CD4 and delirium: Stress response indexes [cortisol (Cor), blood glucose (Glu), adrenaline (E), noadrenaline (NE)], T lymphocyte subsets (CD3+, CD4+, CD8+, CD4+/CD8+), inflammatory indexes [tumor necrosis factor -α (TNF-α) and interleukin-6 (IL-6)] were detected before and after operation, and the incidence of postoperative delirium in both groups was recorded.