The effect of preoperative cognitive impairment and type of vascular surgery procedure on postoperative delirium with associated cost implications

Abstract

Objective: Postoperative delirium (POD) has a high prevalence among vascular surgery patients, increasing morbidity, mortality, and length of stay. We prospectively studied preoperative risk factors for delirium that can be assessed by the surgical team to identify high-risk patients and assessed its impact on hospital costs.

Methods: There were 173 elective vascular surgery patients assessed preoperatively for cognitive function using the Montreal Cognitive Assessment (MoCA) and the Confusion Assessment Method for POD, which was verified by chart and clinical review. Demographic information, medications, and a history of substance abuse, psychiatric disorders, and previous delirium were prospectively recorded. An accompanying retrospective chart review of an additional 434 (elective and emergency) vascular surgery patients provided supplemental cost information related to sitter use and prolonged hospitalization secondary to three factors: delirium alone, dementia alone, and delirium and dementia.

Results: Prospective screening of 173 patients (73.4% male; age, 69.9 ± 10.97 years) identified that 119 (68.8%) had MoCA scores <24, indicating cognitive impairment, with 7.5% having severe impairment (dementia). Patients who underwent amputation had significantly (P < .000) lower MoCA scores (17 of 30) compared with open surgery and endovascular aneurysm repair patients (23.7 of 30). The incidence of delirium was 11.6% in the elective cohort. Regression analysis identified predictors of delirium to be type of surgical procedure, including lower limb amputation (odds ratio [OR], 16.67; 95% confidence interval [CI], 3.41-71.54; P < .000) and open aortic repair (OR, 5.33; 95% CI, 1.91-14.89; P < .000); cognitive variables (dementia: OR, 5.63; 95% CI, 2.08-15.01; P < .001); MoCA scores ≤15, indicating moderate to severe impairment (OR, 6.13; 95% CI, 1.56-24.02; P = .02); and previous delirium (OR, 2.98; 95% CI, 1.11-7.96; P = .03). Retrospective review (N = 434) identified differences in sitter needs for patients with both delirium and dementia (mean, 13.6 days), delirium alone (mean, 3.9 days), or dementia alone (mean, <1 day [17.7 hours]). Fifteen patients required >200 hours (8.3 days), accounting for 69.7% of sitter costs for the surgical unit; 43.7% of costs were accounted for by patients with pre-existing cognitive impairment.

Conclusions: POD is predicted by type of vascular surgery procedure, impaired cognition (MoCA), and previous delirium. Costs and morbidity related to delirium are greatest for those with impaired cognitive burden. Preoperative MoCA screening can identify those at highest risk, allowing procedure modification and informed care.

Keywords: Cognition; Delirium; MoCA; Preoperative; Vascular surgery.