A mistake has been made on your floor of the hospital. Somehow, instead of infus

Question

A mistake has been made on your floor of the hospital. Somehow, instead of infusing 1 liter of isotonic saline solution into a patient, 1 liter of pure water was infused instead (yikes!). Isotonic solution should have been infused in this particular patient (because the patient lost isotonic fluid due to loss of plasma with a hemorrhage) and pure water will change the osmolarity of the ECF of this patient.

Assuming that before the infusion described above the patient’s ECF and ICF osmolarity were normal, this patient who received the pure water infusion will have A. hyponatremia B. hypernatremia

Assuming that before the infusion described above the patient’s ECF and ICF osmolarity were normal, this patient’s cells will be more _____________ than normal after the infusion of pure water. A. swollen B. shrunken

Explanation / Answer

1. The concentration of sodium in the plasma is the ratio of total sodium content and total water content in the extracellular fluid (ECF). Before infusion of water, the patient had normal ECF and ICF osmolarity (Intracellular fluid content). Osmolarity is the number of osmoles of solute per liter of solution. Intracellular fluid is the fluid present within cells while ECF is the fluid present outside the cells.

Hence, when pure water is infused, the total water content is increased in plasma, but the total sodium content remains unaltered. Hence, the concentration of sodium in plasma will decrease. Hyponatremia is the condition where there is decreased concentration of sodium in the plasma. Hypernatremia, on the other hand, is the increased plasma sodium concentration. Hence, the infusion of pure water in the patient will cause hyponatremia.

Option A (hyponatremia)

2. The ECF water content will increase when the patient is infused with pure water. Hence, ECF osmolarity will decrease. Water will cause the environment to become a hypotonic solution. Hence, due to osmosis, water will enter into the cell. The cell will become swollen. RBCs will hemolyse if pure water is added to plasma.

Option A (Swollen)

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