Clinical outcomes associated with dynamic changes in serum sodium amongst adult patients with spontaneous subarachnoid hemorrhage and other critical illnesses: an exploratory scoping review

Raman, Vignesh; Ramanan, Mahesh; Edwards, Felicity; Ferede, Zemedu Aweke; Tippett, Vivienne; Laupland, Kevin B.

doi:10.62675/2965-2774.20260019

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NARRATIVE REVIEW • Crit. Care Sci. 38 • 2026 • https://doi.org/10.62675/2965-2774.20260019 linkcopy

Clinical outcomes associated with dynamic changes in serum sodium amongst adult patients with spontaneous subarachnoid hemorrhage and other critical illnesses: an exploratory scoping review

Authorship SCIMAGO INSTITUTIONS RANKINGS

Incident dysnatremia has been reported amongst varied intensive care unit disease populations and is associated with worse clinical outcomes, but less is known about the impacts of dynamic changes in serum sodium during intensive care unit admission. The primary objective of this study was to conduct a scoping review of the published literature on patient outcomes associated with dynamic changes in serum sodium in critically ill adults, to inform future research priorities. A scoping review was conducted according to the Joanna Briggs Institute method. PubMed^®, Embase, CINAHL, Scopus, and Web of Science databases were searched for relevant articles on sodium "change", "trajectory", "fluctuation", or "variability" in adult patients managed in the intensive care unit. Seventeen articles were extracted; seven involved patients with subarachnoid hemorrhage in the intensive care unit, and ten involved mixed or other specific primary diagnoses requiring intensive care unit admission. In subarachnoid hemorrhage, higher magnitudes of serum sodium change, independent of incident dysnatremia, are associated with greater mortality and delayed cerebral ischemia. A similar association between the magnitude of serum sodium change and mortality is observed in other intensive care unit disease populations. There is limited literature on dynamic changes in serum sodium in intensive care unit populations, but current evidence suggests that greater magnitude is associated with higher mortality and morbidity across multiple intensive care unit disease populations. Current observational literature is insufficient to establish causal links between dysnatremia and worse patient outcomes.

Keywords:
Subarachnoid hemorrhage; Traumatic brain injury; Critical illness; Dysnatremia; Serum sodium; Intensive care units

Authors	Study type	Country	Study size	Primary outcome	Secondary outcomes	Key findings
Cohen et al.(⁷)	Multi-center, prospective observational	Australia/ New Zealand	356	mRS	ICU LOS, hospital LOS	Greater variability in sodium concentrations was associated with lower mRS at 6 months, longer ICU and hospital length of stay
Eagles et al.(⁸)	Multi-center, retrospective observational	United States	413	DCI	N/A	There was a trend toward significance for the average absolute daily difference in sodium levels from admission levels during the vasospasm window as an independent predictor of DCI (p = 0.052). There was no difference in the predictive capacity for DCI when sodium fluctuations from post-aSAH days 1 - 14 were compared with those from the classic vasospasm window (days 3 - 12)
Harada et al.(⁹)	Multi-center, prospective observational	Japan	133	SVS	Stress-related hormone dynamics.	Serum sodium fluctuations were associated with SVS occurrence. Serum sodium fluctuations were associated with stress-related hormonal dynamics
Bales et al.(¹⁴)	Single-center, retrospective observational	United States	198	DCI	mRS	More patients with a sodium variability of 6 - 12 and > 12mEq/L had cerebral infarction than those with variability < 6mEq/L
Chua et al.(¹⁵)	Single-center, retrospective observational	United States	271	mRS	DCI, Radiological vasospasm, Mortality	There were no significant differences in inter-individual serum sodium values over time or in the occurrence of radiographic vasospasm, neurologic deterioration, functional outcomes, or mortality outcomes using the mixed-effect regression model. However, overall mean serum sodium levels were significantly higher in patients who had neurologic deterioration, poor functional outcome (mRS 3 - 6), and mortality
Jin et al.(¹⁹)	Multi-center, retrospective observational	United States	295	Hospital Mortality	N/A	Sodium fluctuations above 8.5mmol/L were independently associated with in-hospital mortality
Labib et al.(²⁰)	Single-center, prospective observational	Netherlands	964	DCI	N/A	Hyponatremia, hypernatremia, and fluctuations of sodium levels were not predictive of DCI. Higher sodium levels, hypernatremia, and greater fluctuations of sodium levels were significantly associated with poor outcome in were significantly associated with poor outcome in both DCI and non-DCI patients

