Objective:To investigate the clinical efficacy of dexmedetomidine in the regulation of TLR4/My D88/NF-κB in the prevention of paroxysmal sympathetic over-excitation (PSH) in patients with severe head injury. Methods:One hundred patients with severe head injury who were admitted to our hospital from September 2016 to May 2019 were enrolled. The randomized digital table method was divided into 50 cases in the study group and the control group. Patients in the study group were given dexmedetomidine at a dose of 1.0 μg/kg before anesthesia induction, followed by infusion at 0.4 μg / (kg·h), and the control group was injected with the same amount of normal saline. The incidence of PSH, clinical symptoms, imaging findings, mechanical ventilation time, tracheal intubation/incision duration, ICU hospitalization time, total length of hospital stay, and GCS scores three months after discharge were compared between the two groups. At the same time, the fluorescence intensity, TLR4, NF-κB expression level and tumor necrosis factor-α (TNF-α) expression levels in peripheral blood CD14+ monocytes of the two groups were detected. Results:The incidence of PSH was significantly lower in the study group than in the control group at 7 and 3 months (P<0.05). The total length of hospital stay, duration of ICU hospitalization, intraoperative tracheotomy, and mechanical ventilation time were significantly lower in the study group than in the control group. And the GCS score was higher than the control group, and the difference was statistically significant (P<0.05). In addition, the imaging results showed that there were some differences in the location of imaging lesions between the two groups. The proportion of lesions in the ventricular system and surrounding areas was higher in the control group than in the study group (P<0.05). And the T14-T3 CD14+ PBMC MyD88 fluorescence intensity, TLR4 and NK-κB positive expression rate were significantly higher than those of T0 (P<0.05), but the MyD88 fluorescence intensity, TLR4 and NK-κB positive expression rate in the study group were significantly lower than those in the control group at T1～T3 (P<0.05). The levels of serum TNF-α in T1～T3 groups were significantly higher than those in T0 (P<0.05), but the levels of serum TNF-α in T1～T3 in the study group were significantly lower than those in the control group (P< 0.05). Conclusions:Dexmedetomidine can reduce the oxidative stress response in patients with severe head injury by inhibiting TLR4/My D88/NF-κB signaling pathway, thus effectively reducing the risk of PSH and improving the prognosis of patients.