To compare brain injury biomarker release levels between two different cardiopulmonary bypass (CPB) flow rates in elective cardiac surgery and to explore differences in postoperative delirium between groups and associations between age, sex, CPB time, oxygen levels, and near-infrared spectroscopy, and biomarker levels.

A randomized controlled substudy trial

Sahlgrenska University Hospital, Sweden

Forty patients undergoing elective cardiac surgery with CPB

Patients were assigned at random to either a standard (2.4 L/min/m²) or a high (2.9 L/min/m²) CPB flow rate.

Glial fibrillary acidic protein, neurofilament light chain, total-tau, and phosphorylated-tau217 were sampled in plasma before anesthesia induction, after 60 minutes on CPB, and at 30 minutes, 24 hours, and 72 hours post-CPB. Mixed models for repeated measures were used to analyze differences in biomarker levels between groups and to assess relationships, which showed no differences between the 2 flow rate groups. There also was no difference in the occurrence of delirium between the 2 groups. Associations were found between age and increased neurofilament light chain levels. Female sex, oxygen delivery >330 mL/min/m², and near-infrared spectroscopy level >60% were associated with lower biomarker levels.

An increased flow rate did not have any significant effects on biomarker levels compared to a standard flow rate. Several associations were identified between treatment characteristics and biomarker levels. No difference in delirium was seen.