A 32-year-old man presents to the Emergency Department with a sudden and severe headache that reached its peak intensity within seconds of onset. The pain is the worst he has ever experienced. The headache has been present for six hours but is now subsiding. He reports associated nausea, vomiting, and sensitivity to light.
The patient has no significant medical history and has never experienced a severe headache before. Upon examination, there are no notable findings. The casualty officer has already performed several tests, including a lumbar puncture, which was difficult and resulted in a bloody tap. A CT scan of the brain was normal, and the spinal fluid analysis showed 500 RBC/cm3, < 5 WBC/cm3, no organisms on Gram stain, and no xanthochromia. What is the next most important step in managing this patient?