Hyponatraemia: brain damage is common and may be related to speed of replacement of sodium.

Clinical bottom line (level 4)

  1. Around half of patients with severe hyponatraemia have persistent CNS dysfunction- a half of them have pontine lesions.
  2. Patients with CNS dysfunction have a more rapid increase in sodium levels at 24 and 48 hours.
Brunner et al: Annals of Neurology 1990; 27: 61-66
Expires July 2005

The study

Prospective cohort study with unblinded, unobjective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: university hospital, UK

13 patients (aged range 37 to 83 years; mean 64, 77% female) serum sodium <115 mmol/l


100% followed for 1 month
Outcomes studied:
  • pontine lesions
  • persistent neurological deficit

    • All patients had MRI scans within one week of therapy and another two scans within one month.

    The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    pontine lesions 1 month 3/13 23.1%
    (0.2% to 46%)
    persistent neurological deficit 1 month 7/13 53.9%
    (26.8% to 81%)

    • correction rate at 24 hours (mmol/l):
      • no pontine lesion (SD) 0.74 (0.32)
      • pontine lesion (SD) 1.25 (0.4)
      • mean difference (95% CI) 0.51 (0.023 to 0.997)
    • correction rate at 24 hours (mmol/hr)
      • no deficit (SD) 0.6 (0.3)
      • deficit (SD) 1.1 (0.3)
      • mean difference (95% CI) 0.5 (0.13 to 0.87)
    • correction rate at 48 hours (mmol/hr):
      • no deficit (SD) 0.4 (0.1)
      • deficit (SD) 0.7 (0.2)
      • mean difference (95% CI) 0.3 (0.10 to 0.50)
    • No other clear differences in terms of age, sex, initial sodium levels or time to achieve maximum sodium levels were noted between the two groups.
    • Causes of hyponatraemia: Addison's disease and hypotonic fluid administration (1), SIADH (6), diuretic therapy (4), bladder irrigation post-prostatectomy (2).

    Citation

    1. Brunner JE, Redmond JM, Hagger AM, et al: Central pontine myelinolysis and pontine lesions after rapid correction of hyponatremia: a prospective magnetic resonance imaging study. Annals of Neurology 1990; 27: 61-66
    Search Terms: hyponatrem* in Medline
    Contributor: Chris Ball and Musab Hayatli, July 2000
    Reviewer:

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