Incidence and prognosis of dysnatremias present on ICU admission.
OBJECTIVE
Dysnatremias are common in patients admitted to the intensive care unit (ICU). Whether the presence of disorders of sodium balance on ICU admission is independently associated with excess mortality is unknown. We hypothesized that dysnatremias at the time of ICU admission are independent risk factors for increased mortality in critically ill patients.


METHODS
We conducted a retrospective study in 77 medical, surgical, and mixed ICUs in Austria, with a database of 151,486 adults admitted consecutively over a period of 10 years (1998-2007).


RESULTS
Most patients (114,170, 75.4%) had normal sodium levels (135 < or = Na < or = 145 mmol/L) on ICU admission. The frequencies of borderline (130 < or = Na < 135 mmol/L), mild (125 < or = Na < 130 mmol/L), and severe hyponatremia (Na < 125 mmol/L) were 13.8%, 2.7%, and 1.2%, respectively. The frequencies of borderline (145 < Na < or = 150 mmol/L), mild (150 < Na < or = 155 mmol/L), and severe hypernatremia (Na > 155 mmol/L) were 5.1%, 1.2%, and 0.6%, respectively. All types and grades of dysnatremia were associated with increased raw and risk-adjusted hospital mortality ratios. Multiple logistic regression analysis showed an independent mortality risk rising with increasing severity of both hyponatremia and hypernatremia. Odds ratios and 95% confidence interval (CI) for borderline, mild, and severe hyponatremia were 1.32 (1.25-1.39), 1.89 (1.71-2.09), and 1.81 (1.56-2.10), respectively. Odds ratios and 95% CI for borderline, mild, and severe hypernatremia were 1.48 (1.36-1.61), 2.32 (1.98-2.73), and 3.64 (2.88-4.61), respectively.


CONCLUSIONS
Our results suggest that both hypo- and hypernatremia present on admission to the ICU are independent risk factors for poor prognosis.
Department of Respiratory and Critical Care Medicine, Otto Wagner Spital, Vienna, Austria. georg-christian.funk@wienkav.at
Georg-Christian
GC
Funk
Gregor
G
Lindner
Wilfred
W
Druml
Barbara
B
Metnitz
Christoph
C
Schwarz
Peter
P
Bauer
Philipp G H
PG
Metnitz
D000293:Adolescent; D000328:Adult; D006801:Humans; D006955:Hypernatremia / Q000453:epidemiology* / Q000503:physiopathology; D007010:Hyponatremia / Q000453:epidemiology* / Q000503:physiopathology; D015994:Incidence; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D010343:Patient Admission / Q000706:statistics & numerical data*; D011379:Prognosis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D055815:Young Adult