Neurologic Consequences of Electrolyte Disorders

Abstract

Characteristically, several fluid and electrolyte disorders have dysfunction of the central nervous system (CNS) as a major complication. The brain, within a closed space, cannot respond quickly or effectively to prevent the acute stresses of osmotic swelling or contraction of extracellular and/or intracellular spaces. Disorders of many other ions and neutral molecules can lead to pathology, including cognitive abnormalities, encephalopathy, falls, and seizures. This chapter looks at osmolar change and brain volume regulation and the importance of sodium (Na), potassium, phosphate, and magnesium. The section on sodium looks at its importance to serum osmolality and discusses hyponatremia and hypernatremia, syndrome of inappropriate antidiuretic hormone (SIADH) and cerebral salt wasting, dialysis disequilibrium syndrome, and the CNS effects of elevated ammonia and altered glucose levels. The section on potassium discusses the ratio between the intracellular and extracellular potassium concentrations and looks at hypokalemia and hyperkalemia. Phosphate plays a vital role in energy metabolism, and this section explores hypercalcemia and hypocalcemia. Magnesium’s role in cell proliferation and energy metabolism is discussed, with subsections on hypomagnesemia and hypermagnesemia. Tables list symptoms of electrolyte disorders, ways to distinguish between SIADH and cerebral salt wasting, risk factors for osmotic demyelination, and expansion and contraction syndromes. Figures include a graph showing serum Na against urine osmolality in a patient with symptomatic hyponatremia, and a chart of a woman with hyperammonemia and severe metabolic acidosis. This chapter contains 2 highly rendered figures, 4 tables, 65 references, 5 MCQs.