Impact of prognostic nutritional index on the occurrence of post-operative delirium after total knee arthroplasty

Purpose

Delirium has been reported to cause delayed functional recovery, prolonged hospitalization, future institutionalization, increased mortality, and increased healthcare costs. However, there are no reports on how prognostic nutritional index (PNI), Controlling Nutritional Status (CONUT) score, and geriatric nutritional risk index (GNRI) are related to delirium after total knee arthroplasty (TKA). This study aimed to identify risk factors for post-operative delirium after TKA using various pre-operative nutritional assessments (PNI, CONUT score, and GNRI).

Methods

In total, 289 patients who underwent primary TKA between September 2011 and April 2022 in our institute (Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan) were enrolled. Patients were divided into two groups: those who developed post-operative delirium (Group D), and those who did not (Group ND). Pre-operative risk factors, including nutritional indices, for post-operative delirium were evaluated.

Results

Group D comprised 16 participants, while Group ND comprised 273 participants. Comparisons between the two groups revealed significant differences in age, PNI, CONUT score, GNRI, and history of cerebrovascular disease. Multiple logistic regression analysis revealed that significant risk factors for delirium after TKA were age, PNI, and history of cerebrovascular disease. A receiver operating characteristic curve indicated that the cutoff values for delirium were 47.4 for PNI (sensitivity, 0.810; specificity, 0.875) and 78.5 years for age (sensitivity, 0.813; specificity, 0.722).

Conclusions

Risk factors for post-operative delirium after TKA were PNI <47.4, age >78.5 years, and history of cerebrovascular disease. Patients exceeding these pre-operative cutoff values or with a history of cerebrovascular disease should receive counseling about delirium before surgery.