The association of chronic pain and postoperative delirium: a prospective observational cohort study

Postoperative delirium (POD) is an acute and common complication after surgery that can increase morbidity and mortality. Few previous studies with inconsistent findings have examined the association of preoperative pain and POD. Our purpose is to investigate the association of preoperative chronic pain and POD.

This prospective observational cohort study included 200 patients ≥ 18 years scheduled for elective surgery under general anaesthesia in a tertiary care hospital. POD was defined as meeting diagnostic criteria during the study visits (according to delirium screening tests and the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition), or by diagnosis of the responsible physicians. Chronic pain was defined as pain lasting six months or longer. Features of chronic pain were assessed with the German Pain Questionnaire, including the Depression Anxiety and Stress Scale-21 (DASS-21). Associations with POD were assessed using logistic regression analysis adjusting for confounding factors.

Thirty-nine (22%) out of 176 patients developed POD. Chronic pain was not associated with POD after adjustment for ASA physical status, duration of anesthesia and DASS-21 Anxiety score (Odds ratio [OR], 95%-Confidence Interval [CI], 2.216 [0.968;5.070], P=0.060). A subgroup analysis of chronic pain patients revealed that current pain intensity was higher in patients with POD.

Preoperative chronic pain was no independent predictor for POD. Current pain intensity was higher in chronic pain patients with POD. This indicates that certain features of pain might be influential. Further research is needed to examine different forms of preoperative pain and their possible influence on POD.