| Background Serum sodium is one of the most abundant electrolytes in plasma,which plays an important role in maintaining the osmotic balance of extracellular fluid and determines the water distribution between extracellular fluid and intracellular fluid.Abnormal sodium levels can be caused by various disease states and many different situations.A considerable number of patients experience sodium metabolism disorders during the ICU period,with hyponatremia being the most common electrolyte disorder among hospitalized patients and also common among intensive care unit(ICU)patients.Previous studies have shown that patients with hyponatremia have a higher mortality rate.Mild hyponatremia(serum sodium>125mmol/L),which has long been considered insignificant,is associated with adverse consequences.Persistent mild hyponatremia may alter the function of multiple organ systems and have adverse effects on their function and the survival of organisms.Numerous studies have shown that even if serum sodium levels are slightly below the normal range,it can lead to an increase in mortality.A study showed that among 36660 patients in the Dutch ICU from January 2011 to April 2017,the incidence of mild hyponatremia(serum sodium125-135mol/L)at admission to the ICU was 22%,the hospital mortality rate was as high as 23.28%(1878/8068),the incidence of severe hyponatremia(serum sodium<125 mmol/L)was 1.4%,and the hospital mortality rate was as high as 29.98%(149/497).A meta-analysis of 81 such studies,including 147948 participants,found that mild hyponatremia significantly increased overall mortality(HR 2.60,95%CI 2.31-2.93).The higher mortality rate of patients with mild hyponatremia reflects the severity of underlying diseases.Objective Mild hyponatremia is common in intensive care units(ICUs)with a high mortality rate.The association between changes in blood sodium concentration and mortality remains unclear.This study aimed to investigate the correlation between abnormal serum sodium and hospital mortality,as well as between changes in serum sodium and hospital mortality in patients with hyponatremia in ICU.Research methods A retrospective analysis was conducted on patients who were admitted to the Beth Israel Deacon Medical Center for the first time and had serum sodium monitored within 24 hours of admission to the ICU,extracted from the Medical Information Mart for Intensive Care(MIMIC)-IV.The main outcome of the study was hospitalization mortality.This study constructed a logistic regression model with stepwise adjustment for confounding factors to evaluate the association between serum sodium and hospitalization mortality.This study used multivariate Cox regression analysis to calculate the adjusted risk ratio(HR)for the 95% confidence interval(95% CI).The secondary outcome was the incidence of severe consciousness disorders.This study used multivariate logistic regression analysis to calculate the adjusted odds ratio(OR)for 95% CI.Results This study included an analysis of 47783 adult critically ill patients(aged ≥ 18years)hospitalized in the ICU of Beth Israel Deacon Medical Center from 2008 to2019(inclusive).Patients who were only admitted to the ICU for the first time were included,and serum sodium measurements(baseline blood sodium)were taken at least once within 24 hours of admission.Compared with the baseline normal blood sodium group,patients with abnormal serum sodium had longer hospital stay and ICU stay,higher hospital mortality rate,and statistically significant differences between groups(p<0.001).In further research,6575 mild hyponatremia patients in the ICU had an overall hospitalization mortality rate of 12.2%(804/6575).After adjusting for potential confounding factors,this study found that patients in the 0.5-0.75mmol/L group with an increase in serum sodium per hour had the lowest hospitalization mortality rate,and their HR was consistently significant.Multivariate COX regression analysis showed that compared with the daily increase in serum sodium [6-8] mmol/L group,daily increase in serum sodium<6mmol/L(adjusted HR=1.64,95% CI1.07-2.52,P=0.024)and ≥ 8mmol/L groups were associated with lower hospitalization mortality(adjusted HR=2.05,95% CI 1.17-3.59,P=0.012).Daily increase in serum sodium ≥ 8mmol/L was associated with a higher incidence of severe consciousness disorders(adjusted OR=1.67,95% CI 1.08-2.6,p=0.022).Conclusions The population with abnormal serum sodium in ICU patients has a higher risk of hospital death than the population with normal serum sodium.In further analysis,in patients with mild hyponatremia in the ICU,an increase of 0.5-0.75 mmol/L of serum sodium per hour and a daily increase of 6-8 mmol/L were associated with lower hospital mortality.A daily increase in serum sodium of ≥ 8 mmol/L is associated with the incidence of severe cognitive impairment. |
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