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In elderly patients, postoperative delirium (POD) is a common complication that is associated with prolonged hospital stay and increased mortality.1, 2 Patients suffering from POD show cognitive dysfunction, disorientation, and visual hallucinations that can complicate postoperative treatment and nursing care. Therefore, preoperative prediction of POD is important for the prevention and management of POD. Various risk factors for POD have been reported; these include aging, infections, drug ingestion or withdrawal, metabolic conditions, primary central nervous system disease, and toxic agents. However, the underlying pathogenic mechanisms of POD are poorly understood. Therefore, the most appropriate means of preventing and managing POD remain undetermined, and the preoperative prediction of POD had been difficult.3
The noise pareidolia test (NPT) is a newly developed method to evaluate the severity of visual hallucination.4 Pareidolia, which is a particular type of complex visual illusion, has been reported to be analogous to visual hallucinations in patients with dementia with Lewy bodies (DLB). NPT correlates well with visual hallucinations and is said to be useful for the diagnosis of DLB. Visual hallucination is a core clinical feature that is important in the differential diagnosis and prediction of treatment response in DLB.4 In this study, we analyzed the risk factors for POD in elderly patients undergoing elective abdominal major surgery and evaluated the usefulness of the NPT for preoperative prediction of POD.
This study enrolled 57 preoperative patients older than 70 years who were scheduled for elective hepatobiliary and pancreatic surgery between November 2015 and December 2016 at our hospital. The institutional review board of our hospital approved this study protocol. The 57 patients had a mean age of 78.0 years (range, 70-88 years); there were 42 men and 15 women. The preoperative diagnoses included hepatocellular carcinoma in 27, pancreatic cancer in 10, bile duct cancer in six, cancer of the ampulla of Vater in five, metastatic liver cancer in four, cholelithiasis in three, and duodenal cancer in two patients. The operative procedures were partial hepatectomy in 17, pancreaticoduodenectomy in 11, distal pancreatectomy in six, subsegmentectomy of the liver in five, right hepatectomy in four, left hepatectomy in four, cholecystectomy in four, and others in six patients; four of these procedures were performed by laparoscopy. The mean operative time was 277 minutes (range, 69-538...