Need input on a patient condition please.

Any input would be greatly appreciated to help save our patient.

Expreemie (less than 2 years old right now...don't want to get too specific because of HIPPA) with bilateral pulmonary vein stenosis, one side worse than the other. Most recent limited echo was stable. Trached and vented with moderate vent settings (PC + PS). Has had multiple ICU admissions for worsening respiratory distress, and has had multiple infections in the past. Recently treated for a UTI but still has blood/protein/casts in urine with a negative cx and no WBCs. Negative renal ultrasound and relatively negative CXR. Negative blood cultures and basically benign labs. Has been febrile for over a week straight, over 105 but mostly around 103. Was on dual abx coverage but stopped because there was no response. Minimal response to Tylenol (sometimes fever even increases) but some response to Motrin usually. Is MISERABLE. Cries when you go to touch them. Fever increases with agitation. Blood pressures have been trending higher, pt is usually 80s/40s and 50s. Has been 1-teens and 20s over 70s and 80s while asleep. The pt is not dry, BUN/cr was on the lower end and visually looks hydrated with good cap refill and turgor. Providers are thinking it's neuro with autonomic instability, but I just can't shake the feeling it's something else. I thought maybe an aseptic meningitis, but an LP is not warranted at this time. Pt had a fever > 106 at one point a couple of weeks ago and we were told it was because of a UTI, but has been febrile on and off since that point despite negative urine cx, and now febrile for over a week straight. What do you think? Any suggestion would be appreciated, we are all stumped by this case.