Purpose: Indications for the surgical treatment of elderly patients have been increasing. Postoperative central nervous system dysfunction, including delirium, is one of the most common complications in elderly surgical patients. The relationship between patient factors, including cerebral oxygen saturation, and the incidence of postoperative delirium was evaluated.
Methods: Twenty American Society of Anesthesiologists (ASA) physical status I-II patients, older than 65 years, scheduled for elective abdominal surgery were enrolled in the study. The patients' cognitive function was assessed, using the Hasegawa dementia score (HDS) and kana-hiroi test, on the day before surgery and then again 1 week after the surgery. Regional cerebral oxygen saturation (rSO2) was continuously monitored during the surgery, using near-infrared spectroscopy (INVOS 3100). General anesthesia was induced with 3 mg x kg(-1) thiopental and 5% sevoflurane. After tracheal intubation, the sevoflurane concentration was adjusted to maintain the bispectral index (BIS) value between 45 and 60. Postoperative delirium was diagnosed if DSM IV criteria were present and the patient scored 12 or more points on the Delirium Rating Scale.
Results: After surgery, 5 (25%) patients developed delirium. The age in the delirium (+) group (76 +/- 4 years) was significantly higher than that in delirium (-) group (68 +/- 3 years). Preoperative and postoperative HDS did not differ between the groups. The score on the preoperative kana-hiroi-test in the delirium (+) group (16 +/- 5) was significantly lower than that in the delirium (-) group (32 +/- 10). There were no significant differences between preoperative and postoperative kana-hiroi test scores in either group. Baseline rSO2 in the delirium (+) group (60 +/- 5%) was significantly lower than that in the delirium (-) group (66 +/- 7%). However, there were no significant differences between the groups in the rSO2 after the start of surgery.
Conclusion: Patients' age, low preoperative kana-hiroi test score, and low preoperative rSO2 were important risk factors for postoperative delirium.