Pain management Severe headache can be present with SAH and is caused by irritation from blood in the subarachnoid space and raised ICP . The importance of treating pain cannot be overemphasised as the distress it can cause significantly increases ICP and exacerbates the potential of secondary injury through rebleeding. Paracetamol, codeine-based drugs and morphine can be used to promote sleep and to calm agitation. Mrs S was commenced on a fentanyl infusion along with her sedation. However, at times she was agitated, restless and distressed, so codeine phosphate was administered to allow her to became more settled.