Patient's baseline cerebrospinal fluid (CSF) and serum blood sample will be collected. The baseline CSF will be collected via an indwelling lumbar subarachnoid catheter placed prior to intervention as a modality to prevent the complication associated with SAH like vasospasm and to facilitate the drainage of SAH. A venipuncture will be done and 2 to 3 ml of blood sample will be collected in plain vial for serum/EDTA for plasma.The second CSF and serum blood sample will be collected after 1 hours of exposure to anaesthesia. The third sample will be collected following completion of intervention or after the cessation anesthetic agent, whichever is earlier.