You are the haematology registrar on call and you get contacted regarding a 28 year old lady who presented to the A&E department on Saturday evening. She presented with a sudden onset severe headache that had been present for 12 hours with associated vomiting. Her CT Head has been provisionally reported over the phone to A&E as “normal” and  the medical registrar wants to perform an urgent lumbar punctureto investigate for possible subarachnoid haemorrhage.

Blood tests so far (Ref range in brackets):

Wcc 11.6 (3.6 – 11), Hb 140 (115-165), Plt 400 (140-400), Neu 10.2 (1.7-7.5)

PT 12.6 (10-14)

APTT 49 (22-36)

Fib 3 (1.5-4)

Is it safe to proceed with the planned lumbar puncture?

What other history would you ask the registrar on the phone?

Any further tests you would request from the lab?