Sodium and chloride disturbances in critically ill adult patients: A protocol for a sub-study of the FLUID-ICU cohort study

BACKGROUND: Disturbances in plasma sodium and chloride are common in adults admitted to the intensive care unit (ICU) and may affect patient outcomes. Fluid administration practices in the ICU have changed in recent years with a trend toward using more restrictive fluid strategies. These changes may have influenced the patterns and proportions of electrolyte disturbances in ICU patients. Therefore, we aim to provide contemporary data on the frequency of hypernatremia, hyponatremia, hyperchloremia, and hypochloremia in adult ICU patients, assess risk factors, and association with clinical outcomes in an international cohort.

METHODS: This is the protocol for a sub-study of the FLUID-ICU study ("Fluid administration and fluid accumulation in intensive care units-an international inception cohort study"). The FLUID-ICU study is a prospective international 14-day inception cohort study with a minimum sample size of 1000 patients from more than 50 ICUs. Patients are followed daily from ICU admission to discharge or death with a maximum of 28 days. A follow-up is performed at Day 90 after ICU admission. The primary outcomes of this sub-study are the proportion of patients with hypernatremia, hyponatremia, hyperchloremia, and hypochloremia. We will assess days alive without the use of life support at Day 90, and risk factors for developing disturbances in sodium and chloride including disease severity by SMS-ICU score, type of ICU, use of diuretics, and presence of fluid accumulation. Furthermore, days alive and out of hospital and mortality at Day 90 will be reported descriptively.

CONCLUSION: In this study, we will provide important new epidemiological data on the burden of sodium and chloride disturbances in adult ICU patients internationally.