Neurologic sequelae after treatment of severe hyponatremia: a multicenter perspective

Severe, symptomatic hyponatremia is often treated urgently to increase the serum sodium to 120 to 130 mmol/L. Recently, this approach has been challenged by evidence linking "rapid correction" (> 12 mmol/L per day) to demyelinating brain lesions. However, the relative risks of persistent, severe hyponatremia and iatrogenic injury have not been well quantified. Data were sought on patients with serum sodium levels < or = 105 mmol/L from the membership of the American Society of Nephrology. Respondents were given a report form asking specific questions regarding the cause of hyponatremia, presenting symptoms, rate of correction, and neurologic sequelae. Data on 56 patients were analyzed. Fourteen developed posttherapeutic complications (10 permanent, 4 transient) after correction to a serum sodium > 120 mmol/L. Eleven of these 14 patients (including 3 with documented central pontine myelinolysis) had a biphasic course in which neurologic findings initially improved and then worsened on the second to sixth day. Posttherapeutic complications were not explained by age, sex, alcoholism, presenting symptoms, or hypoxic episodes. Increased chronicity of hyponatremia and a high rate of correction in the first 48 h of treatment were significantly associated with complications. No neurologic complications were observed among patients corrected by < 12 mmol/L per 24 h or by < 18 mmol/L per 48 h or in whom the average rate of correction to a serum sodium of 120 mmol/L was < or = 0.55 mmol/L per hour. It was concluded that patients with severe chronic hyponatremia are most likely to avoid neurologic complications when their electrolyte disturbance is corrected slowly.