d, e and f below:

d.      The ions would be distributed evenly between the extracellular compartment and the cells.

e.       The ions would be distributed mostly to the intracellular space as opposed to the extracellular space.

f.        The ions would be distributed between the extracellular compartment and very little would enter the intracellular space.

Answer 1

A) c.       The infused water would be distributed between the extracellular compartment and very little would enter the cells.

B) f.        The ions would be distributed between the extracellular compartment and very little would enter the intracellular space.

Because isotonic solutions have the same concentration of solutes as plasma, infused isotonic solution doesn't move into cells. Rather, it remains within the extracellular fluid compartment .water does not have any osmotic pressure to shift between compartments, and it distributes itself according to the proportional distribution of sodium, Because water goes where sodium goes, 0.9% sodium chloride increases fluid volume in extracellular spaces. It is because of this reason why 0.9% saline is administered to treat low extracellular fluid, as in fluid volume deficit from hemorrhage, severe vomiting or diarrhea.