Effects of apolipoprotein E polymorphism on cerebral oxygen saturation, cerebral perfusion, and early prognosis after traumatic brain injury

OBJECTIVE: To investigate the effects of the apolipoprotein E (APOE) gene on oxygen saturation and cerebral perfusion in the early stages of traumatic brain injury (TBI). METHODS: This study included 136 consecutive TBI patients and 51 healthy individuals. The APOE genotypes of all subjects were determined using quantitative fluorescence polymerase chain reaction (QF‐PCR). Regional cerebral oxygen saturation (rScO2) of patients with TBI and normal subjects was monitored using near‐infrared spectroscopy (NIRS). Computed tomography (CT) perfusion was used to obtain cerebral perfusion in patients with TBI and normal subjects. RESULTS: In the TBI group, the rScO2 of APOEε4 carriers (53.06 ± 6.87%) was significantly lower than that of non‐carriers (58.19 ± 5.83%, p < 0.05). Meanwhile, the MTT of APOEε4 carriers (6.75 ± 1.30 s) was significantly longer than that of non‐carriers (5.87 ± 1.00 s, p < 0.05). Furthermore, correlation analysis showed a negative correlation between rSCO2 and MTT in patients with TBI. Both the univariate and multifactorial logistic regression analyses revealed that APOE ε4, hypoxia, MTT >5.75 s, Marshall CT Class, and GCS were independent risk factors for early poor prognosis in patients with TBI. CONCLUSION: Both cerebral perfusion and cerebral oxygen were significantly impaired after TBI, and low cerebral perfusion and hypoxia were related to poor prognosis of patients with TBI. Compared with APOE ε4 non‐carriers, APOE ε4 carriers not only had poorer cerebral perfusion and cerebral oxygen metabolism but also worse prognosis in the early stages of TBI. Furthermore, a negative correlation was observed between the rSCO2 and MTT levels. In addition, both CT perfusion scanning (CTP) and NIRS are reliable for monitoring the condition of patients with TBI in the neurological intensive care unit (NICU).