[Hyponatremia upon admission in patients over 65 years of age. Relation with medium length of stay and hospital mortality].

OBJECTIVE

To determine the relation between natremia levels equal to or lower than 130 mEq/l upon admission, and average length of stay and hospital mortality in patients with more than 65 years of age.

DESIGN

Prospective case-control study lasting one year.

LOCATION

Complejo Hospitalario San Millán-San Pedro (second-level hospital) in Logroño (La Rioja).

CASES

patients with more than 65 years of age and natremia levels equal to or lower than 130 mEq/l upon admission.

CONTROL

normonatremic patients matched by age and sex.

VARIABLES

average length of stay and hospital mortality. Comparative tests: Z-test comparing two mean values and Yate's chi-square continuity correction.

RESULTS

With a 95% confidence, we have verified that the average length of stay of hyponatremic patients is between 1.44 and 9.2 days longer than in the case of normonatremic patients and the mortality rate is between 2.1 and 28.1% greater.

CONCLUSION

Patients with hyponatremia upon admission have a longer average length of stay and a greater mortality. Plasmatic sodium levels equal to or lower than 130 mEq/l upon admission are associated to a poor prognosis in the latter evolution of the patient.