Prognosis of patients with severe hyponatraemia is related not only to hyponatraemia but also to comorbidities and to medical management: results of an observational retrospective study

Abstract

BackgroundThe true cause of death in severe hyponatraemic patients remains controversial. The present study aimed to analyse the relationship between comorbidity, medical management and prognosis in severe hyponatraemic patients.MethodsMedical records of all patients hospitalised in our institution in 2012 with a plasma sodium ≤120 mmol/l were retrospectively analysed.ResultsOne hundred forty-seven of 64 723 adult patients (0.2 %) were identified with severe hyponatraemia. In-hospital mortality rate was 24.5 and 50.3 % after a median follow-up of 431 days. Patients with plasma sodium <110 mmol/l had less comorbidity (Charlson Comorbidity Index 2.2 ± 1.9 vs. 4.0 ± 3.1 (plasma sodium 110–115 mmol/l) and 4.2 ± 3.1 (plasma sodium 116–120 mmol/l); P = .02)) and a small trend for less mortality, respectively 40.0, 51.2 and 52.3 % (P = .64). At discharge, nonsurvivors and survivors had similar plasma sodium with 58.3 % of nonsurvivors being normonatraemic. Urine analysis was performed in 74.2 % of cases and associated with lower in-hospital mortality (20.2 % vs. 36.8 %, P = .05). In multivariate Cox analysis, mortality was significantly associated with plasma sodium normalisation (HR 0.35, P < 0.001), urine analysis (HR 0.48, P = .01), Charlson Comorbidity Index (HR 1.23, P < .001) and serum albumin (HR 0.88, P < .001).ConclusionMortality in severe hyponatraemia appears mainly due to comorbidities although the latter are potentiated by hyponatraemia itself and its management thereby exacerbating the risk of death.

Causes and Outcome of Severe Hyponatremia in Elderly Hospitalised Patients in an Indian Teaching Hospital

“…Moreover, the participants who got DAMA due to worsening clinical status could be the reason for the underestimation of the in-hospital mortality. The severity of hyponatremia was not found to be associated with mortality or poor outcome in our study which is similar to the findings in many other recent studies [25][26][27] (Table 4). In the subgroup analysis, patients with delirium had a poor outcome which was tending to achieve significance empha-sising the fact that delirium is associated with high mortality 28 .…”

Hyponatremia and activation of vasopressin secretion are both independently associated with 30‐day mortality: results of a multicenter, observational study

“…They found that both underlying comorbidities assessed by the Charlson Comorbidity Index, and low serum sodium levels on admission predicted 1‐year mortality, suggesting that the correlation of serum sodium and mortality emphasizes both serum sodium itself and the underlying disease . Similar to this, some recent studies suggest that the mortality in patients with hyponatremia appears mainly driven by comorbidities, but hyponatremia could have a detrimental effect by itself . Barsony et al .…”

Treatment of Severe Hyponatremia

“…Correction rates are affected by the underlying cause (30,31). Hyponatremia due to heart failure, cirrhosis, kidney injury, or malignancy does not spontaneously resolve and may not be treated; patients with these disorders often die in the hospital.…”

“…Lower serum sodium concentrations are associated with more rapid correction rates (30)(31)(32). Paradoxically, the lowest serum sodium levels are associated with the lowest mortality; hospitalized patients with very low serum sodium levels are more likely to have been admitted for medication-induced hyponatremia, and patients with milder hyponatremia are more likely to have been hospitalized for severe, potentially fatal illness (28,30,31).…”