A 74-year-old nursing home resident is brought to the hospital in July because of lethargy and decreased oral intake during a heat wave. Physical examination shows dry mucous membranes and poor skin turgor. Laboratory studies show sodium 158 mEq/L and serum osmolality 315 mOsm/kg. Which of the following is the most likely mechanism of his neurologic symptoms?

1. A)Increased neuromuscular excitability from low calcium
2. B)Cellular swelling from hypotonic extracellular fluid
3. C)Neuronal dehydration from hypertonic extracellular fluidGABARITO
4. D)Oligodendrocyte injury from rapid sodium correction
5. E)Cardiac membrane instability from potassium excess