Blood transfusion is very often done in perioperative period for neurosurgical cases. Blood transfusion is not devoid of adverse reactions. Numerous criteria for blood transfusion have been published by various scientific societies with respect to neurosurgical cases. Literature of using physiological parameters as transfusion triggers in neurosurgical cases is limited. This study attempts to observe for change in oxygen extraction ratio following blood transfusion. Also, duration of ICU stay and Modified Rankin score will be noted. Postoperative neurosurgical patients admitted in neurocritical care unit requiring blood transfusion will be included in the study. Basic vital parameters like heart rate (HR), blood pressure (BP), saturation of peripheral oxygenation (SpO₂), temperature will be noted from the monitor.  Haemoglobin, saturation of arterial oxygenation (Sa02), partial pressure of oxygen (Pa02), lactate and central venous oxygen saturation (ScVO₂)will collected from the blood gas analysis report before transfusion. The same parameters will be collected 15mins after transfusion.  Total length of ICU stay in days will be noted and Modified Rankin Score at discharge will be recorded. Pre and post transfusion data will be compared and analysed in 56 patients using paired t tests.