I would not exclude that other stressors than neuroinflammation may play a role, including perioperative hypotension, perhaps in combination with hypoxia. Some interesting data seem to suggest that there may be a direct link between HYPOthermia and tau phosphorylation status. Ultimately it may be a mixture of several factors acting synergistically. Good luck!

I would recommend to read the following reviews on the topic:

http://www.ncbi.nlm.nih.gov/pubmed/23535147

http://www.ncbi.nlm.nih.gov/pubmed/21344011

http://www.ncbi.nlm.nih.gov/pubmed/19372347