The impact of hormonal dynamics and serum sodium fluctuations on symptomatic vasospasm after subarachnoid hemorrhage

Hyponatremia Incidence After Subarachnoid Hemorrhage and Association with Outcomes: Systematic Review and Meta-Analysis

OBJECTIVE

Hyponatremia after aneurysmal subarachnoid hemorrhage (aSAH) is common; however, the incidence, and association with vasospasm, morbidity, and mortality, has yet to be defined. We aimed to identify incidence of hyponatremia after aSAH, and quantify its association with measurable outcomes.

METHODS

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant systematic review and meta-analysis was conducted (international prospective register of systematic reviews ID CRD42022363472). Articles published in MEDLINE, Embase, and Cochrane Library between January 1990 and January 2024 were included. Hyponatremia definitions, incidence during admission, and association among vasospasm, length of hospital stay, and poor outcome (Glasgow Outcome Scale 3 or less) were identified. Pooled incidence rates and binary and continuous outcomes were calculated using random effects meta-analysis models.

RESULTS

In total, 52 studies (10,512 patients) were included. Most studies included patients admitted to tertiary neuroscience centers (61.5%, N = 32), or critical care units (23.1%, N = 11). Sodium of less than 135 mmol/L was the most commonly used hyponatremia definition (84.6%, N = 44). The pooled incidence of hyponatremia was 37.0% (95% confidence interval [CI]: 31.7%-42.4%). Hyponatremia increased the risk of vasospasm (15 studies; odds ratio: 2.93; 95% CI: 1.77-4.84), and length of hospital stay (3 studies, 16.4 days vs. 8.0 days, mean difference 8.5 [95% CI: 4.6-12.4]), but was not associated with poor outcome (10 studies; odds ratio 1.15; 95% CI 0.44-3.02). These findings remained when carrying out sensitivity analysis for different hyponatremia and outcome definitions, bias, and aSAH populations.

CONCLUSIONS

Hyponatremia is common in aSAH, may increase the likelihood of vasospasm, but in isolation does not appear to affect overall outcomes. Managing hyponatremia effectively should be a priority for treating clinicians.

The impact of serum sodium variability on surgical patients with aneurysmal subarachnoid hemorrhage

Currently, limited evidence exists on the impact of serum sodium variability in patients with aneurysmal subarachnoid hemorrhage (SAH) who underwent surgical clipping. We aimed to perform a detailed examination of the relationship between sodium variability and mortality in these patients. We conducted a cohort study including adult patients with aneurysmal SAH who underwent surgical clipping at a university hospital. Propensity score matching (PSM) was used to match patients' baseline characteristics. We evaluated the association between serum sodium standard deviation and mortality. Net reclassification improvement was calculated to assess and compare the reclassification capacity of different models. Trends in serum sodium over time were detected using linear mixed-effects models. Of 563 aneurysmal SAH patients who underwent surgical clipping during the study period, the average age was 56.87 ± 10.81 years. The serum sodium standard deviation was 4.24 [2.65-5.82] mmol/L. Patients with high sodium variability had significantly higher odds of mortality (adjusted odds ratio [aOR]: 1.93, 95% confidence interval [CI]: 1.01 to 3.68; P = 0.045). PSM analysis showed similar results (aOR: 2.23, 95% CI: 1.10 to 4.99; P = 0.045). Additionally, an increase in serum sodium of more than 5 mmol/L was significantly associated with mortality (aOR: 3.46, 95% CI: 1.26 to 9.20; P = 0.016) in a linear dose-response pattern. High serum sodium variability and an increase in serum sodium of more than 5 mmol/L were independent predictive factors of mortality in aneurysmal SAH patients who underwent surgical clipping. Thus, even mild changes in sodium levels warrant close attention.

Sodium and Its Impact on Outcome After Aneurysmal Subarachnoid Hemorrhage in Patients With and Without Delayed Cerebral Ischemia

OBJECTIVES

To perform a detailed examination of sodium levels, hyponatremia and sodium fluctuations, and their association with delayed cerebral ischemia (DCI) and poor outcome after aneurysmal subarachnoid hemorrhage (aSAH).

DESIGN

An observational cohort study from a prospective SAH Registry.

SETTING

Tertiary referral center focused on SAH treatment in the Amsterdam metropolitan area.

PATIENTS

A total of 964 adult patients with confirmed aSAH were included between 2011 and 2021.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 277 (29%) developed DCI. Hyponatremia occurred significantly more often in DCI patients compared with no-DCI patients (77% vs. 48%). Sodium levels, hyponatremia, hypernatremia, and sodium fluctuations did not predict DCI. However, higher sodium levels were significantly associated with poor outcome in DCI patients (DCI onset -7, DCI +0, +1, +2, +4, +5, +8, +9 d), and in no-DCI patients (postbleed day 6-10 and 12-14). Also, hypernatremia and greater sodium fluctuations were significantly associated with poor outcome in both DCI and no-DCI patients.

CONCLUSIONS

Sodium levels, hyponatremia, and sodium fluctuations were not associated with the occurrence of DCI. However, higher sodium levels, hypernatremia, and greater sodium fluctuations were associated with poor outcome after aSAH irrespective of the presence of DCI. Therefore, sodium levels, even with mild changes in levels, warrant close attention.

Association between serum sodium levels within 24 h of admission and all-cause mortality in critically ill patients with non-traumatic subarachnoid hemorrhage: a retrospective analysis of the MIMIC-IV database

Objective

The study aimed to evaluate the relationship between serum sodium and mortality in critically ill patients with non-traumatic subarachnoid hemorrhage.

Methods

This is a retrospective investigation of critically ill non-traumatic patients with subarachnoid hemorrhage (SAH) utilizing the MIMIC-IV database. We collected the serum sodium levels at admission and determined the all-cause death rates for the ICU and hospital. We employed a multivariate Cox proportional hazard regression model and Kaplan-Meier survival curve analysis to ascertain the relationship between serum sodium and all-cause mortality. In order to evaluate the consistency of correlations, interaction and subgroup analyses were also conducted.

Results

A total of 864 patients with non-traumatic SAH were included in this study. All-cause mortality in the ICU and hospital was 32.6% (282/864) and 19.2% (166/864), respectively. Sodium levels at ICU admission showed a statistically significant J-shaped non-linear relationship with ICU and hospital mortality (non-linear P-value < 0.05, total P-value < 0.001) with an inflection point of ~141 mmol/L, suggesting that mortality was higher than normal serum sodium levels in hypernatremic patients. Multivariate analysis after adjusting for potential confounders showed that high serum sodium levels (≥145 mmol/L) were associated with an increased risk of all-cause mortality in the ICU and hospital compared with normal serum sodium levels (135-145 mmol/L), [hazard ratio (HR) = 1.47, 95% CI: 1.07-2.01, P = 0.017] and (HR = 2.26, 95% CI:1.54-3.32, P < 0.001). Similarly, Kaplan-Meier (K-M) survival curves showed lower survival in patients with high serum sodium levels. Stratified analysis further showed that the association between higher serum sodium levels and hospital all-cause mortality was stronger in patients aged < 60 years with a hospital stay of <7 days.

Conclusion

High serum sodium levels upon ICU admission are related to higher ICU and hospital all-cause mortality in patients with non-traumatic SAH. A new reference is offered for control strategies to correct serum sodium levels.