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Fluctuations in serum sodium level are associated with an increased risk of death in surgical ICU patients

Introduction

Dysnatremia may have an impact on outcomes in critically ill patients, but this has not been widely investigated in surgical ICU patients. We investigated the epidemiology of dysnatremia in a large cohort of surgical ICU patients and evaluated the possible influence of the time of acquisition of dysnatremia and fluctuations in serum sodium concentrations on hospital mortality in these patients.

Methods

All patients admitted to the ICU between January 2004 and January 2009 were included retrospectively in this study. Hyponatremia was defined as a serum sodium concentration (sNa) <135 mmol/l and hypernatremia as a sNa >145 mmol/l. Hyponatremia was defined as a sNa less than 135 mmol/l and hypernatremia as a sNa greater than 145 mmol/l. Patients were classified according to the onset of dysnatremia into those who had abnormal sodium concentrations in the initial blood sample, analyzed within 2 hours of admission to the ICU, or those acquiring dysnatremia thereafter. We performed a logistic regression multivariate analysis with hospital outcome as the dependent factor to investigate the possible influence of dysnatremia on hospital outcome.

Results

Of the 10,923 surgical ICU patients included in the study, 1,215 (11.2%) had hyponatremia and 277 (2.5%) hypernatremia at admission to the ICU. Among patients with normonatremia at admission to the ICU (n = 9,431), the incidence of ICU-acquired dysnatremia was 31.3%. Dysnatremia present at ICU admission (OR = 2.53; 95% CI: 2.06 to 3.12, P < 0.001) and ICU-acquired dysnatremia (OR = 2.06; 95% CI: 1.71 to 2.48, P < 0.001) were independently associated with an increased risk of in-hospital death. Dysnatremia at ICU admission (OR = 1.23; 95% CI: 1.01 to 1.50) was associated with a higher risk of in-hospital death, compared to ICU-acquired dysnatremia. Fluctuation in serum sodium concentration was also independently associated with an increased risk of in-hospital mortality; both in patients who remained normonatremic (>6 mmol/l/ICU stay) and those with dysnatremia (>12 mmol/l/24 hours or >12 mmol/l/ICU stay).

Conclusion

Dysnatremia was common in surgical ICU patients and was independently associated with an increased risk of in-hospital death in these patients. Dysnatremia at ICU admission was associated with a higher risk of death compared to ICU-acquired dysnatremia. Fluctuations in serum sodium concentrations were independently associated with an increased risk of in-hospital death, even in patients who remained normonatremic during the ICU stay.

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Correspondence to Y Sakr.

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Sakr, Y., Rother, S., Ferreira, A. et al. Fluctuations in serum sodium level are associated with an increased risk of death in surgical ICU patients. Crit Care 16, P145 (2012). https://doi.org/10.1186/cc10752

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Keywords

  • Large Cohort
  • Hospital Mortality
  • Logistic Regression Multivariate Analysis
  • Serum Sodium
  • Sodium Concentration