Abstract: Objective To observe the effects of perineural and intravenous dexmedetomidine injection combined with scalp nerve block on perioperative hemodynamics and stress response.Methods Elective intracranial aneurysm surgery for 50 patients，which were randomly divided into two groups（n=25）：DEX 1ug/kg intravenous injection group（group A）and DEX 1ug/kg mixed with ropivacaine perineural group（group B）.Patients in both groups were treated with bilateral scalp nerve block guided by ultrasound.Endotracheal intubation was performed after general anesthesia induction.Mean arterial pressure（MAP）and heart rate（HR）at pre-induction（T0），5min after intubation（T1），incision（T2），sawing skulls（T3）and the end of surgery（T4）were recorded，blood cortisol levels at T0，T2 and 6h after surgery（T5）were recorded.Intraoperative propofol and remifentanil consumption、duration of analgesia and number of patients requiring rescue analgesia were recorded.Results The MAP of T1 ~ T4 in both groups was lower than that at T0.In group A，HR at all time points from T1 to T4 decreased compared with that at T0，HR in group B was only lower than T0 at T1 and T4（P<0.05）.MAP at T1，T2 and HR at T1，T2，T3 in group B were statistically different from those in group A（P<0.05）.Blood cortisol level at T5 in group B（378.6nmol/L）was significantly decreased compared with group A（429.4nmol/L）（P<0.05）.Duration of postoperative analgesia in group B（736.4min）was prolonged compared with group A（652.8min），while only one patient in group B needed relief compared with group A.（both P<0.05）.Conclusion Compared with intravenous administration，perineural dexmedetomidine combined with scalp nerve block can stabilize hemodynamics，prolong postoperative analgesia duration and reduce perioperative stress response.

Key words: dexmedetomidine, scalp nerve block, hemodynamics, stress response