Electrolyte disturbances in neurology
Inappropriate secretion of ADH (SIADH):
Serum sodium may drop < 130 meq/L, while urine sodium may be >80 meq/L and the urine/plasma osmolality ratio >2.
Cerebral salt wasting:
Involves the secretion of atrial natriuretic peptide and brain-derived natriuretic factor. I is characterized by acute, intermittent excessive diuresis of salt and water, leading to signs of volume depletion. Serum sodium may be <130 meq/L, while urine sodium may be >80 meq/L and the urine/plasma osmolality ratio usually greater than >2 (but not SIADH), and normal or elevated serum uric acid. There is also a negative salt and water balance. It starts after the first week of CNS insult, and it last about 2 to 4 weeks. Management involves volume repletion and administration of hypertonic saline, and contrary to SIADH no volume restriction should be prescribed. The administration of 5% albumin may be beneficial.