In reply to 'understanding hypernatremia' and 'thiazides for hypervolemic hypernatremia: A valid therapeutic strategy?'

摘要

In reply to Dr Kahn, hypervolemic hypernatremia requires disproportionate elevations of total-body sodium content relative to total-body water. Because sodium is largely restricted to the extracellular compartment, water achieves osmotic equilibrium by moving from intracellular to extracellular space. The net result is that the extracellular space expands, total-body water is elevated, and intracellular fluid volume is decreased. These changes are most likely to occur in skeletal muscle, which has limited acute cell volume regulatory mechanisms compared with brain cells. Dr Kahn raises an important observation that in sustained hypervolemic hypernatremia, cell volume regulatory mechanisms may lead to expansion of both intracellular and extracellular fluid volumes. To our knowledge, this hypothesis has not been tested directly.