Dexamethasone 0.5ug/kg group:After induction, dexmedetomidine 0.5ug/kg was administered 10min before headpinning, and the intravenous drip was completed within 10min.

Canceled by the investigator. The effect of frontal infiltration and intravenous dexmedetomidine on the stress factors and haemodynamic response to skull-pin placement for craniotomy

The effect of dexmedetomidine and local infiltration on the haemodynamic and stress response and to skull-pin placement for craniotomy