Comparison of the Serum Electrolyte Levels among Patients Died and Survived in the Intensive Care Unit

Tanaffos. 2012;11(4):36-42.


Background: This study aimed to evaluate the prevalence of serum sodium and potassium disorders and assess their effects on mortality rate in hospitalized patients in the ICU and also to identify prognosis and predictors of survival.

Materials and methods: A retrospective case-control study was conducted on 457 hospitalized patients in the ICU of Rasoul-e-Akram Hospital (Tehran, Iran). There were two groups: 239 patients who died in the ICU(cases) and 218 patients who were discharged from the ICU(controls). Normal serum concentrations of sodium and potassium were considered as 135-150 and 3-5.5 mEq/L, respectively. Data were analyzed using Chi square test, Independent t-test, One Way ANOVA, Correlation and Receiver Operating Characteristic (ROC) curve.

Results: The mean serum sodium concentration in patients who died and discharged patients was 137.56(SD=8.56) and 137.17(SD=5.11) mEq/L, respectively. Whereas, hyponatremia was significantly more common in expired patients (39.7% vs. 28%, P<0.001). On the other hand, the mean serum potassium concentration in expired and discharged patients was 4.42(SD=0.90) and 4.16(SD=0.59)mEq/L, respectively. Hyperkalemia was significantly more common in expired patients (9.2% vs. 0.9%, P<0.001). There was a significant negative correlation between serum sodium concentration and patient's age (P=0.029, R Spearman = - 0.123). In addition, ROC analysis showed that serum potassium concentration could potentially be a predictor of death in ICU patients (P=0.003, Area Under Curve (AUC) = 0.581).

Conclusion: Hyponatremia and hyperkalemia are highly prevalent in expired ICU patients which is compatible with the findings of some other studies. Mortality of ICU patients is linked, in greater part, to organ dysfunction, but the severity of serum sodium and potassium disturbances remains a significant predictor of mortality. Thus, correcting electrolyte disturbances in ICU patients is important.

Keywords: Electrolyte disturbance; Intensive care unit (ICU); Mortality; Potassium; Sodium.