Association of Post-Procedural Serum Sodium with 90-Day Mortality in Acute Ischaemic Stroke Patients Undergoing Mechanical Thrombectomy: A Retrospective Single-Centre Observational Study.

Background/Objectives: Electrolyte disturbances are common in patients with Acute Ischemic Stroke (AIS) and may influence clinical outcomes. However, the prognostic significance of peri-procedural electrolyte changes in patients undergoing mechanical thrombectomy remains insufficiently investigated. This study aimed to evaluate the associations of pre- and post-procedural serum electrolyte levels and peri-procedural electrolyte changes with 90-day mortality in patients with AIS treated with mechanical thrombectomy. Methods: This retrospective observational study included 274 adult patients with anterior circulation large-vessel occlusion who underwent mechanical thrombectomy between February 2017 and February 2026. Serum sodium (Na), potassium (K), chloride (Cl), and calcium (Ca) levels were recorded before thrombectomy and within the first hour after the procedure. Peri-procedural electrolyte changes (Δ) were calculated as post-procedural minus pre-procedural values. Clinical, imaging, laboratory, and procedural variables associated with 90-day mortality were evaluated using univariate and multivariable logistic regression analyses. Results: Of the 274 patients, 67 (24.5%) died within 90 days. Post-procedural serum Na levels were significantly lower in the mortality group than in the survival group (p = 0.030). No significant associations were observed between 90-day mortality and pre-procedural electrolyte levels or peri-procedural electrolyte changes. In the multivariable analysis, higher admission National Institutes of Health Stroke Scale (NIHSS) scores (p = 0.001), symptomatic intracranial hemorrhage (p < 0.001), higher admission glucose levels (p = 0.003), and higher triglyceride levels (p = 0.046) were independently associated with increased 90-day mortality, whereas successful reperfusion (TICI 2b-3) (p = 0.011) and higher post-procedural serum Na levels (OR = 0.851, 95% CI: 0.749-0.968; p = 0.014) were independently associated with reduced odds of 90-day mortality. The addition of post-procedural serum Na to the base model resulted in a modest increase in discrimination (AUC 0.800 to 0.812; ΔAUC = 0.012), which was not statistically significant (DeLong p = 0.454). Conclusions: Among the peri-procedural electrolyte parameters evaluated, only post-procedural serum Na was independently associated with 90-day mortality after mechanical thrombectomy. However, adding post-procedural serum Na to established clinical, procedural, and metabolic predictors did not significantly improve model discrimination. These findings suggest that post-procedural serum Na may represent an associated prognostic marker, while its incremental predictive utility beyond established predictors remains unproven.