Association between optic nerve sheath diameter and mortality in patients with severe traumatic brain injury.

PURPOSE Increased intracranial pressure (ICP) is associated with worse outcomes following traumatic brain injury (TBI). Studies have confirmed that ICP is correlated with optic nerve sheath diameter (ONSD) on ultrasound. The aim of our study was to assess the independent relationship between ONSD measured using CT and mortality in a population of patients admitted with severe TBI. METHODS We conducted a retrospective cohort study of patients with a TBI requiring ICP monitoring admitted to the ICU between April 2006 and May 2012 to two neurotrauma centers. ONSD was independently measured by two physicians blinded to patient outcomes. Multivariable logistic regression modeling was used to assess an association between ONSD and hospital mortality. RESULTS A total of 220 patients were included in the analysis. Overall, the cohort had a mean age of 35 (SD 17) years and 171 of 220 (79 %) were male. The median admission GCS was 6 (IQR 3-8). Intra-class correlation coefficient between raters for ONSD measurements was 0.92 (95 % CI 0.90-0.94, P < 0.0001). On multivariable analysis, each 1 mm increase in ONSD was associated with a twofold increase in hospital mortality (OR 2.0, 95 % CI 1.2-3.2, P = 0.007). Using linear regression, ONSD was independently associated with increased ICP in the first 48 h after admission (β = 4.4, 95 % CI 2.5-6.3, P < 0.0001). CONCLUSIONS In patients with TBI, ONSD measured on CT scanning was independently associated with ICP and mortality.