• Fritz-Patrick Jahns, John Paul Miroz, Mahmoud Messerer, Roy T Daniel, Fabio Silvio Taccone, Philippe Eckert, and Mauro Oddo.
• Department of Intensive Care Medicine, Centre Hospitalier Universitaire Vaudois (CHUV), Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 46, BH 08.623, CH-1011, Lausanne, Switzerland.
• Crit Care. 2019 May 2; 23 (1): 155.

BackgroundElevated intracranial pressure (ICP) is frequent after traumatic brain injury (TBI) and may cause abnormal pupillary reactivity, which in turn is associated with a worse prognosis. Using automated infrared pupillometry, we examined the relationship between the Neurological Pupil index (NPi) and invasive ICP in patients with severe TBI.MethodsThis was an observational cohort of consecutive subjects with severe TBI (Glasgow Coma Scale [GCS] < 9 with abnormal lesions on head CT) who underwent parenchymal ICP monitoring and repeated NPi assessment with the NPi-200® pupillometer. We examined NPi trends over time (four consecutive measurements over intervals of 6 h) prior to sustained elevated ICP > 20 mmHg. We further analyzed the relationship of cumulative abnormal NPi burden (%NPi values < 3 during total ICP monitoring time) with intracranial hypertension (ICHT)-categorized as refractory (ICHT-r; requiring surgical decompression) vs. non-refractory (ICHT-nr; responsive to medical therapy)-and with the 6-month Glasgow Outcome Score (GOS).ResultsA total of 54 patients were studied (mean age 54 ± 21 years, 74% with focal injuries on CT), of whom 32 (59%) had ICHT. Among subjects with ICHT, episodes of sustained elevated ICP (n = 43, 172 matched ICP-NPi samples; baseline ICP [T- 6 h] 14 ± 5 mmHg vs. ICPmax [T0 h] 30 ± 9 mmHg) were associated with a concomitant decrease of the NPi (baseline 4.2 ± 0.5 vs. 2.8 ± 1.6, p < 0.0001 ANOVA for repeated measures). Abnormal NPi values were more frequent in patients with ICHT-r (n = 17; 38 [3-96]% of monitored time vs. 1 [0-9]% in patients with ICHT-nr [n = 15] and 0.5 [0-10]% in those without ICHT [n = 22]; p = 0.007) and were associated with an unfavorable 6-month outcome (15 [1-80]% in GOS 1-3 vs. 0 [0-7]% in GOS 4-5 patients; p = 0.002).ConclusionsIn a selected cohort of severe TBI patients with abnormal head CT lesions and predominantly focal cerebral injury, elevated ICP episodes correlated with a concomitant decrease of NPi. Sustained abnormal NPi was in turn associated with a more complicated ICP course and worse outcome.

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