The nurse is caring for a patient with a serum sodium level of 155 mEq/L and cellular dehydration. The nurse expects to administer which of the following solutions?

Introduction: Hypernatremia, defined as a serum sodium concentration > 145 mEq/L, creates a hypertonic extracellular environment that draws water out of the cells via osmosis. Management requires the administration of hypotonic fluids to dilute the intravascular space and facilitate the rehydration of the intracellular compartment. A. D5 0.9% Normal Saline is a hypertonic solution. Administering a hypertonic fluid to a patient who is already hypernatremic would exacerbate the osmotic gradient, drawing even more water out of the cells and potentially worsening the neurological symptoms associated with severe cellular dehydration and elevated serum osmolality. B. Lactated Ringers (LR) is an isotonic crystalloid solution. While it is excellent for volume expansion in trauma or surgery, it contains 130 mEq/L of sodium. In the context of a sodium level of 155 mEq/L, LR is not the optimal choice for correcting the free water deficit specifically needed to resolve hypernatremia. C. 0.9% Sodium Chloride, or Normal Saline, is an isotonic solution. Although its sodium concentration (154 mEq/L) is slightly lower than the patient's current level, it does not provide enough free water to effectively lower the serum sodium. It is generally used for ECF volume depletion rather than treating primary hypernatremic dehydration. D. D5W (5% Dextrose in Water) is physiologically HYPOTONIC. Once the glucose is rapidly metabolized by the body, the remaining FREE WATER disperses across all fluid compartments. This effectively lowers the serum sodium concentration and provides the necessary water to rehydrate cells that have shrunken due to the hyperosmolar state