12-year HK study: Higher mortality risk with dysnatraemia at ICU admission

A retrospective, 12-year study of approximately 160,000 adult patients admitted to surgical or medical intensive care units (ICUs) in Hong Kong finds dysnatraemia at admission to be associated with higher risks of ICU and in-hospital mortality, underscoring the need for adequate fluid management before ICU stay.

Dysnatraemia (serum sodium >145 mmol/L [hypernatraemia] or <135 mmol/L [hyponatraemia]) is a common electrolyte disorder in critically ill patients. Rapid overcorrection of sodium during dysnatraemia management may result in serious neurological complications. [Intensive Care Med 2010;36:304-311; Fam Physician 2015;91:299-307] “In the study, we used territory-wide electronic public hospital health records to assess the impact of dysnatraemia at admission on clinical outcomes in ICU-admitted adult patients,” the researchers wrote.

The study included 162,026 patients (median age, 64 years; male, 61.6 percent; median Acute Physiology and Chronic Health Evaluation [APACHE] IV score, 0.12) admitted to surgical (n=70,080) or medical ICUs (n=91,946) in Hong Kong between January 2010 and June 2022. Based on their serum sodium measurement within 24 hours before or after ICU admission, dysnatraemia was identified in 49,631 patients (30.6 percent), including 9,098 patients (5.6 percent) with hypernatraemia and 40,533 patients (25.0 percent) with hyponatraemia. The remaining patients were normonatraemic (135–145 mmol/L). [Sci Rep 2023;13:21236]

Dysnatraemic patients were older (median age, 64.8 years for hypernatraemic patients and 65.3 years for hyponatraemic patients vs 63.2 years for normonatraemic patients), had a higher APACHE IV score (median, 0.3 and 0.2 vs 0.1), were more likely to be admitted from the emergency department (87.2 percent and 90.1 percent vs 72.1 percent), have COVID-19 infection (0.9 percent and 1.8 percent vs 0.7 percent), or sepsis (20.8 percent and 22.8 percent vs 12.2 percent) than normonatraemic patients (p<0.001 for each).

In the study cohort, 9.6 percent of patients died in ICU, while 16.4 percent died in hospital after ICU discharge. Patients with dysnatraemia at admission had higher rates of ICU and in-hospital mortality vs those with normonatraemia (ICU mortality rate, 21.2 percent for hypernatraemic patients and 11.6 percent for hyponatraemic patients vs 7.9 percent for normonatraemic patients; in-hospital mortality rate, 33.3 percent and 20.2 percent vs 13.6 percent; p<0.001 for both). Dysnatraemia at ICU admission was also found to be associated with increased risks of ICU (adjusted odds ratio [aOR], 1.27 for hypernatraemia and 1.14 for hyponatraemia) and in-hospital mortality (aOR, 1.52 and 1.21, respectively) in multivariable regression analysis (p<0.001 for each vs normonatraemia).

Adverse neurological events (ie, requiring ≥1 brain CT/MRI between 24 hours after ICU admission and hospital discharge) occurred in 14.5 percent of patients in the study cohort. Although most dysnatraemic patients achieved gradual sodium correction over 75 hours, 21.9 percent of patients with severe hypernatraemia (>155 mmol/L; n=253/1,154) and 14.3 percent of patients with severe hyponatraemia (<125 mmol/L; n=920/6,428) experienced adverse neurological events.

Subgroup analysis revealed an association between dysnatraemia at ICU admission and risk of ICU mortality in patients without neurological disease (aOR, 1.24 for hypernatraemia and 1.15 for hyponatraemia). Patients with hypernatraemia and neurological disease at ICU admission also had an increased ICU mortality risk (aOR, 1.65) (p<0.001 for each vs normonatraemia).

“Our results highlight the importance of proper fluid and electrolyte management for patients in the emergency department, general wards, and during peri- or intra-operative periods,” the researchers noted. “Close neurological monitoring is necessary in ICU patients with abnormal sodium levels at admission, including those without neurological disease.”