I loved this book when i read it in the 1990s. "Fantastic Voyage II: Destination Brain".
In 1991 i was working far from home and a long train journey was necessary.. I was binge reading a whole collection of Isaac Asimov´s books to the level of obsession. (what better way to enjoy a subject?).So, the original "Fantastic Voyage" was a 1966 movie in which Asimov was hired to write a novelization. In that story a miniaturized ship with a full crew of scientist must dive in the bloodstream of a man to save him navigating in between several organs.
In 1987, Asimov wrote the sequel, which is a full self contained adventure on its own.In the (HIS) story, a miniaturized ship is inserted into a dying man´s bloodstream to save him, i mean, save a discovery he made, and they need to navigate his brain and rescue the info before he dies completely to death. I had a medical book about the brain beside me to understand all the biological terms and brain architecture, i felt like a scientist myself.
The catchphrase "The situation scalates quickly' surely applies to the story. If you find this book into a dusty bookstore, be sure to get your copy.