Ultrasonographic optic nerve sheath diameter measurement for dynamic monitoring of intracranial pressure following osmotherapy

Background Patients with underlying intracranial pathology often develop elevated intracranial pressure (ICP). We assessed the utility of optic nerve sheath diameter (ONSD) measurement using point-of-care ultrasonography (POCUS) in patients with non-traumatic elevated ICP. Methods A prospective observational study was conducted amongst 80 patients, 18 years and above, recruited from AIIMS, New Delhi, over 2 years. Patients were divided into 5 etiopathological groups for analysis and interpretation which were infectious meningoencephalitis, metabolic encephalopathy, cerebrovascular accident, intracranial space-occupying lesions and other diagnosis. Based on their need for osmotherapy, patients with elevated ICP were divided into 4 groups: group 1 with hypertonic saline, group 2 with hypertonic saline and glycerol, group 3 with mannitol and group 4 with mannitol and glycerol. Statistical analysis was performed using STATA 16.0 version. Results In our study of 80 patients (aged > 18 years, mean age 38.58 ± 14 years), headache was the most common symptom (84%). Sequential ONSD measurements showed significant decrease after osmotherapy, with marked differences between groups. A statistically and clinically significant decrease in mean ONSD (overall) from 6.15 mm at baseline to 5.79 mm at 120 mins after osmotherapy (difference of 0.36 mm) was noted. Decrease in ONSD was statistically significant at 30 mins (difference of 0.14, p value < 0.05) and was clinically significant (difference of > 0.3 mm, p value < 0.05) from 60 mins onwards with further sustained decrease by 120 mins after osmotherapy. Patients with a Cushing response had varying ONSD decreases, with responders showing greater reductions, difference of 0.51 as compared to 0.24 in non-responders, (p value < 0.05). Conclusion The serial measurement of ONSD by POCUS is a rapid, non-invasive and feasible technique that can be performed by a clinician to assess response to osmotic therapy in a dynamic manner and thereby guide treatment.