105. A 70 year old male is admitted to the hospital with a left hemiparesis and altered consciousness. He is on aspirin 75 mg OD, atrovostatin 10mg OD and glibenclamide 15mg daily. His wife says he has been unwell for a couple of days and he has been off food. He has however, still been giving him all his medications. Which of the following tests is going to be most useful in finding a immediately reversible cause for his symptoms