Authors	Study type	Country	Study size, Primary diagnosis	Primary outcome	Secondary outcomes	Key findings
Darmon et al.(¹⁶)	Multi-center, prospective observational	France	11,125, unselected ICU patients	30-day mortality	N/A	Amongst unselected ICU patients, dysnatremia, including mild changes in serum sodium concentration, is an independent risk factor for 30-day mortality
Grim et al.(¹⁷)	Multi-center, retrospective observational	Netherlands	36,660, unselected ICU patients	Hospital mortality	N/A	Among unselected ICU patients, an increase in serum sodium within the first 48 hours of ICU admission was associated with higher in-hospital mortality in both normonatremic and hypernatremic patients
Huang et al.(¹⁸)	Single center, retrospective observational	United States	9,314, patients in the ICU with AKI	30-day mortality	1-year mortality	In patients with AKI, the serum sodium trajectories were independently associated with 30-day and 1-year mortality.
Marshall et al.(²¹)	Single center, retrospective observational	United States	8,600, surgical ICU patients	28-day mortality	1-year mortality, ICU mortality, and hospital mortality.	A significant association was found between sodium fluctuation and 28-day mortality, even in surgical patients who remained normonatremic during their ICU stay
Sakr et al.(²²)	Single center, retrospective observational	Germany	10,923, surgical ICU patients	In-hospital mortality	N/A	A significant association was found between sodium fluctuation and in-hospital mortality, even in surgical patients who remained normonatremic during their ICU stay
Sen et al.(²³)	Single center, retrospective observational	United States	212, severe burns	In-hospital mortality	N/A	After adjusting for total body surface area, age, ventilator days, and ICU length of stay, a higher coefficient of variation in sodium measurements was associated with mortality. Further, a large variation in sodium levels in the first 10 days of admission may be associated with increased mortality
Troché et al.(²⁴)	Single-center, retrospective observational	France	215, patients in the ICU requiring RRT	Hospital mortality	ICU mortality	Among ICU patients requiring RRT, higher serum sodium was associated with increased mortality. The only significant variable associated with RRT-induced sodium change was dialysis sodium gradient
Shen et al.(²⁵)	Single-center, retrospective observational	United States	1,038, patients in the ICU with sepsis after cardiac surgery	30-day mortality	N/A	Although the fluctuation in serum sodium remained within the normal range after cardiac surgery, a higher trajectory of serum sodium substantially increased the 30-day mortality risk in this patient cohort
Li et al.(²⁷)	Single-center, retrospective observational	United States	514, patients in the ICU with sepsis and lactic acidosis	30-day mortality	N/A	Among patients with lactic acidosis complicated by sepsis, those with stable, normal fluctuations in serum sodium levels had better 30-day survival
Harrois et al.(⁴⁰)	Multi-center, retrospective observational	Australia, Europe	240, severe TBI	28-day mortality	ICU LOS	After adjusting for baseline TBI severity, diabetes insipidus, the use of osmotherapy, the occurrence of hypernatremia hyponatremia, and center, daily serum sodium variability was significantly and independently associated with 28-day mortality

Terminology	Definition(s)/Statistical technique
Trajectory	"Group-based trajectory modeling" where patients were placed into three distinct groups depending on whether serum sodium values were ascending, descending, or "stable" at various timepoints, depending on the publication (Huang et al.,(¹⁸) Li et al.,(²⁷) Shen et al.)(²⁵)
Change	Once a definition of the normal serum sodium range was established, patients were subcategorized into mild, moderate, and severe hypo- and hypernatraemia groups (Darmon et al.,(¹⁶) Grim et al.,(¹⁷) Troché et al.)(²⁴)
Fluctuation	ICU admission serum sodium was recorded and compared with the absolute maximum change in serum sodium during the ICU stay (Marshall et al.,(²¹) Eagles et al.,(⁸) Sakr et al.(²²)) Highest minus lowest serum sodium values during ICU admission were taken (Bales et al.,(¹⁴) Jin et al.,(¹⁹) Harada et al.,(⁹) Labib et al.)(²⁰)
Variability	Quantified using measured standard deviation (Harrois et al.(¹⁰), Cohen et al.)(⁷) Quantified using measured coefficient of variation (standard deviation divided by the mean and x 100) (Sen et al.,(²³) Chua et al.)(¹⁵)

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[TFN1] mRS - modified Rankin score; ICU - intensive care unit; LOS - length of stay; DCI - delayed cerebral ischemia; N/A - not applicable; aSAH - aneurysmal subarachnoid hemorrhage; SVS - symptomatic vasospasm.