Hyponatraemia: common causes were heart failure and iatrogenic.

Clinical bottom line (level 4)

  1. Mortality was higher in patients with acute onset hyponatraemia or symptomatic hyponatraemia.
  2. The commonest causes of hyponatraemia were congestive heart failure, iatrogenic causes (fluid overload or diuretics) and SIADH.
Arieff et al: Medicine 1976; 55 (2): 121-129
Expires July 2005

The study

Case series with ?objective ?blinded outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: university hospital, USA

66 patients (aged ?, ?% male) hyponatraemia (Na <128 mmol/l) referred for renal consultation



Outcomes studied:
  • mortality with acute hyponatraemia <12 hours
  • mortality with chronic symptomatic hyponatraemia
  • mortality with asymptomatic hyponatraemia
  • cause: congestive heart failure
  • cause: SIADH
  • cause: post-surgical (overtransfusion with 5% dextrose)
  • fluid overload
  • cause: dieuretic use usually due to diuretic use
  • cause: chronic renal failure
  • cause: acute renal failure

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    mortality with acute hyponatraemia ? 7/14 50%
    (24% to 76%)
    mortality with chronic symptomatic hyponatraemia ? 3/25 12%
    (0.0% to 25%)
    mortality with asymptomatic hyponatraemia ? 0/27 0.0%
    (0.0% to 11%)
    cause: congestive heart failure ? 20/66 30%
    (19% to 41%)
    cause: SIADH ? 17/66 26%
    (15% to 36%)
    cause: post-surgical (overtransfusion with 5% dextrose) ? 12/66 18%
    (8.9% to 28%)
    fluid overload ? 11/66 17%
    (7.7% to 26%)
    cause: dieuretic use ? 10/66 15%
    (6.5% to 24%)
    cause: chronic renal failure ? 8/66 12%
    (4.2% to 20%)
    cause: acute renal failure ? 8/66 12%
    (4.2% to 20%)

    Comments

    1. The spectrum of causes is not representative for the cases seen in todays ER.
    2. The mortality data are useless since they are in part due to overly rapid correction of patients with chronic hyponatremia which probably resulted in central pontine and extrapontine myelinolysis causing coma and death.

    Citation

    1. Arieff AI, Llach F, Massry SG: Neurological manifestations and morbidity of hyponatremia: correlation with brain water and electrolytes. Medicine 1976; 55 (2): 121-129
    Search Terms: hyponatrem* in Medline
    Contributor: Chris Ball and Clare Wotton, July 2000
    Reviewer: Andreas Cerny

    Clinical Question.
    Patient hyponatraemia
    Intervention or Exposure type
    Outcome mortality