Neurologic manifestations of fluid and electrolyte disturbances.

The schema in Table 1 illustrates the inter-relationship between the major fluid and electrolyte disturbances with their primary site of involvement, that is, the CNS or peripheral nervous system (PNS), their primary effect (nervous system depression or irritability), and the major symptom complex associated with these sites and mechanisms (obtundation, seizures, muscle weakness, and tetany). As can be seen, a pattern emerges. Disorders of sodium and osmolality, whether hypernatremia (hyperNa), hyponatremia (hypoNa), hyperosmolality (hyperOsm), or hypo-osmolality (hypoOsm), all produce CNS depression with encephalopathy as the major clinical manifestation. Disorders of potassium, whether hyperkalemia (hyperK) or hypokalemia (hypoK), produce PNS depression with muscle weakness as the major clinical manifestation. On the other hand, disorders of magnesium and calcemia produce both CNS and PNS manifestations. Hypercalcemia (hyperCa) and hypermagnesemia (hyperMg) produce CNS and PNS depression with encephalopathy and muscle weakness, respectively, being the major clinical manifestations. Hypocalcemia (hypoCa) and hypomagnesemia (hypoMg) produce CNS and PNS irritability with seizures and tetany, respectively, being the major clinical manifestations.