The original study and this secondary analysis were approved by Nara Medical University Institutional Review Board, Kashihara, Nara, Japan (Number 2904). The need for informed consent was waived owing to the retrospective nature of this study.
Patients aged 20 years or older who underwent elective TUR-BT for bladder tumors under general anesthesia from April 2016 to November 2020 at our tertiary teaching hospital were eligible for enrolment in our original study. Patients with a preoperative diagnosis of dementia and who required additional procedures in addition to TUR-BT were excluded. Patients with missing data were also excluded from the analysis.
Age, sex, body mass index, preexisting medical conditions (hypertension, ischemic heart disease, symptomatic stroke, diabetes), pulmonary function (normal, obstructive lung disease, restrictive lung disease), plasma albumin, plasma creatinine, American Society of Anesthesiologists-Physical Status (ASA-PS), and preoperative administration of 5-ALA were obtained from the electric medical records. We defined patients taking antihypertensive drugs and oral diabetic drugs or injectable insulin as patients with hypertension and diabetes mellitus, respectively. Patients were considered to have obstructive lung disease if their forced expiratory volume 1.0 (s) % was <70%; restrictive lung disease was defined as a vital capacity of <80%. Patients with ischemic heart disease were defined as those having a history of coronary artery bypass graft and/or percutaneous coronary intervention. Intraoperative data including anesthetics (inhalation agents or propofol), intraoperative hypotension, and duration of anesthesia were also assessed. Intraoperative hypotension was defined as a mean arterial pressure value < 60 mmHg, in accordance with a recent review .
The primary outcome for this study was the incidence of POD and its associated factors occurring during the first 7 postoperative days or up to the day of discharge; these data were obtained using a chart-based method for the prediction of delirium . This method, which has been widely used to identify delirium after anesthesia and during intensive care, allows for the assessment of delirium during the evaluation period, including overnight [12,13,14]. The secondary outcome was the difference in postoperative length of stay categorized based on POD.
Data are presented as median [first quartile, third quartile] or n (%). Univariate analysis was performed using Fisher’s exact test or Mann–Whitney U-test for categorical or continuous variables, respectively. Multiple logistic regression analysis with all explanatory variables was used to identify variables associated with the primary outcome. In multiple logistic regression analysis, ASA-PS was divided into two groups, namely, ASA-PS 1 and 2 or ASA-PS 3; then, ASA-PS 3 was included as one of the covariates. Furthermore, the postoperative length of stay was compared between patients with POD or without POD using the Mann–Whitney U-test. p < 0.05 was considered statistically significant.
Sample size was not calculated due to the nature of a secondary analysis and was based on our original study; thus, the incidence of POD is expressed as a percentage, with the 95% confidence interval (CI) calculated using the Wald method. The number of cases ≥10 times the explanatory variable for the number of cases with few outcomes is recommended to perform the logistic regression analysis. In this study, of the covariates collected in our original study, only factors considered to be strongly associated with POD were analyzed; however, the number of these covariates exceed the recommended number. Thus, not only results of the logistic regression analysis, such as odds ratios and p values, but also those of the Hosmer–Lemeshow test and AUC were analyzed. The Hosmer–Lemeshow test was used to test the calibration of the model, and the area under the receiver operating characteristic curve (AUC) was computed as a descriptive tool for measuring model bias.
In 2020, a well-designed systematic review of postoperative delirium after urologic surgery was published ; however, few systematic reviews have evaluated POD after transurethral resection (TUR). Thus, in order to understand the current status of POD after TUR, we performed an additional search on July 11, 2021, using MEDLINE, Embase, PsycINFO, CINAHL, and Cochrane library to identify new studies published from January 23, 2020 (last day which the previous systematic review included in the search), to July 10, 2021, that evaluated POD after urological surgery. We then planned to extract studies focusing on TUR. Randomized controlled trials, prospective and retrospective observational studies, and systematic reviews with or without meta-analysis written in English were eligible for inclusion. The manuscript titles and abstracts were screened independently by two of the authors (SN and MI). Finally, inconsistencies were resolved by discussion. The full search strategy is presented in Supplemental Table 1.