Intraoperative neurological pupil index and postoperative delirium and neurologic adverse events after cardiac surgery: an observational study

Abstract

Neurological pupil index (NPi) calculated by automated pupillometry predicts clinical outcomes in critically ill patients. However, there are few data on intraoperative NPi and postoperative outcome after cardiac surgery. We evaluated the relationships between intraoperative NPi and clinical outcomes, such as delirium, in cardiac surgery patients. NPi was measured at baseline, after anesthesia induction, at 30 min intervals after initiation of cardiopulmonary bypass or anastomosis of coronary artery bypass graft, and at skin closure. Abnormal NPi was defined as one or more measurements of NPi < 3.0 during surgery. The worst intraoperative NPi was recorded, then multivariate logistic regression analysis was performed to evaluate the relationship between abnormal NPi and postoperative delirium following cardiac surgery. Among 123 included patients, postoperative delirium developed in 19.5% (24/123) of patients. Intraoperative abnormal NPi was significantly associated with postoperative delirium (odds ratio 6.078; 95% confidence interval 1.845-20.025; P = 0.003) after adjustment for Society of Thoracic Surgeons Predicted Risk of Mortality score, coronary artery disease, and use of calcium channel blockers. In conclusion, abnormal intraoperative NPi independently predicted postoperative delirium following cardiac surgery. Intraoperative application of pupillometry may have prognostic value for development of postoperative delirium, thereby enabling close surveillance and early intervention in high-risk patients.Registry number: ClinicalTrials.gov (NCT04136210).

Figure 1

Box plot of the worst neurological pupil index during surgery in patients with and without postoperative delirium. Horizontal line within the box indicates median value. Lower and upper boundaries of the box indicate 25th and 75th percentiles, respectively. Horizontal lines outside the box indicate the minimum and the maximum values of the data. Dots outside the box are outliers. P value between the groups was calculated using Mann–Whitney U test. NPi neurological pupil index.

Figure 2

Comparison of neurological pupil index at baseline and at the end of surgery in patients with and without postoperative delirium. CI confidence interval, NPi neurological pupil index.

Figure 3

Serial measures of neurological pupil index during surgery in patients with and without postoperative delirium. P value between the groups was calculated using linear mixed model. NPi neurological pupil index.