Emergence from general anaesthesia and evolution of delirium signs in the post-anaesthesia care unit

Abstract

Background: Emergence from anaesthesia is often accompanied by signs of delirium, including fluctuating mental status and inattention. The evolution of these signs of delirium requires investigation since delirium in the post-anaesthesia care unit (PACU) may be associated with worse outcomes.

Methods: Adult patients emerging from anaesthesia were assessed for agitated emergence in the operating room using the Richmond Agitation-Sedation Scale (RASS). The Confusion Assessment Method for the Intensive Care Unit was then used to evaluate delirium signs at PACU admission and during PACU stay at 30 min, 1 h, and discharge. Signs consistent with delirium were classified as hyperactive vs hypoactive based upon a positive CAM-ICU assessment and the concomitant RASS score. Multivariable logistic regression was utilized to assess potential risk factors for delirium during PACU stay including age, American Society of Anesthesiologists classification, and opioid and benzodiazepine exposure.

Results: Among 400 patients enrolled, 19% had agitated emergence. Delirium signs were present at PACU admission, 30 min, 1 h, and PACU discharge in 124 (31%), 59 (15%), 32 (8%), and 15 (4%) patients, respectively. In patients with delirium signs, hypoactive signs were present in 56% at PACU admission and in 92% during PACU stay. Perioperative opioids were associated with delirium signs during PACU stay (P=0.02).

Conclusions: A significant proportion of patients develop delirium signs in the immediate postoperative period, primarily manifesting with a hypoactive subtype. These signs often persist to PACU discharge, suggesting the need for structured delirium monitoring in the PACU to identify patients potentially at risk for worse outcomes in the postoperative period.

Keywords: anaesthesia; complications; delirium.

Fig 1

Probability of PACU Delirium Signs by Opioid Administration. Total preoperative, intraoperative, and post-anaesthesia care unit (PACU) opioid administration was independently associated with delirium signs during PACU stay, defined as a positive Confusion Assessment Method for the ICU at 30 min, at 1 h, or at discharge from the PACU. The solid line demonstrates the predicted probability of developing PACU delirium signs according to fentanyl equivalents received, with the pink ribbon indicating the 95% confidence interval. This association was most meaningful when examined between the 5th (50 μg fentanyl) and 50th (383 μg fentanyl) percentiles of opioid administration (common dose ranges for opioids in patients undergoing general anaesthesia) in our cohort, such that a patient receiving opioids equivalent to 383 μg fentanyl would have over 6 times the adjusted odds of developing delirium signs during PACU stay than a patient receiving 50 μg fentanyl (odds ratio [OR] 6.2, 95% CI 1.7, 22.1). Alternatively, when comparing the 50th to the 95th percentiles of opioid administration within our cohort, a patient receiving 383 μg fentanyl would have similar adjusted odds of developing delirium signs during PACU stay than a patient receiving 850 μg fentanyl (OR 0.88, 95% CI 0.45, 1.71). The lack of association at the higher doses could reflect a ceiling effect of the role of opioids in contributing to delirium signs or be a manifestation of fewer patients receiving such large doses.