Assessment of the Optic Nerve Sheath Diameter by Bedside Sonography and Its Correlation With the Glasgow Coma Score in the Outcome of Patients With Sepsis-Associated Encephalopathy

Abstract

Background: Sepsis-associated encephalopathy (SAE) is an acute diffuse cerebral dysfunction occurring in patients with sepsis in the absence of direct central nervous system infection or another primary neurological disorder. Ultrasonographic measurement of the optic nerve sheath diameter (ONSD) has been proposed as a non-invasive surrogate marker of elevated intracranial pressure. This study evaluated the association of serial ONSD measurements with Glasgow Coma Scale (GCS) scores and clinical outcomes in patients with SAE. Materials and methods: This prospective observational study was conducted in the Intensive Care Unit (ICU) of Indraprastha Apollo Hospitals, New Delhi, from May 2021 to October 2022. The study included 80 patients, aged ≥18 years, who were admitted to the ICU with SAE. ONSD and GCS scores were measured by bedside USG at the time of diagnosis of SAE (0 hrs), at 24 hours, 72 hours, on the fifth day, or when any clinical deterioration of the patient is evident. Outcomes measured were 28-day mortality, duration of ICU and hospital stays. Data thus collected were subjected to statistical analysis, and results were drawn. Results: The mean age of the patients was 53.24 ± 13.20 years, and 42 patients (52.5%) were male. The mean Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores were 19.54 ± 3.33 and 9.32 ± 2.36, respectively. No statistically significant correlations were observed between ONSD and GCS scores at baseline, 24 hours, 72 hours, day 5, or the time of clinical deterioration. The baseline ONSD was not significantly correlated with the APACHE II score, SOFA score, ICU length of stay, or hospital length of stay. Twelve patients (15%) died within 28 days. The mean baseline ONSD was higher among non-survivors than among survivors (5.35 ± 0.19 versus 5.20 ± 0.23 mm; p=0.035). However, when the ONSD was dichotomized using a threshold of 5.5 mm, mortality was not significantly different between patients with elevated and normal ONSD values (30.0% versus 12.9%; p=0.16). No significant differences in ICU or hospital length of stay were identified according to the ONSD category. Conclusion: Serial ONSD measurements were not significantly correlated with GCS scores, disease-severity scores, or length-of-stay outcomes in this cohort of patients with SAE. Although the mean baseline ONSD was higher among non-survivors, this finding was not reproduced when the ONSD was categorized using a 5.5-mm threshold and should therefore be considered exploratory. Larger studies using standardized ONSD protocols and adjusted longitudinal analyses are required.