Using NIRS-Based Spectroscopy for the Comparison of Cerebral Net-Water Uptake and Microcirculation in Posttraumatic Penumbra in Severe Traumatic Brain Injury Patients.

Purpose: The aim of our study was to compare net-water uptake (NWU), which serves as a quantitative imaging marker of cerebral edema, with brain oxygen status and cerebral microcirculation changes in posttraumatic peri-ischemic foci (PIF) in severe traumatic brain injury (sTBI) patients.

Materials And Methods: 89 sTBI patients (women 35; men 54, age 37 years [25;47]) with unilateral frontal/frontotemporal lesions were included in this retrospective, non-randomized, single-center study. Cerebral blood flow (CBF), cerebral blood volume (CBV), delay time (DT), time to maximum contrast concentration (Tmax), and mean transit time (MTT) were measured in PIF and determined using dynamic perfusion computed tomography (PCT) in the first 2 days after trauma and admission. NWU in PIF was calculated using non-contrast CT. Cerebral oxygenation (SctO) was simultaneously measured using near-infrared spectroscopy (NIRS) in the frontal lobes after PCT. Data are shown as a median (interquartile range). Statistical analysis was performed using nonparametric statistics. p<0.05 was considered statistically significant.

Results: Penumbra/core ratio median (mismatch ratio) was 2.12 (1.78; 2.87). In PIF, SctO median was 61.2% (56.6;64.3), CBF median was 21.4mL/100g/min (18.4; 27.7), CBV median was 1.9mL/100g (1.7; 2.3), MTT median was 6.2 s (4.5;7.9), DT median was 2.7 s (1.7;3.3) and NWU median was 7.22% (3.23;12.39). We divided all patients into a group with NWU >7.22% ("high" NWU) and a group with NWU below 7.22% ("low" NWU). The division was done according to the median level in the overall cohort; however, it was statistically significant in NWU (median 4.5% [3.33;6.47] vs. 11.78% [10.46;13.00], p<0.001, respectively). The differences between "low" NWU and "high" NWU groups were statistically significant in SctO, CBF, CBV, and T (p<0.001). Therefore, in the "high" NWU group, CBF and CBV in PIF were significantly lower, SctO was significantly higher, and T was more prolonged than in the PIF of the "low" NWU group. Correlation analysis showed the presence of significant relationships in both groups between NWU and CBF, SctO and DT (p<0.001).

Conclusion: Brain edema in PIF was significantly associated with cerebral microcirculation and cerebral O saturation disturbances in patients with sTBI.