Bispectral index use, malignancy tied to higher incidence of PACU delirium

A Singapore study has observed a low incidence of postanaesthesia care unit (PACU) delirium among patients undergoing noncardiac surgery. The use of bispectral index (BIS) and a history of malignancy are both significantly associated with a higher incidence of PACU delirium, which also results in a longer duration of PACU stay.

“In this first local study, the incidence of PACU delirium was 3.8 percent, increasing to 6.2 percent in those aged >65 years,” the researchers said. “Understanding these risk factors will form the basis for which protocols can be established to optimize resource management and prevent long-term morbidities and mortality in PACU delirium.”

A total of 478 eligible patients undergoing major surgery in three public hospitals in Singapore were audited over 1 week. The researchers assessed patients for delirium 30‒60 min following their arrival in PACU using the nursing delirium screening scale (Nu-DESC), with a score of ≥2 indicative of delirium.

Overall, the incidence of PACU delirium was 3.8 percent (18 out of 478 patients). The incidence slightly rose to 6.2 percent among patients aged >65 years (nine out of 146 patients). PACU delirium occurred more frequently among women, patients with malignancy, and those who underwent longer operations. [Singapore Med J 2023;64:728-731]

In logistic regression analysis, the presence of malignancy (p<0.001) and use of bispectral index (p<0.001) significantly correlated with a greater PACU delirium incidence.

“Our study reported a low incidence of 3.8 percent, which could reflect the relatively young age of the postoperative population that was assessed within the time frame across different hospital systems,” the researchers said.

“In comparison, in other studies involving elderly orthopaedic trauma patients, up to 50 percent of patients have been reported to develop PACU delirium,” they added. [Minerva Anestesiol 2011;77:715-722; Anesth Analg 2005;101:1215-1220]

One notable finding of the current study was the association between bispectral index use and a higher incidence of PACU delirium. The relationship, however, appeared to be not causal in nature, according to the researchers.

Previous studies have shown that bispectral index-guided anaesthesia could lower the rates of postoperative delirium (POD), especially among older patients. [Clin Interv Aging 2019;14:1095-1117; J Neurosurg Anesthesiol 2013;25:33-42]

“Although it is more common for local anaesthesiologists to utilize bispectral index for older patients, there was no evidence that this prevented PACU delirium,” the researchers said. “Also, we did not have data on whether bispectral index was used to guide the depth of anaesthesia.”

PACU delirium is a predictor of POD, making it crucial to have early detection and effective triage of patients. Those with PACU delirium and higher Nu-DESC scores were more likely to need greater resources and be discharged from PACU to high-dependency unit or intensive care unit.

“Implementing Nu-DESC in the PACU unit will lay the foundation for using it as a standard of care and optimizing resource management for patients in the postoperative period,” the researchers said.