Association between postoperative delirium and postoperative cerebral oxygen desaturation in older patients after cardiac surgery

Abstract

Background: Near-infrared spectroscopy non-invasively measures regional cerebral oxygen saturation. Intraoperative cerebral desaturations have been associated with worse neurological outcomes. We investigated whether perioperative cerebral desaturations are associated with postoperative delirium in older patients after cardiac surgery. Methods: Patients aged 70 yr and older scheduled for on-pump cardiac surgery were included between 2015 and 2017 in a single-centre, prospective, observational study. Baseline cerebral oxygen saturation was measured 1 day before surgery. Throughout surgery and after ICU admission, cerebral oxygen saturation was monitored continuously up to 72 h after operation. The presence of delirium was assessed using the confusion assessment method for the ICU. Association with delirium was evaluated with unadjusted analyses and multivariable logistic regression. Results: Ninety-six of 103 patients were included, and 29 (30%) became delirious. Intraoperative cerebral oxygen saturation was not significantly associated with postoperative delirium. The lowest postoperative cerebral oxygen saturation was lower in patients who became delirious (P=0.001). The absolute and relative postoperative cerebral oxygen saturation decreases were more marked in patients with delirium (13 [6]% and 19 [9]%, respectively) compared with patients without delirium (9 [4]% and 14 [5]%; P=0.002 and P=0.001, respectively). These differences in cerebral oxygen saturation were no longer present after excluding cerebral oxygen saturation values after patients became delirious. Older age, previous stroke, higher EuroSCORE II, lower preoperative Mini-Mental Status Examination, and more substantial absolute postoperative cerebral oxygen saturation decreases were independently associated with postoperative delirium incidence. Conclusions: Postoperative delirium in older patients undergoing cardiac surgery is associated with absolute decreases in postoperative cerebral oxygen saturation. These differences appear most detectable after the onset of delirium.