Do stress markers and anesthetic technique predict delirium in the elderly?

Postoperative delirium (PD) is a prevalent complication of elderly surgical patients, which predisposes to worsened cognitive recovery and dementia. Risk of PD has been associated with increasing magnitude of the hypothalamic-pituitary-adrenal stress response (serum cortisol, epinephrine and norepinephrine) to surgery. Anesthetics suppress this response; however, some (total intravenous anesthesia, TIVA) more than others (anesthetic gases). Prior comparisons of anesthetics have been equivocal but have not included stress markers. We hypothesized that TIVA would decrease serum stress markers and the incidence of PD.

We performed a prospective cohort study of 76 elderly major surgical patients. Patients received TIVA or sevoflurane gas, and blood was drawn for serum markers pre-, intra-, and postoperatively. PD was assessed with the Confusion Assessment Method. We compared stress markers and PD between patients who received TIVA versus sevoflurane, and then modeled PD including stress and anesthetic.

The group that received TIVA during surgery demonstrated lower levels of all stress markers compared to the gas group, but no difference in PD. However, across groups, the postoperative norepinephrine level was much higher in patients who developed PD. Other markers and other times had no effect.

The development of PD depends more on postoperative stress than intraoperative stress or anesthetic.