B54-37 Ultrasonographic Optic Nerve Sheath Diameter as a Marker of Intracranial Pressure Response to Osmotherapy: A Systematic Review and Meta-analysis

Rationale Ultrasonographic measurement of the optic nerve sheath diameter (ONSD) has emerged as a bedside, noninvasive surrogate of intracranial pressure (ICP), particularly when invasive monitoring is unavailable or contraindicated. Despite its growing use, the extent to which ONSD reliably reflects the physiological response to osmotherapy remains uncertain, limiting its clinical utility for therapeutic monitoring. To address this gap, we conducted a systematic review and meta-analysis to quantify short-term changes in ONSD after osmotic therapy in adults with traumatic or acute brain injury and to evaluate the robustness of the available evidence. Methods This review was prospectively registered in PROSPERO (CRD420250651964) and conducted in accordance with PRISMA 2020 guidelines. We systematically searched MEDLINE, EMBASE, Scopus, Web of Science, Cochrane Library, and Google Scholar through October 2024 without language restrictions. Eligible studies included adults with intracranial hypertension secondary to traumatic or acute brain injury who received osmotherapy (mannitol or hypertonic saline) and had ONSD measured by ultrasound before and after treatment. Two reviewers independently screened studies, extracted data, and assessed risk of bias using ROBINS-I. The primary outcome was the pre-post mean difference (MD) in ONSD. Random-effects meta-analysis was performed using restricted maximum likelihood estimation. When necessary, means and standard deviations were derived from medians or other summaries, and SDs of change were imputed from within-person correlations. Results Four observational studies (n = 313) met the inclusion criteria. Osmotherapy consisted exclusively of intravenous mannitol, typically 0.5-0.86 g/kg. Most studies reassessed ONSD within 20-60 minutes after administration. The pooled analysis showed a mean ONSD reduction of − 0.39 mm (95% CI − 0.74 to − 0.04; p = 0.001) approximately 60 minutes after osmotherapy. Between-study heterogeneity was very high (I² = 96.2%, p < 0.001). The overall risk of bias was moderate to high, and the certainty of evidence was rated as low to very low. Conclusion Ultrasound-measured ONSD decreases slightly after osmotherapy, suggesting potential value as a noninvasive adjunct for tracking ICP dynamics but not as a substitute for invasive monitoring. The small and inconsistent effect, coupled with limited evidence, underscores major research gaps. Standardized, operator-independent protocols calibrated to invasive ICP and studies including broader populations are needed to determine whether ONSD can become a reliable, protocolized bedside tool. This abstract is funded by: None