Serum-neuroproteins, near-infrared spectroscopy, and cognitive outcome after beach-chair shoulder surgery: observational cohort study analyses

BACKGROUND: Cerebral hypoxia may occur during surgery but currently used cerebral oxygenation saturation (rSO2) monitors remain controversial with respect to improving clinical outcome. Novel neuroprotein biomarkers are potentially released into systemic circulation and combined with near-infrared spectroscopy (NIRS) could clarify the presence of per-operative cerebral hypoxia. We investigated changes to serum-neuroprotein concentrations postsurgically, paired with NIRS and cognitive outcome, in patients operated in the beach chair position (BCP).

METHODS: A prospective cohort in 28 shoulder surgery patients placed in the BCP. Blood samples were collected before induction of anaesthesia, and 2 hours and 3-5 days postoperatively. We analysed blood-levels of biomarkers including tau and neurofilament light (NFL). We post hoc assessed the cross-wise relationship between biomarker levels and postsurgical changes in cognitive function and intraoperatively monitored rSO2 from NIRS.

RESULTS: Serum-NFL decreased from 24.2 pg/mL to 21.5 (P=0.02) 2 hours postoperatively, then increased to 27.7 pg/mL on day 3-5 (P=0.03). Conversely, s-tau increased from 0.77 pg/mL to 0.98 (2 h), then decreased to 0.81 on day 3-5 (P=0.08). In 14/28 patients, episodic rSO2 below 55% occurred, and the duration <55% was correlated to change in s-tau (P<0.05). The cognitive function z-score at 1 week and 3 mo. correlated to the change in tau (P=0.01), but not to NFL.

CONCLUSION: Some biomarkers were significantly changed with surgery in the beach chair position. The change was at some points associated to postoperative cognitive decline, and to intraoperative low rSO2. (237).