Aneurysmal subarachnoid hemorrhage (aSAH) is a common type of acute hemorrhagic stroke. One of its complications, cerebral vasospasm (CVS), is the main cause of death and disability, with an incidence of up to 30%-90%. Blood and its metabolites are vital reasons for CVS. Normal saline, as an intraoperative irrigation fluid for the surgery of aneurysm clipping, can induce secondary damage to the brain. In this study, a new type of magnesium-rich artificial cerebrospinal fluid (MACSF) has been designed, which has similar ionic concentration, pH value and osmotic pressure compared with the physiological cerebrospinal fluid. It has been confirmed by animal experiments that MACSF can relieve the hyper-responsiveness of cerebral arteries to ET and 5-HT induced by hemorrhagic CSF from patients with aSAH by down-regulating the expression of ETA, contractile ETB and 5-HT1B receptors in the previous research. Therefore, MACSF may have potential effects on preventing and treating CVS. In this study, we plan to apply MACSF as an intraoperative irrigation fluid for the surgery of aneurysm clipping (MACSF group), which is compared with normal saline (historical control group). To evaluate the effects of MACSF on reducing the incidence of CVS and improving the clinical prognosis of patients with aSAH, the occurrence of CVS within 14 days after aneurysm clipping, NIHSS score, as well as mRS scores at 1, 3 and 6 months after aSAH will be recorded and compared. CVS related biomarkers will be used to evaluate the relationship between the occurrence of CVS and the levels of biomarkers in both CSF and blood samples from MACSF group.

From now on, participants who meet the inclusion and exclusion criteria in our hospital will be recruited in the intervention group, if they and their relatives are willing to join in the study. For the historical control group, in which patients were treated by aneurysm clipping in Department of Neurosurgery of the First Affiliated Hospital of Xi'an Jiaotong University during the previous nine months, normal saline (0.9% Sodium Chloride Injection) was applied as intraoperative perfusion solution for their operation. For the intervention group, MACSF will be used. (The composition and concentration of MACSF is as follows: Na+: 146.2 mEq/l, K+: 2.7 mEq/l, Mg2+: 4.2 mEq/l, Cl-: 123 mEq/l, HCO3-: 23.2 mEq/l, Glucose: 0.75 g/l. MACSF is prepared by the staff of Pharmacy Intravenous Admixture Services of First Affiliated Hospital of Xi'an Jiaotong University, according to a specific formula in the specific working area. The whole procedure follow the aseptic principles strictly. Fresh-made MACSF will be placed in a specific container and send to the operating room through specific channels.) Then, for the patients who have signed the informed consent, blood (6ml) and CSF (3ml) samples will be collected during and every other day after the surgery for 14 days. The blood samples should be drawn into a non-anticoagulant tube and a heparin anticoagulant tube respectively. All the samples will be transferred to BioBank of the First Affiliated Hospital of Xi'an Jiaotong University in a liquid nitrogen tank. After re-melted in a water bath of 37℃, the CSF and blood samples will be centrifuged at 4℃ for 10min at 2000r/min, and then the supernatant will be collected and stored at -80℃. At the end of this study, the contents of NPY，MMP-9，MIF，TNF-α，Mg2+ and Ca2+in the samples will be detected by ELISA or mass spectrometry. Transcranial Doppler (TCD) will be observed within 14 days after the operation (daily for the first three days and every other day for the following days). CVS will be diagnosed by TCD, the diagnostic criteria will be described later. CT scan of the brain should be done at least once a week and rechecked anytime when necessary. If there is new low-density lesions, delayed cerebral infarction (DCI) will be diagnosed. The prognosis will be assessed at 1, 3 and 6 months after aSAH onset according to modified Rankin Scale (mRS) . Meanwhile, some indicators will be used to evaluate the safety of MACSF application, which incluiding secondary infection, fluctuation of intracranial pressure and hypermagnesemia. The diagnostic criteria and the solutions will be described in the next part.

Inclusion Criteria:

• Patient is between 18 and 80 years of old;
• aSAH is diagnosed by CTA, DSA or other cranial imaging examination;
• Patient is admitted to hospital within 72 hours after aSAH onset;
• Aneurysm is clipped within 36 hours after admission;
• Patient and his/her relatives are informed and agree to accept the above treatment plan.

Exclusion Criteria:

• Cause of the SAH is not rupture of an intracranial aneurysm;
• Time from SAH onset to admission is longer than 72 hours;
• Time from admission to surgery is longer than 36 hours;
• The patient dose not choose clipping;
• Patient has other serious diseases, such as heart failure, kidney failure, liver failure, etc;
• Patient or his/her relatives refuse to accept the above research plan.