Correlation between Post-Craniotomy Decrease in Optic Nerve Sheath Diameter and the Duration of Ventilator Support in Supratentorial Tumor Patients: A Prospective Observational Study

Background: Post-craniotomy intracranial pressure (ICP) monitoring guides intensive care management. Optic nerve sheath diameter (ONSD) measured by transorbital ultrasonography is a noninvasive ICP surrogate. The relationship between perioperative ONSD reduction and mechanical ventilation duration has not been clearly established. The aim of this study is to evaluate the correlation between post-craniotomy ONSD reduction and mechanical ventilation duration in patients undergoing supratentorial tumor resection. Materials and Methods: A prospective observational cohort study conducted from October 2025 to January 2026 included 60 adults (American Society of Anesthesiologists physical status I–II, aged 18–65 years) undergoing elective supratentorial craniotomy. ONSD was measured bilaterally 3 mm posterior to the retina before and at the end of surgery. The primary outcome was ventilation duration (hours from intensive care unit admission to extubation). Spearman’s correlation was used to assess the relationship between ONSD and ventilation duration. Results: Mean age was 46.73 ± 6.59 years; 53.3% were female. Median ventilation duration was 8 h (interquartile range [IQR]: 4.0–14.0; range: 2–168); 55 patients (91.7%) required ventilation <24 h, while 5 (8.3%) required ≥24 h. The distribution was markedly right-skewed (mean: 12.12 ± 21.46 h), reflecting strong outlier influence. ONSD reduction (ΔONSD) correlated negatively with ventilation duration (right eye: r = −0.590, P < 0.001; left eye: r = −0.419, P = 0.001). End-of-surgery ONSD correlated positively (right eye: r = 0.421, P = 0.001; left eye: r = 0.533, P < 0.001). Conclusions: Greater ONSD reduction post-craniotomy was associated with shorter mechanical ventilation. Bilateral ONSD measurement may provide complementary information for perioperative risk stratification in selected elective patients, pending validation with multivariable analysis and external replication. ONSD should be considered an adjunctive tool rather than a standalone decision criterion for extubation.