OBJECTIVETo investigate etiologic factors,mechanisms and treatment of hyponatremia in patients with acute spinal cord injury.

METHODSFrom January 2005 to July 2010, 57 patients with hyponatremia after acute spinal cord injuries from severe trauma were treated. They included 46 males and 11 females who ranged in age from 26 to 69 years (mean 39.5 years). Of the 57 cases, 55 cases were complicated by cervical dislocation or fracture, and the remaining two cases were without dislocation or fracture. Among them, 28 patients had complete spinal cord injury, 29 had incomplete spinal cord injury. Nerve function was assessed according to the ASIA criteria, revealing type A in 28 cases, type B in 25 cases, and type C in 4 cases. Heart rate, blood pressure, 24-hour urine volume and serum sodium were measured daily, and fluid and sodium replacement was administered when the diagnosis of hyponatremia was confirmed. Urine sodium, serum osmotic pressure and urine osmotic pressure were measured every 3 days. The potential cause of the hyponatremia was supposed to be cerebral salt wasting syndrome (CSWS) or inappropriate antidiuretic hormone secretion (SIADH) according to the results and therapeutic reaction. Intravenous fluid infusion and salt replacement were required in patients with CSWS, while fluid restriction and intravenous salt replacement were administered for patients with SIADH. Parameters before and after treatment were analyzed with t-test.

RESULTSThere were 42 patients with SCWS,and 15 patients with SIADH. Heart rate, serum sodium and serum osmotic pressure were higher 3 weeks after admission in all patients (all P < 0.01), while blood pressure and urine osmotic pressure were higher and urine sodium was lower (all P < 0.05). There was no significant difference in 24-h urine volume (P > 0.05). Heart rate, serum osmotic pressure, urine osmotic pressure showed further improvement by the time of discharge, while 24-h urine volume decreased, urine sodium further decreased (all P < 0.05). There was no significant change in blood pressure (P > 0.05).

CONCLUSIONCSWS and SIADH are two potential causes of hyponatremia in patients with acute spinal cord injury. Distinguishing between these two disorders is of crucial importance because treatment of each condition is quite different, one needing vigorous salt replacement while the other needing fluid restriction.