Inflammation Connected to Onset of Delirium

Results from a recent study showed that elevated levels of inflammatory markers were strongly associated with delirium in post-surgical patients.

Millions of older Americans experience delirium following surgery or serious illness, adding additional complications to their hospital stays; however, the role of inflammation in delirium onset was poorly understood until recently. Previous research analyzed inflammatory markers but the results could only go so far since it was only able to examine one cytokine at a time. Researchers from Beth Israel Deaconess Medical Center (BIDMC) utilized another method to uncover the connection between the conditions.

“Inflammation is a complicated phenomenon, and we wanted a complete picture of what was taking place,” co-senior author George Kuchel, MD, said in a news release. “We needed to simultaneously measure multiple cytokines in order to evaluate networks of inflammatory pathways.”

The team gathered data from 566 adults at least 70 years old undergoing noncardiac surgery. From there they were able to analyze 12 cytokines at four different points: prior to surgery (baseline), immediately after surgery, postoperative day 2, and postoperative day 30. After taking baseline cognition into consideration, along with age, sex, surgery type, vascular comorbidity, and Apolipoprotein E genotype, the researchers identified delirium-associated cytokines. Out of the participants, 24% had delirium.

Two days following surgery, patients with delirium had significantly higher levels of the inflammatory marker interleukin-6 (IL-6), according to SAGES (Successful Aging after Elective Surgery Study) published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences. In addition, those patients also showed elevated levels of interleukin 2 (IL-2).

“The magnitude of difference in levels of IL-6 between delirious and non-delirious patients was about 10 times the upper limit for normal levels in older adults,” confirmed co-lead author Sarinnapha M. Vasunilashorn, PhD.

The authors noted that while the IL-6 elevation was observed two days after surgery the same could not be said on day 30. Therefore, another opportunity of study may be to determine the persistence of delirium and where the inflammatory markers come into play. However, the findings still provide a stepping stone to identifying patients most at risk for delirium.

“With strong evidence for the involvement of IL-6 and evidence for the involvement of IL-2 in patients with delirium, it appears that inflammation is indeed a basic mechanism underlying this condition,” concluded co-senior author Edward Marcantonio, MD.