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. 2011 May;6(5):960-5.
doi: 10.2215/CJN.10101110. Epub 2011 Mar 24.

Mortality and serum sodium: do patients die from or with hyponatremia?

Arun Chawla  1 , Richard H Sterns, Sagar U Nigwekar, Joseph D Cappuccio
Affiliations

Mortality and serum sodium: do patients die from or with hyponatremia?

Arun Chawla et al. Clin J Am Soc Nephrol. 2011 May.

Abstract

Background and objectives: Severe hyponatremia (<120 mEq/L) in hospitalized patients has a high mortality rate. We hypothesized that underlying diseases causing hyponatremia attribute to mortality rather than hyponatremia itself.

Design, setting, participants, & measurements: The relationship between mortality and serum sodium (sNa) was examined in 45,693 patients admitted to a single community teaching hospital between January 1996 and December 2007. We conducted a comprehensive retrospective review of the medical records of 53 patients who died after developing sNa <120 mEq/L before or after admission and of 32 patients who survived after developing sNa <110 mEq/L.

Results: Mortality rates tended to increase as the sNa fell from 134 to 120 mEq/L, rising above 10% for patients with sNa of 120 to 124 mEq/L. However, below sNa of 120 mEq/L, the trend reversed, such that the mortality rate progressively decreased as sNa fell. More than two thirds of patients who died after sNa <120 mEq/L had at least two additional acute severe progressive illnesses, most commonly sepsis and multiorgan failure. Three deaths (5.6%) in 12 years could plausibly be related to adverse consequences of hyponatremia, and one (1.8% of the fatal cases and 0.15% of all patients with sNa <120 mEq/L) was from cerebral edema. Most patients who survived with sNa <110 mEq/L had medication-induced hyponatremia. Severe underlying illnesses were uncommon in this group.

Conclusions: The nature of underlying illness rather than the severity of hyponatremia best explains mortality associated with hyponatremia. Neurologic complications from hyponatremia are uncommon among patients who die with hyponatremia.

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Figures

Figure 1.
Figure 1.
Relationship between sNa uncorrected for the effect of hyperglycemia and mortality in patients admitted between 1996 and 2007.
Figure 2.
Figure 2.
Relationship between sNa corrected for the effect of hyperglycemia and mortality in patients admitted between 2004 and 2007: 130 to 134 (n = 11,742), 125 to 129 (n = 2400), 120 to 124 (n = 474), 115 to 119 (n = 139), 110 to 114 (n = 39), and <110 mEq/L (n = 5).
See this image and copyright information in PMC

Comment in

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