Background and Purpose Dexmedetomidine has many benefits in perioperative administration. This study aims to describe the pharmacokinetics (PK) of intravenous, intranasal and oral administration of dexmedetomidine before anaesthesia induction, and evaluate the effects of dexmedetomidine on the visibility of the surgical field in tympanoplasty. Methods This single-blind, randomised controlled trial in a university-affiliated hospital. Forty-five patients underwent tympanoplasty under general anaesthesia were enrolled. Patients were randomly allocated, in blocks of 3, to dexmedetomidine by intravenous infusion at 0.8 μg.kg-1 for 10 min, intranasal instillation at a drop rate of 1 μg.kg-1, and oral intake at 4 μg.kg-1. PK of dexmedetomidine after a single low-dose administration and effect on the surgical field in tympanoplasty were analyzed. Results: A dexmedetomidine concentration of 220 pg/mL was achieved immediately after intravenous. infusion, and at 13.2 and 70.3 min for intranasal and oral administration, respectively. Dexmedetomidine decreased heart rate (HR) and MAP in all three groups, although these values remained higher in the oral dexmedetomidine group at all the eight time points. Intravenous dexmedetomidine provided the best visualisation of the surgical field for opening of the tympanic sinus, 30 min after the start of the infusion (P<0.05). Intranasal dexmedetomidine provided a significantly better visual field than oral dexmedetomidine for repair of a tympanic membrane perforation using the fascia temporal muscle ( P<0.05). Conclusion: A single low-dose of dexmedetomidine administered intravenously or intranasally can decrease HR and MAP and improve surgical field visibility, and appropriate for deliberate hypotension for surgical procedures 1-2 h in length.

Purpose：Chronic corneal pain is the most common symptom of dry eye disease (DED), while the central sensitization mechanisms underlying remain unclear. Methods：Excision of extra orbital lacrimal glands was used to establish dry eye (DE) model. Tear volume measurements, corneal fluorescein staining, corneal hypersensitivity and anxiety behavior were tested after surgery. The amplitude of low-frequency fluctuation (ALFF) by fMRI was used for determining brain functional activity. C-Fos, Brain-derived neurotrophic factor (BDNF), and cytokine levels in corresponding brain regions were tested. Results：Compared to the Sham group, the ALFF signals in the supplemental somatosensory area, secondary auditory cortex, agranular insular cortex, temporal association areas, and ectorhinal cortex brain areas were enhanced in DE group. ALFF signal in the insular cortex was related to corneal hypersensitivity (p < 0.01). C-Fos (P < 0.001), BDNF (P < 0.01), TNF-α, IL-6 and IL-1β (P < 0.05) increased, while IL-10 levels (P < 0.05) decreased in the insular cortex in the DE group. Surgery-induced corneal hypersensitivity and upregulation of inflammatory cytokines, but not anxiety, could be blocked by insular cortex injection of Tyrosine Kinase receptor B (TrkB) agonist cyclotraxin-B (P< 0.01). Conclusions ：This research presents the map of functional brain by ALFF through rs-fMRI associated with chronic corneal pain. BDNF-TrkB signaling-related neuroinflammation in the insular cortex might contribute to dry eye-related chronic corneal pain. This measure could potentially help clinicians improve therapeutic approach to pain control and development of diagnostic approach.