The incidence of cerebral vasospasm after aneurysm subarachnoid hemorrhage (aSAH) is as high as 70%; cerebral vasospasm（CVS） is closely related to delayed cerebral ischemia （DCI）, which is one of the important reasons for poor outcomes in patients with aSAH.

In recent years, it has been reported that stellate ganglion block(SGB) can effectively alleviate cerebral vasospasm(CVS), reduce cerebral blood flow velocity and increase cerebral perfusion in patients with aneurysm subarachnoid hemorrhage(aSAH)。However, whether the alleviation of CVS after SGB is beneficial to the long-term neurological prognosis has not been confirmed Therefore, a prospective randomized controlled study is needed to further explore the role of SGB block in improving the outcomes of patients with aSAH.

Inclusion Criteria:

• Age range: 18-65 years old;
• Within 72 hours after onset of aSAH,and planning surgical treatment(aneurysm embolizing or clipping);
• Preoperative Hunt-Hess grade 2-3
• Sign informed consent.

Exclusion Criteria:

• ASA > grade IV;
• Patients with posterior circulation aneurysm;
• Patients with severe systemic hemorrhagic diseases;
• Patients with trauma and local infection in the nerve block area;
• Local anatomic structure changes (neck structure changes caused by radiotherapy, chemotherapy and surgery);
• Allergy to known local anesthetics;
• Pregnant and lactating women.