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Table 2 Epidemiology of hyponatremia in the ICU and impact on outcome

From: Hyponatremia in the intensive care unit: How to avoid a Zugzwang situation?

First author, year of publication

Study methodology

Definition of hyponatremia

Number/total population (%)c

Patient characteristics associated with hyponatremia

Outcomes significantly associated with hyponatremia

Univariate analysis

Multivariate analysis

Studied variable

Outcomee

Vandergheinst, 2013

Prospective, 1 day multicentric 1265 ICUs

<135 mmol/L

1713/13,796 (12.9 %)

SAPS II

SOFA

ICU LOS (129 < PNa < 135)

Cirrhosis (PNa < 130)

Infection (125 < PNa < 135)

Medical (PNa < 125)

–

Hyponatremia, according to severity and type

Increased hospital mortality (whole population)f

1. Severity of hyponatremiaa

2. Type of hyponatremia

 On admission

 ICU acquiredb

3. Whole population

Sakr, 2013

Retrospective

Monocentric

1 ICU

<135 mmol/L

1215/10,923d (11.2 %)

SAPSII

ICU LOS

Diabetes

Cancer

Hematological cancer

AKI

–

Hyponatremia on admission

Increased hospital mortality

 On admission

1483/10,923d (13.6 %)

 ICU acquiredb

Darmon, 2013

Retrospective 13 ICUs

<135 mmol/L

Severity of hyponatremiaa on admission

3047/11,125 (9.7 %)

  

Hyponatremia according to severity

Increased day-30 mortality (for moderate and severe hyponatremia)h

Study, year of publication

Study methodology

Definition of hyponatremia

Number/total population (%)c

Patient characteristics associated with hyponatremia

Hyponatremia as a risk factor for ICU

Univariate analysis

Multivariate analysis

Studied variable

Outcomee

Funk, 2010

Retrospective multicentric 77 ICUs

= or <135 mmol/L on admission

26,782/151,486 (17.7 %)

–

–

Hyponatremia

Increased hospital mortality

Stelfox, 2008

Retrospective multicentric 3 ICUs

<133 mmol/L

ICU acquiredb

917/8142 (11 %)

–

Age

Setting

Hyponatremia

Increased ICU mortality

 Neurosurgical

 Surgical

 Trauma patients

APACHE II

GCS score

Glucose level

K+ >5 mmol/L

T° > 37.3 °C and T° °C < 35 °C

Bennani, 2003

Retrospective monocentric 1 ICU

<130 mmol/L

Severity of hyponatremiag on admission

300/2188 (13.7 %)

  

Hyponatremia according to severity

Increased hospital mortality (PNa < 125 mmol/L)

deVita, 1990

Retrospective monocentric 1 ICU

<135 mmol/L on admission

24/98 (24.5 %)

_

_

–

–

  1. ICU intensive care unit
  2. aAs defined by mild hyponatremia: PNa comprised between 130 and 134 mmol/L, moderate hyponatremia: PNa comprised between 125 and 129 mmol/L, severe hyponatremia: PNa <125 mmol/L
  3. bAcquired during the ICU stay
  4. cThe variables are number of patients with hyponatremia, total number of patients admitted during the study period, percentage of patients with hyponatremia (%)
  5. dNumber of patients with hyponatremia, total number of patients admitted during the study period, percentage of patients with hyponatremia (%) upon ICU admission and acquired during the ICU stay
  6. eIn each case there is a positive correlation between the studied variable and the defined outcome
  7. fPatients with hyponatremia admitted in the ICU during the study day or prior to the study day
  8. gAs defined by mild hyponatremia: PNa comprised between 125 and 129 mmol/L, moderate hyponatremia: PNa comprised between 120 and 124 mmol/L, severe hyponatremia: PNa <120 mmol/L
  9. hAs defined by moderate hyponatremia: PNa comprised between 125 and 129 mmol/L, severe hyponatremia: PNa <125 mmol/L