Overall body fluid concentration is regulated within a narrow range by the concerted action of the hypothalamic-pituitary axis to influence water intake through thirst and water excretion via the effect of vasopressin, or antidiuretic hormone, on renal collecting duct water permeability. Sodium is the principal extracellular cation; abnormalities in overall effective body fluid concentration, or tonicity, manifest as disturbances in serum sodium concentration. Depending on its severity and chronicity, hyponatremia can lead to significant symptoms, primarily related to central nervous system function. Failure to correct hyponatremia can lead to permanent neurologic damage, as can over rapid correction. It is thus essential to stay within specific limits for correction, particularly for chronic hyponatremia. Hypernatremia also leads to central nervous system dysfunction, although goals for its correction rate are less well established. This Core Curriculum article discusses the normal regulation of tonicity and serum sodium concentration and the diagnosis and management of hypo-and hypernatremia.

BackgroundIn graduate medical education (GME), there are many barriers to achieving a personalized learning process with standardized learning outcomes. One way to support this is through mobile-friendly digital blackboard videos. We sought to measure the effect of a mobile-friendly video curriculum on resident satisfaction, knowledge, and clinical skills during a nephrology rotation.MethodsThis was a prospective, controlled, nonrandomized trial. The control group consisted of internal medicine residents who completed our inpatient nephrology consult rotation as usual. The classroom group had the same clinical experience, but also had access to a library (Nephrology Immersion Classroom) of mobile-friendly, nephrology-themed, digital blackboard videos. In a postrotation assessment, we measured resident satisfaction, clinical knowledge using 15 multiple-choice questions, and nephrology-specific clinical skills.ResultsOf the residents in the classroom group, 77% enrolled in the online classroom, and the majority reported using the classroom occasionally or frequently. A majority found it very easy to use (86%) and strongly recommended having similar videos for other rotations (77%). We observed improved report of rotation-specific clinical skills, but no difference in short-term knowledge between the two study groups.ConclusionsA mobile-friendly, digital video curriculum for internal medicine residents on an inpatient consult rotation was well utilized, highly rated, and associated with improved nephrology-specific clinical skills. Continued evaluation and incremental improvement of such resources could enhance implementation of GME core curricula.